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Definite energy in Quantum Mechanics According to Phillips' "Introduction to Quantum Mechanics", Chapter 4 "an eigenfunction of the Hamiltonian always describes a state of definite energy". But how can that be without violating the uncertainty principle? Energy and time are conjugate so neither can be zero and give $h/4\pi$. The reason for solving the eigenvalue problem is that it gives definite energy, i.e. no uncertainty. Why is that a good thing? | Something special about energy eigenstates when it comes to time evolution? A particle is subject to an infinite square well potential with $$V(x)= \begin{cases} 0 & −a \lt x \lt a\\ \infty & \,\,\,\,\text{otherwise} \end{cases}$$ At a time $t=0$ its wavefunction is given by $$\psi(x, t=0)=\frac{1}{\sqrt{5a}}\cos\left(\frac{\pi x}{2a}\right)+\frac{2}{\sqrt{5a}}\sin\left(\frac{\pi x}{a}\right)$$ (a) What are the possible results of an energy measurement at $t = 0$, and with what probabilities? Re-writing the terms in $\psi(x,t=0)$ as $$u_1(x)=a^{-1/2}\cos\left(\frac{\pi x}{2a}\right)\qquad \text{&} \qquad u_2(x)=a^{-1/2}\sin\left(\frac{\pi x}{a}\right)$$ such that $$\psi(x,t=0)= \frac{1}{\sqrt{5}}u_1(x)+\frac{2}{\sqrt{5}}u_2(x)$$ with energies $$E_1=\frac{\hbar^2 \pi^2}{8ma^2}\qquad \text{&} \qquad E_2=\frac{\hbar^2 \pi^2}{2ma^2}$$ and probabilities $$P(E_1)=\frac15 \qquad \text{&} \qquad P(E_2)=\frac45$$ (b) If no measurement is performed, what is the wavefunction $\psi(x, t)$ at all times $t$? What are the possible energies and their probabilities if a measurement is first performed at time $t$? At a time $t$ the wavefunction is given by $$\psi(x, t=0)=\frac{1}{\sqrt{5a}}\cos\left(\frac{\pi x}{2a}\right)\exp\left(\frac{-i E_1 t}{\hbar}\right)+\frac{2}{\sqrt{5a}}\sin\left(\frac{\pi x}{a}\right)\exp\left(\frac{-i E_2 t}{\hbar}\right)$$ The problem is that I cannot answer the second part of the question (b). The answer states that: Because the two terms are energy eigenstates, the relative probabilities do not change and are as in the previous part. I have some questions about the above statement: why does an "energy eigenstate" mean that the probablities don't change with time? Or, put in another way, does a "momentum eigenstate" (for example) have constant relative probabilities when measured at any time? The answer seems to be implying there is something special about energy eigenstates when it comes to time evolution. The eigenvalues of energy measurements don't seem to change regardless of how many times you measure them, and no matter how long you wait until you measure them. I'm not sure if this is the case, but could someone please explain why all quantum operators (except Hamiltonian) do not exhibit this behaviour. | Question regarding the validity of the big bounce I have several questions regarding the "big bounce" theory. It appears to be popular among LQG researchers. My questions are as as follows. 1) How one reconciles it with the fact that it is now experimentally established that the universe is expanding in an accelerating manner? 2) The entropy of the universe should have been very very low (maybe zero) at the time of the big bang/ big bounce. What was the entropy "before" that event? Was it even lower? If it was lower then doesn't that mean entropy decreases indefinitely? On the other hand if we accept the entropy was higher then doesn't that violate the second law of thermodynamics? 3) What observational evidence can confirm pre-bounce physics? According to GR there are some points near the bang/bounce where one simply can't easily define time in a meaningful way. Even for a quantum gravity theory, is it possible for any theory to extrapolate itself "before" the "bounce"? If there are no observational consequences after the bounce shouldn't one apply Occam's razor? | eng_Latn | 11,100 |
How does the electron know to "release" the photon at the same angle at which it got absorbed? : In classical electrodynamics, light is considered as an electromagnetic wave, which is described by Maxwell's equations. Light waves incident on a material induce small oscillations of polarisation in the individual atoms (or oscillation of electrons, in metals), causing each particle to radiate a small secondary wave in all directions, like a dipole antenna. All these waves add up to give specular reflection and refraction, according to the Huygens–Fresnel principle. My question is, how do all the waves add up to give the direction of angle-in equal to angle-out if they are going in all directions? Also, in reflection does the photon get absorbed and re-emitted or does it act like a dipole antenna? | Explain reflection laws at the atomic level The "equal angles" law of refection on a flat mirror is a macroscopic phenomenon. To put it in anthropomorphic terms, how do individual photons know the orientation of the mirror so as to bounce off in the correct direction? | Can a quasiclassical electron wave packet in elliptic orbit be formed from bound hydrogen-like eigenstates? Position probability densities of eigenstates of hydrogen-like systems have axial symmetry, so that the wavefunction too much resembles the circular orbits in Bohr's model. I'd like to have a demonstration of correspondence principle, where an electron would be localized to look somewhat like a classical particle, and move in an elliptic (non-circular) orbit around a nucleus. It seems though that if we try to make a wave packet too localized, then it'll disintegrate (get scattered by the nucleus) too fast to see anything resembling an elliptic orbit. OTOH, if we take it too spread out, it'll have to be quite far from the nucleus so as to avoid hitting it, and thus it'll have high total energy, which may appear to be above ionization threshold (at least partially), after which it'd be quite hard to analytically calculate evolution of the wave packet. Thus my question is: is it possible to form a more or less localized wave packet, which would (on average) move in an obviously-elliptic orbit (major/minor axes ratio of 4:3 or higher), and only require bound states to fully represent it? If yes, then what properties (FWHM, apocenter, angular momentum etc.) should it have for this to be possible? | eng_Latn | 11,101 |
Why does water fall sort of helically from a cup? I noticed today that if I took a glass of water and poured it out slowly (small tilt to the cup), it flowed rather smoothly, but when I increased the tilt the water flowed in a sort of helical manner, this could be observed in the given image in the case of a tap: What could the possible reason for such a flow be? Considering (mentioned in comment), could it be that if speed of water flow be quick enough that the flow doesn't break down to form drops. This is what my limited non mathematical understanding brought me to. | Wavy stream of liquid While pouring a liquid into a glass from a bottle, some streams have a wavy shape, like the one in the following photo: What causes the stream to be of such a shape? | Can a quasiclassical electron wave packet in elliptic orbit be formed from bound hydrogen-like eigenstates? Position probability densities of eigenstates of hydrogen-like systems have axial symmetry, so that the wavefunction too much resembles the circular orbits in Bohr's model. I'd like to have a demonstration of correspondence principle, where an electron would be localized to look somewhat like a classical particle, and move in an elliptic (non-circular) orbit around a nucleus. It seems though that if we try to make a wave packet too localized, then it'll disintegrate (get scattered by the nucleus) too fast to see anything resembling an elliptic orbit. OTOH, if we take it too spread out, it'll have to be quite far from the nucleus so as to avoid hitting it, and thus it'll have high total energy, which may appear to be above ionization threshold (at least partially), after which it'd be quite hard to analytically calculate evolution of the wave packet. Thus my question is: is it possible to form a more or less localized wave packet, which would (on average) move in an obviously-elliptic orbit (major/minor axes ratio of 4:3 or higher), and only require bound states to fully represent it? If yes, then what properties (FWHM, apocenter, angular momentum etc.) should it have for this to be possible? | eng_Latn | 11,102 |
So I'm reading about bound systems right now in my quantum text. It is beginning to explain why energy must be quantized, and is doing so by introducing the reader to the one dimensional "quanton in a box". Essentially it shows this: For a region of 0 potential energy, with infinite potential energy everywhere else, a particle is "free" within the region of 0 potential energy. This means that the particles wave function must go to zero at these "boudaries", and therefore resemble a standing wave between the potential energy bounds. Because the wavefunction must be zero at the ends, the Dr Broglie wavelength must be so that an integer number of half-wavelengths fits inbetween the regions of infinite potential. Therefore, the energy of a particle (quanton) must be so to satisfy this, and cannot be any arbitrary value. First of all, the more board question: why, then would an electron that is outside of a bound system be quantized? Or any other particle that is outside of a bound system (atomic nucleus, etc.)? Secondly, the question that I am more interested in: the only reason that a classical standing wave in a string results in the way it does is be cause f resonance; the string resists frequencies that do not match a natural harmonic of the material, and accepts very well frequencies which do match. So then isn't the fact of energy quantization a direct consequence of the phenomenon of resonance? It must be. But then, what is the material that is experiencing this resonance? For an electron, which could be described as a "matter-wave", would the Higgs field, itself, be resonating? Or something else? | Given some potential $V$, we have the eigenvalue problem $$ -\frac{\hbar^2}{2m}\Delta \psi + V\psi = E\psi $$ with the boundary condition $$ \lim_{|x|\rightarrow \infty} \psi(x) = 0 $$ If we wish to seek solutions for $$ E < \lim_{|x|\rightarrow \infty}V(x), $$ I find textbooks like Sakurai and others assert that (without proof) set of all such eigenvalues $E$ that admits nontivial solutions is discrete, which gives us liberty to index them with natural numbers (principal quantum numbers). Can anyone help me with a little elaboration of this mathematical fact ? As a student of mathematics, I know that compact operators have discrete spectrums, so for the operator $ T : L^2 \rightarrow L^2 $given as $$ T(\psi) = -\frac{\hbar^2}{2m}\Delta \psi + V\psi. $$ Are there methods to show that $T$ is compact? Or possibly other ways to establish discreteness of its eigenspectrum? | The new Top-Bar does not show reputation changes from Area 51. | eng_Latn | 11,103 |
Nuclear stability Why does increasing the number of neutrons in a nucleus make it more unstable? I know that adding more protons increases electrostatic repulsion, therefore the nucleus is more unstable, but as neutrons are neutral what effect does adding more have? | Adding many more neutrons to a nucleus decreases stability? If you take any large nucleus and add protons to it, the electrostatic repulsion between them will make the nucleus more unstable, because the electrostatic force between them is more repulsive at a greater distance than the strong force is attractive So how come if you add more neutrons, which don't have a charge and so there is no electrostatic force, the nucleus still becomes more unstable? Also why aren't there groups of neutrons bound together, so purely neutron nuclei (because they are neutral, I'm guessing they couldn't form atoms, because of the electrons needed for an atom) | Can virtual particles be thought of as off-shell Fourier components of a field? I just found blog post, which gives an interpretation of virtual particles I haven't seen before. Consider a 1D system of springs and masses, where the springs are slightly nonlinear. A "real particle" is a regular $\cos(kx-\omega t)$ wavepacket moving through the line, where $\omega$ satisfies the dispersion relation $\omega = \omega(k)$. When two real particles collide, the region where they collide temporarily looks really weird, as they interact nonlinearly, pulling and pushing on each other. Formally, we can write this weird region as the sum of a bunch of $\cos(kx-\omega t)$ waves, but there's no guarantee they'll have the right dispersion relation. Thus, each term in the resulting expansion is a off-shell "virtual particle". If you add up all the virtual particles, you get the actual intermediate field state, which is just a weird ripple in the field where the two particles are interacting. As another example, consider the statement "a static EM field is made of virtual particles". Under this interpretation, what that really means is, "a static field (e.g. $1/r^2$) is not equal to $\cos(kx-\omega t)$, but may be expanded in terms of such sinusoids", which is much less mysterious sounding. In fact, this is exactly what we do when we consider scattering off a potential in normal QM, e.g. in the Born approximation. The above gives some intuition for what a 'virtual particle' means in classical field theory. They are the Fourier components of the field with $(\omega, k)$ not satisfying the dispersion relation, and they are useful in classical perturbation theory. However, they are not propagating degrees of freedom, so they only appear during interactions. The picture above is entirely classical. Does this picture generalize to quantum field theory, giving a physical intuition for virtual particles there? | eng_Latn | 11,104 |
Hamiltonian cycle and Euler Cycle. When $G = K_n, n \ge 3$ and $n$ is odd, then from the edges of the $G$ can be built edge-disjoint Hamiltonian cycles. Is it true? | Hamiltonian Cycle Problem At the moment I'm trying to prove the statement: $K_n$ is an edge disjoint union of Hamiltonian cycles when $n$ is odd. ($K_n$ is the complete graph with $n$ vertices) So far, I think I've come up with a proof. We know the total number of edges in $K_n$ is $n(n-1)/2$ (or $n \choose 2$) and we can split our graph into individual Hamiltonian cycles of degree 2. We also know that for n vertices all having degree 2, there must consequently be $n$ edges. Thus we write $n(n-1)/2 = n + n + ... n$ (here I'm just splitting $K_n$'s edges into some number of distinct Hamiltonian paths) and the deduction that $n$ must be odd follows easily. However, the assumption I made - that we can always split $K_n$ into Hamiltonian paths of degree 2 if $K_n$ can be written as a disjoint union described above - I'm having trouble proving. I've only relied on trying different values for $n$ trials and it hasn't faltered yet. So, I'm asking: If it is true, how do you prove that if $K_n$ can be split into distinct Hamiltonian cycles, it can be split in such a way that each Hamiltonian cycle is of degree 2? | Can a quasiclassical electron wave packet in elliptic orbit be formed from bound hydrogen-like eigenstates? Position probability densities of eigenstates of hydrogen-like systems have axial symmetry, so that the wavefunction too much resembles the circular orbits in Bohr's model. I'd like to have a demonstration of correspondence principle, where an electron would be localized to look somewhat like a classical particle, and move in an elliptic (non-circular) orbit around a nucleus. It seems though that if we try to make a wave packet too localized, then it'll disintegrate (get scattered by the nucleus) too fast to see anything resembling an elliptic orbit. OTOH, if we take it too spread out, it'll have to be quite far from the nucleus so as to avoid hitting it, and thus it'll have high total energy, which may appear to be above ionization threshold (at least partially), after which it'd be quite hard to analytically calculate evolution of the wave packet. Thus my question is: is it possible to form a more or less localized wave packet, which would (on average) move in an obviously-elliptic orbit (major/minor axes ratio of 4:3 or higher), and only require bound states to fully represent it? If yes, then what properties (FWHM, apocenter, angular momentum etc.) should it have for this to be possible? | eng_Latn | 11,105 |
Unclear equation in my scriptum (perhaps cauchy-product) Hi the following equation in my scriptum seems unclear. I think it has something to do with cauchy-product but i dont know | Sum of a power series $n x^n$ I would like to know: How come that $$\sum_{n=1}^\infty n x^n=\frac{x}{(x-1)^2}$$ Why isn't it infinity? | Why can we treat quantum scattering problems as time-independent? From what I remember in my undergraduate quantum mechanics class, we treated scattering of non-relativistic particles from a static potential like this: Solve the time-independent Schrodinger equation to find the energy eigenstates. There will be a continuous spectrum of energy eigenvalues. In the region to the left of the potential, identify a piece of the wavefunction that looks like $Ae^{i(kx - \omega t)}$ as the incoming wave. Ensure that to the right of the potential, there is not piece of the wavefunction that looks like $Be^{-i(kx + \omega t)}$, because we only want to have a wave coming in from the left. Identify a piece of the wavefunction to the left of the potential that looks like $R e^{-i(kx + \omega t)}$ as a reflected wave. Identify a piece of the wavefunction to the right of the potential that looks like $T e^{i(kx - \omega t)}$ as a transmitted wave. Show that $|R|^2 + |T|^2 = |A|^2$. Interpret $\frac{|R|^2}{|A|^2}$ as the probability for reflection and $\frac{|T|^2}{|A|^2}$ as the probability for transmission. This entire process doesn't seem to have anything to do with a real scattering event - where a real particle is scattered by a scattering potential - we do all our analysis on a stationary waves. Why should such a naive procedure produce reasonable results for something like Rutherford's foil experiment, in which alpha particles are in motion as they collide with nuclei, and in which the wavefunction of the alpha particle is typically localized in a (moving) volume much smaller than the scattering region? | eng_Latn | 11,106 |
Hessian and Ricci Curvature I just came across a term called the hessian and read that it represents the local curvature of a function at a point. So, if it represents local curvature, then is there any way the Hessian can be calculated in terms of the Ricci Curvature? | Relation bewteen Hessian Matrix and Curvature According to , It describes the local curvature of a function. AFAIK, for one-variable function $f(x)$, its local curvature is $$\kappa = \frac{|f''|}{(1 + f'^2)^{3/2}},$$ and its Hessian matrix is $$\mathcal{Hess}(f) = [f''],$$ right? And here is my problem, I think the local curvature is not just described by its Hessian matrix, because $f'$ also has its role in it, doesn't it? And furthermore, for 2-variable function $f(x,y)$, its Hessian matrix is $$\mathcal{Hess}(f) = \left[ \begin{array}{cc} f_{xx}'' & f_{xy}'' \\ f_{xy}'' & f_{yy}'' \end{array} \right].$$ How does it relate to the local curvature of $f(x,y)$? | Can a quasiclassical electron wave packet in elliptic orbit be formed from bound hydrogen-like eigenstates? Position probability densities of eigenstates of hydrogen-like systems have axial symmetry, so that the wavefunction too much resembles the circular orbits in Bohr's model. I'd like to have a demonstration of correspondence principle, where an electron would be localized to look somewhat like a classical particle, and move in an elliptic (non-circular) orbit around a nucleus. It seems though that if we try to make a wave packet too localized, then it'll disintegrate (get scattered by the nucleus) too fast to see anything resembling an elliptic orbit. OTOH, if we take it too spread out, it'll have to be quite far from the nucleus so as to avoid hitting it, and thus it'll have high total energy, which may appear to be above ionization threshold (at least partially), after which it'd be quite hard to analytically calculate evolution of the wave packet. Thus my question is: is it possible to form a more or less localized wave packet, which would (on average) move in an obviously-elliptic orbit (major/minor axes ratio of 4:3 or higher), and only require bound states to fully represent it? If yes, then what properties (FWHM, apocenter, angular momentum etc.) should it have for this to be possible? | eng_Latn | 11,107 |
How can I orient particles on a round object? This is a question, that came up whilst working on a scientific representation of a cell membrane. In the following image you can see the particle system applied to a plane: What I now want to do is to apply that particle system to a cylinder or circular object, which will show the cross-section of a vesicle. The particles should therefore all face outwards from the origin point of the circle. In the Rotation menu of the particle system there is no option for the particle to be orientated 90° away from the surface. Here is a bad sketch of how it should look. Q: How can I orient particles on a round object? | Scientific visualization - How to replicate instances around a sphere? I want to replicate a protein structure around an icosahedron. Basically a vesicle of protein structure is what we want: When I am instancing the protein structure using each vertex of the icosahedron it looks like: However, the tails are supposed to be directed towards the center. How can I make that work? | Can virtual particles be thought of as off-shell Fourier components of a field? I just found blog post, which gives an interpretation of virtual particles I haven't seen before. Consider a 1D system of springs and masses, where the springs are slightly nonlinear. A "real particle" is a regular $\cos(kx-\omega t)$ wavepacket moving through the line, where $\omega$ satisfies the dispersion relation $\omega = \omega(k)$. When two real particles collide, the region where they collide temporarily looks really weird, as they interact nonlinearly, pulling and pushing on each other. Formally, we can write this weird region as the sum of a bunch of $\cos(kx-\omega t)$ waves, but there's no guarantee they'll have the right dispersion relation. Thus, each term in the resulting expansion is a off-shell "virtual particle". If you add up all the virtual particles, you get the actual intermediate field state, which is just a weird ripple in the field where the two particles are interacting. As another example, consider the statement "a static EM field is made of virtual particles". Under this interpretation, what that really means is, "a static field (e.g. $1/r^2$) is not equal to $\cos(kx-\omega t)$, but may be expanded in terms of such sinusoids", which is much less mysterious sounding. In fact, this is exactly what we do when we consider scattering off a potential in normal QM, e.g. in the Born approximation. The above gives some intuition for what a 'virtual particle' means in classical field theory. They are the Fourier components of the field with $(\omega, k)$ not satisfying the dispersion relation, and they are useful in classical perturbation theory. However, they are not propagating degrees of freedom, so they only appear during interactions. The picture above is entirely classical. Does this picture generalize to quantum field theory, giving a physical intuition for virtual particles there? | eng_Latn | 11,108 |
In normalising the complete wavefunction of a free partcile; $V(x)=0$ we arrive at $\int_{-\infty}^{\infty}\Psi_{k} ^\dagger\Psi_{k}dx=|A|^{2}\int_{-\infty}^{\infty}dx=|A|^{2}\left(\infty\right)$ Which implies that this wave function is not normalisable. Mathematically, it is not normalisable but that's as far as my understanding goes. I would like to see a further and more related explanation for which a non-normalisable wave function implies that a free particle cannot exists in a stationary state and also that such a free particle does not have a definite energy. | The wavefunction $\Psi(x,t)$ for a free particle is given by $$\Psi(x,t) = A e^{i(kx-\frac{\hbar k}{2m}t)}$$ This wavefunction is non-normalisable. Does this mean that free particles do not exist in nature? Why then do we use free particles $\psi(\vec{x}) = e^{ikz}$, for example, in scattering theory? | Show that every large integer has a large prime-power factor That is, if $P(n)$ designates the largest number $p^a$ which divides $n$, then $\lim_{n\to\infty}P(n)=\infty.$ | eng_Latn | 11,109 |
Stationary State of Quantum Mechanics | How will a particle with energy less than $V_{\rm min}$ behave? | How does quantization solve the ultraviolet catastrophe? | yue_Hant | 11,110 |
How to make my Avid Elixir 1 hydraulic brakes more firm? I have a Specialized Carve Comp 2013, and the front brake is very squishy. The brake system is Avid Elixir 1 hydraulic disc brakes. I wanted to inquire if I need to buy a specific kit to firm up the brake lever, or if there is a simpler, less expensive solution. Please advise, thank you. | How do I bleed Avid Elixir brakes My bike has a set of Avid Elixir R hydraulic brakes. The front brake barely goes on when I pull the lever and the back brake feels pretty soft. I think I need to bleed them. How do I go about doing this? I think the brakes got like this because I pressed the brake level when the bike was upside down or when the wheel was removed putting the bike into my car. | Can a quasiclassical electron wave packet in elliptic orbit be formed from bound hydrogen-like eigenstates? Position probability densities of eigenstates of hydrogen-like systems have axial symmetry, so that the wavefunction too much resembles the circular orbits in Bohr's model. I'd like to have a demonstration of correspondence principle, where an electron would be localized to look somewhat like a classical particle, and move in an elliptic (non-circular) orbit around a nucleus. It seems though that if we try to make a wave packet too localized, then it'll disintegrate (get scattered by the nucleus) too fast to see anything resembling an elliptic orbit. OTOH, if we take it too spread out, it'll have to be quite far from the nucleus so as to avoid hitting it, and thus it'll have high total energy, which may appear to be above ionization threshold (at least partially), after which it'd be quite hard to analytically calculate evolution of the wave packet. Thus my question is: is it possible to form a more or less localized wave packet, which would (on average) move in an obviously-elliptic orbit (major/minor axes ratio of 4:3 or higher), and only require bound states to fully represent it? If yes, then what properties (FWHM, apocenter, angular momentum etc.) should it have for this to be possible? | eng_Latn | 11,111 |
binational map keeps smoothness? Let $E$ be a smooth curve, that is, one dimensional projective variety with dimension one, and Jacobi matrix is non-singular at any point. And suppose that the map $φ$, which sends $E$ to $E'$, is birational. Birational means there are two rational maps on both direction which composites identity. Then, can we say that $E'$ is smooth? | Birational map from elliptic curve keeps smoothness? Let $E$ be a elliptic curve that is , genus $1$ smooth curve with base point. And suppose that the map $φ$, which sends $E$ to $E'$, is birational. Birational means there are two rational maps on both direction which composites identity. Then, can we say that $E'$ is smooth? | Can a quasiclassical electron wave packet in elliptic orbit be formed from bound hydrogen-like eigenstates? Position probability densities of eigenstates of hydrogen-like systems have axial symmetry, so that the wavefunction too much resembles the circular orbits in Bohr's model. I'd like to have a demonstration of correspondence principle, where an electron would be localized to look somewhat like a classical particle, and move in an elliptic (non-circular) orbit around a nucleus. It seems though that if we try to make a wave packet too localized, then it'll disintegrate (get scattered by the nucleus) too fast to see anything resembling an elliptic orbit. OTOH, if we take it too spread out, it'll have to be quite far from the nucleus so as to avoid hitting it, and thus it'll have high total energy, which may appear to be above ionization threshold (at least partially), after which it'd be quite hard to analytically calculate evolution of the wave packet. Thus my question is: is it possible to form a more or less localized wave packet, which would (on average) move in an obviously-elliptic orbit (major/minor axes ratio of 4:3 or higher), and only require bound states to fully represent it? If yes, then what properties (FWHM, apocenter, angular momentum etc.) should it have for this to be possible? | eng_Latn | 11,112 |
Fractional quantum Hall effect Can someone explain the in layman's terms, I'm having some difficulty understanding it? | Quantum Hall effect for dummies In the past few days I've become increasingly intrigued by the QHE, mainly thanks to very interesting questions and answers that have appeared here. Unfortunately, I am as of yet very confused by all the (seemingly disparate) stuff I learned. First, here are some random points that I've been able to gather I(nteger)QHE occurs due to the presence of Landau levels IQHE is an embodiment of topological order and the states are characterized by the Chern number that tells us about topologically inequivalent Hamiltonians defined on the Brillouin zone IQHE requires negligible electron-electron interations and so is dependent on the presence of impurities that shield from Coulomb force F(ractional)QHE occurs because of formation of anyons. In this case Coulomb interaction can't be neglected but it turns out an effective non-interacting description emerges with particles obeying parastatistics and having fractional charge FQHE has again something to do with topology, TQFT, Chern-Simons theory, braiding groups and lots of other stuff FQHE has something to do with hierarchy states So, here are the questions Most importantly, do these points make sense? Please correct any mistakes I made and/or fill in other important observations How do explanations 1. and 2. of IQHE come together? Landau quantization only talks about electron states while topological picture doesn't mention them at all (they should be replaced by global topological states that are stable w.r.t. perturbations) How do explanations 4., 5. and 6. relate together Is there any accessible introductory literature into these matters? Do IQHE and FQHE have anything (besides last three letters) in common so that e.g. IQHE can be treated as a special case? My understanding (based on 3.) is that this is not the case but several points hint into opposite direction. That's also why I ask about both QHE in a single question | How to find hydrogen wave-functions? I have found the hydrogen wave functions and would now like to calculate the function that describes the orbitals so that I can plot this function and see how they look. I don't know how I can do that and it is crazy how I cannot find anything on the subject on the internet as if there was no relation between the wave functions and the orbitals. Could you please tell me what I need to do to get a function $r(\theta,\phi)$ out of my wave functions $\psi(r,\theta,\phi)$. | eng_Latn | 11,113 |
What does phase velocity physically represent, and why can it be superluminal? Phase velocity is defined as $v_p=\frac{\omega}{k}$ and is described in various textbooks as being the speed at which the phase of a wave propagates. If you have a wave train that is modulated by an envelope, then while the group velocity gives you the speed of the envelope the phase velocity gives you the speed of the wave within the envelope. Do $v_p$ and $v_g$ have any meaning if we are only considering one sinusoidal wave and not a superposition of such waves? I have been told that the speed of a single sinusoidal wave is its phase velocity, and that phase velocity is what we're really referring to when we talk about a wave's speed. However, how can phase velocity be greater than light if this is the case? The standard response seems to be that the group velocity is what determines the rate of information transfer, and it is this velocity that cannot exceed $c$. However, in special relativity a simple limit is set on the speed of any particle, and photons must travel only at speed $c$. If $v_p>c$ then does this not mean that the physical wave within the envelope is superluminal, and so the photons that comprise it are also superluminal? | In superluminal phase velocities, what is it that is traveling faster than light? I understand that information cannot be transmitted at a velocity greater than speed of light. I think of this in terms of the radio broadcast: the station sends out carrier frequencies $\omega_c$ but the actual content is carried in the modulated wave, the sidebands $\omega_c\pm\omega_m$. The modulation envelop has its group velocity and this is the speed at which information is being transmitted. We also know, for example, that x-rays in glass have a phase velocity which is greater than the speed of light in vacuum. My question is, what exactly is it that is travelling faster than the speed of light? EDIT: I know it couldn't be anything physical as its superluminal. My problem is, what is it that has absolutely no information content yet we associate a velocity with it. | Types of photon qubit encoding How many types of qubit encoding on photons exist nowadays? I know only two: Encoding on polarization: $$ \lvert \Psi \rangle = \alpha \lvert H \rangle + \beta \lvert V \rangle $$ $$ \lvert H \rangle = \int_{-\infty}^{\infty} d\mathbf{k}\ f(\mathbf{k}) e^{-iw_k t} \hat{a}^\dagger_{H}(\mathbf{k}) \lvert 0 \rangle_\text{Vacuum} $$ $$ \lvert V \rangle = \int_{-\infty}^{\infty} d\mathbf{k}\ f(\mathbf{k}) e^{-iw_k t} \hat{a}^\dagger_{V}(\mathbf{k}) \lvert 0 \rangle_\text{Vacuum} $$ Time-bin: $$ \lvert \Psi \rangle = \alpha \lvert 0 \rangle + \beta \lvert 1 \rangle $$ $$ \lvert 0 \rangle = \int_{-\infty}^{\infty} dz\ f\left(\frac{t -z/c}{\delta t_{ph}}\right) e^{-i w_0 (t-z/c)} \hat{a}^\dagger(z) \lvert 0 \rangle_\text{Vacuum} $$ $$ \lvert 1 \rangle = \int_{-\infty}^{\infty} dz\ f\left(\frac{t -z/c+\tau}{\delta t_{ph}}\right) e^{-i w_0 (t-z/c+\tau)} \hat{a}^\dagger(z) \lvert 0 \rangle_\text{Vacuum} $$ Is there anything else? | eng_Latn | 11,114 |
2s orbital wavefunction has non-zero probability at $r=0$? | Hydrogen radial wave function infinity at $r=0$ | Why is the $S_{z} =0$ state forbidden for photons? | eng_Latn | 11,115 |
"Equidistant" spectra in quantum mechanics | Is the harmonic oscillator potential unique in having equally spaced discrete energy levels? | referring to Eqn. 1a) and 1b) in a sentence as eqn. (1) | eng_Latn | 11,116 |
How to get Bohr model from Schroedinger equation? | How is Bohr's model related to electron cloud models via the correspondence principle? | Trouble understanding the Bohr model of the atom | eng_Latn | 11,117 |
Absorption spectrum of Hydrogen | Lyman and Balmer series | Hydrogen radial wave function infinity at $r=0$ | eng_Latn | 11,118 |
What is the time independent Schrödinger equation? | What does the time independent schrodinges equations signify? | How do you explain the equation to calculate the period of a pendulum? | eng_Latn | 11,119 |
what is Bloch theorem | Bloch theorem. A theorem that specifies the form of the wave functions that characterize electron energy levels in a periodic crystal. Electrons that move in a constant potential, that is, a potential independent of the position r, have wave functions that are plane waves, having the form exp(i k · r).he theorem that the lowest state of a quantum-mechanical system without a magnetic field can carry no current. (solid-state physics). The theorem that, in a periodic structure, every electronic wave function can be represented by a Bloch function. | One may appeal to Bloch's theorem in order to make headway in obviating this latter problem. Instead of being required to consider an infinite number of electrons, it is only necessary to consider the number of electrons within the unit cell (or half of this number if the electrons are spin degenerate).ne may appeal to Bloch's theorem in order to make headway in obviating this latter problem. Instead of being required to consider an infinite number of electrons, it is only necessary to consider the number of electrons within the unit cell (or half of this number if the electrons are spin degenerate). | eng_Latn | 11,120 |
Schrodinger's equation | How can I vertically align the numerators of two fractions? | How can one derive Schrödinger equation? | eng_Latn | 11,121 |
How is energy quantized? | Is frequency quantized in the black body spectrum? | $G/Z$ cannot be isomorphic to quaternion group | eng_Latn | 11,122 |
Localized blockage of nerve impulses at the myoneural junction. | Neural plasticity of mushroom body-extrinsic neurons in the honeybee brain. | Exogenous growth factors do not affect the development of individually cultured murine embryos | eng_Latn | 11,123 |
Origin of the dorsal root reflex. | Modulation of spinal reflexes by pyramidal tract stimulation in an in vitro brainstem-spinal cord preparation from the hamster | Porin channels in intact cells of Escherichia coli are not affected by Donnan potentials across the outer membrane. | eng_Latn | 11,124 |
An enhancement to velocity selective discrimination of neural recordings: Extraction of neuronal firing rates | A microfabricated nerve-on-a-chip platform for rapid assessment of neural conduction in explanted peripheral nerve fibers | Failure to clear persistent vaccine-derived neurovirulent poliovirus infection in an immunodeficient man | eng_Latn | 11,125 |
To investigate the pathways of noxious information in the spinal cord in humans, we recorded cortical potentials following the stimulation of A-delta fibers using a YAG laser applied to two cutaneous points on the back at the C7 and Th10 level, 4cm to the right of the vertebral spinous process. A multiple source analysis showed that four sources were activated; the primary somatosensory cortex (SI), bilateral parasylvian region (Parasylvian), and cingulate cortex. The activity of the cingulate cortex had two components (N2/P2). The mean peak latencies of the activities obtained by C7 and Th10 stimulation were 166.9 and 186.0 ms (SI), 144.3 and 176.8 ms (contralateral Parasylvian), 152.7 and 185.5 ms (ipsilateral Parasylvian), 186.2 and 215.8 ms (N2), and 303.0 and 332.3 ms (P2). Estimated spinal conduction velocities (CVs) of the respective activities were 16.8, 9.3, 8.7, 10.1 and 10.7 m/s. CV of SI was significantly faster than the others (P<0.05). Therefore, our results suggested that noxious signals were conveyed through at least two distinct pathways of the spinal cord probably reaching distinct groups of thalamic nuclei. Further studies are required to clarify the functional significance of these two pathways. | The ascending pain pathway consists of many complex neural structures, including specialized nociceptive receptors and peripheral nociceptive neurons in the dorsal root ganglion, spinal dorsal horn nociceptive and wide-dynamic range neurons, that play a role in the initial central neural processing for nociceptive information, several divergent relay stations (the thalamic nuclei and several nuclei in the brainstem) that properly mediate a variety of reflex reactions to painful stimuli, and are variously distributed among the thalamo-cortical and limbic circuits for sensory perception, learning, memory and other cognitive activity, and emotional responses. In addition to the ascending pain pathway, there are descending pathways that modulate pain by inhibiting nociceptive transmission. The purpose of the present review is to summarize the current knowledge of the structure of the pain system, including both the ascending and the descending components. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 11,126 |
Patterns of morphological variation within myelin internodes of normal peripheral nerve: quantitative analysis by confocal microscopy. | Stereological characteristics of the equine accessory nerve. | Remodeling of chromatin loops does not account for specification of replication origins during Xenopus development | eng_Latn | 11,127 |
Printed in Great Britain PRIMARY AFFERENT DEPOLARIZATION OF MYELINATED FIBRES IN THE JOINT AND INTEROSSEOUS NERVES OF THE CAT | Monosynaptic excitation of dorsal spinocerebellar tract neurones from low threshold joint afferents. | Brain Injury Does Not Alter the Intrinsic Differentiation Potential of Adult Neuroblasts | yue_Hant | 11,128 |
In spiders, retrograde cobalt staining was used to clarify the distribution and detailed innervation of the three types of proprioceptors in the tibio-metatarsal leg joint: internal joint receptors, lyriform slit sense organs, and cuticular spines and hairs. The axons of all these receptors run in just two lateral, ascending nerves, which had previously been associated only with the internal receptors. Each nerve contains several hundred axons ranging in diameter from 0.1 micron to ca. 10 micron. Each slit of the four tibial lyriform organs is innervated by two bipolar sensory neurons. The lateral nerves are entirely sensory and run just beneath the cuticle, a convenient site for electrophysiological recording. We demonstrate simultaneous nerve and muscle recordings from intact spiders; these, in combination with selective sensory ablations, show that a resistance reflex in the flexor metatarsi muscles is elicited by internal joint-receptor units. | Scanning white light interferometry and micro-force measurements were applied to analyse stimulus transformation in strain sensors in the spider exoskeleton. Two compound or 'lyriform' organs consisting of arrays of closely neighbouring, roughly parallel sensory slits of different lengths were examined. Forces applied to the exoskeleton entail strains in the cuticle, which compress and thereby stimulate the individual slits of the lyriform organs. (i) For the proprioreceptive lyriform organ HS-8 close to the distal joint of the tibia, the compression of the slits at the sensory threshold was as small as 1.4 nm and hardly more than 30 nm, depending on the slit in the array. The corresponding stimulus forces were as small as 0.01 mN. The linearity of the loading curve seems reasonable considering the sensor's relatively narrow biological intensity range of operation. The slits' mechanical sensitivity (slit compression/force) ranged from 106 down to 13 nm mN(-1), and gradually decreased with decreasing slit length. (ii) Remarkably, in the vibration-sensitive lyriform organ HS-10 on the metatarsus, the loading curve was exponential. The organ is thus adapted to the detection of a wide range of vibration amplitudes, as they are found under natural conditions. The mechanical sensitivities of the two slits examined in this organ in detail differed roughly threefold (522 and 195 nm mN(-1)) in the biologically most relevant range, again reflecting stimulus range fractionation among the slits composing the array. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 11,129 |
1. In the abdomen and thorax of some groups of Crustacea (Stomatopoda, Decapoda Macrura, and Anomura) ganglion cells have been found with ramifications into special muscle-fibres. It is assumed that these are organs for response to stimuli resulting from muscular activity and therefore the name ‘muscle receptor organs’ has been adopted for them. Each muscle receptor unit consists of ( a ) a thin muscle, ( b ) one ganglion cell connected with this muscle by means of numerous dendritic processes, and ( c ) various nerves supplying the muscle and entering into connexion with ganglion cells. This paper describes the results of a study of these organs in the abdomen of Homarus vulgaris and Palinurus vulgaris . 2. In each of the six abdominal segments of these animals there are two muscle receptor units on each side lying close to one another at the level of the superficial dorsal muscles. Their muscle components are quite distinct from the neighbouring muscles and preserve their individuality throughout their whole course and at their attachments. Moreover, the two muscles of the same side exhibit differences in their length, their attachments, and even their histological structure. Each muscle in about the middle of its length has a region made up of connective tissue fibres which may be regarded as an intercalated tendon. 3. Situated near to and in connexion with each of these muscle units is one large nerve-cell; there are, therefore, four such cells in each segment and a total of twenty-four in the abdomen. The cells are multipolar in shape with a variable number of short dendritic processes abundantly ramifying in the intercalated tendinous region of the muscle. The long processes, the axons, join the dorsal branch of the nerve supplying the extensor muscles and run in it towards the ganglionic cord. 4. In preparations made from embryonic lobsters it has been possible to establish that these axons bifurcate after entering the ganglionic cord, and the resulting branches run in opposite directions. Associating with similar fibres from other segments they form a tract situated in the nerve-cord near to its median line and running through all the ganglia of the abdominal and thoracic segments. 5. It has been found that in addition to the ganglion cells, at least three kinds of nerves take part in the innervation of the muscle receptors. They have been described under the names of: ( a ) motor nerves, ( b ) thick accessory nerve, and ( c ) thin accessory nerve. 6. Special means for protecting the muscle receptor organs are present. The nerve-cells are encapsuled and encircled by several layers of thin membranous tissue. The muscles are surrounded by connective tissue fibres and a special arrangement of these fibres supports the muscles in position. 7. As regards the function of these organs, the hypothesis is put forward that they might come into action during vigorous movements of the abdomen in the escape reaction of the animal. If this be so, they may perhaps convey inhibitory impulsesto the elements causing the rapid contractions of the flexor muscles. As these contractions are governed by the giant fibre system it might be expected that the neurons of the receptor organs enter into relation with some elements of that system. | Histological and electrophysiological studies of identified long hair sensilla (LHS) have provided information on primary afferent fibre pathways in the ventral nerve cord of the Indian black scorpion, Heterometrus fulvipes. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 11,130 |
Spinal nerves were transected at selected thoracic levels on the left side and the central cut end of the left major splanchnic nerve was exposed to horseradish peroxidase (HRP) in order to study the preganglionic sympathetic organization in the spinal cord of the cat. In three animals, a total of 4235 HRP labeled neurons were observed (uncorrected counts) in five regions: intermediolateral nucleus (IML) (82.8%), lateral funiculus (LF) (14.7%), intercalatus nucleus (IC) (2.1%), central autonomic (CA) (0.3%) and the anterior horn (AH) (0.1%). The neuronal distribution indicates that sympathetic preganglionic neurons in the thoracic spinal cord are segmentally organized. | The segmental organization of the thoracic sympathetic trunk and all its ramifications was studied in 6 human fetuses (16-22 weeks) by means of the acetylcholinesterase in toto staining method. Each trunk was divided into 12 sympathetic segments. A segment is defined as that part of the sympathetic trunk which is connected via its rami communicantes with one spinal nerve, without discriminating between grey and white rami. The diameter of the rami communicantes and their direction towards the spinal nerves are variable. The number of peripheral segmental ramifications of the trunk is much larger than assumed previously. Each thoracic sympathetic segment gives off at least 4-5 nerves. Three categories of nerves are discerned: (1) large splanchnic rootlets confined to the greater, lesser and least thoracic splanchnic nerves, (2) medium-sized splanchnic nerves directed towards thoracic viscera, some of which give off branches towards costovertebral joint plexuses and, described for the first time in man, (3) small nerves which ramify extensively and form nerve plexuses in the capsule of the costovertebral joints. The majority of the ramifications is formed by the nerves of the third category. The existence of Kuntz's nerve, connecting the 2nd intercostal nerve and 1st thoracic spinal nerve, is confirmed in four specimens. The nerve plexuses of the costovertebral joints receive a segmentally organized innervation: they receive their input from the neighbouring sympathetic segment and the one cranial to it. It is concluded that the thoracic sympathetic branches in man show a complex, segmentally organized pattern and may have a considerable component of somatosensory nerve fibers. The complex relationships must be taken into account in surgical sympathectomies. | It is proved, by using topological properties, that when a group automorphism of a locally compact totally disconnected group is ergodic under the Haar measure, the group is compact. The result is an answer for Halmos's question that has remained open for the totally disconnected case. | eng_Latn | 11,131 |
Tongue movements contribute to oral functions including swallowing, vocalizing, and breathing. Fine tongue movements are regulated through efferent and afferent connections between the cortex and tongue. It has been demonstrated that cortico-muscular coherence (CMC) is reflected at two frequency bands during isometric tongue protrusions: the beta (β) band at 15–35 Hz and the low-frequency band at 2–10 Hz. The CMC at the β band (β-CMC) reflects motor commands from the primary motor cortex (M1) to the tongue muscles through hypoglossal motoneuron pools. However, the generator mechanism of the CMC at the low-frequency band (low-CMC) remains unknown. Here, we evaluated the mechanism of low-CMC during isometric tongue protrusion using magnetoencephalography (MEG). Somatosensory evoked fields (SEFs) were also recorded following electrical tongue stimulation. Significant low-CMC and β-CMC were observed over both hemispheres for each side of the tongue. Time-domain analysis showed that the MEG signal followed the electromyography signal for low-CMC, which was contrary to the finding that the MEG signal preceded the electromyography signal for β-CMC. The mean conduction time from the tongue to the cortex was not significantly different between the low-CMC (mean, 80.9 ms) and SEFs (mean, 71.1 ms). The cortical sources of low-CMC were located significantly posterior (mean, 10.1 mm) to the sources of β-CMC in M1, but were in the same area as tongue SEFs in the primary somatosensory cortex (S1). These results reveal that the low-CMC may be driven by proprioceptive afferents from the tongue muscles to S1, and that the oscillatory interaction was derived from each side of the tongue to both hemispheres. Oscillatory proprioceptive feedback from the tongue muscles may aid in the coordination of sophisticated tongue movements in humans. | The proprioceptive innervation of the tounge has been investigated in the Cynamolgus monkey by silver impregnation methods following unilateral section of lingual, hypoglossal, and cervical nerves. Muscle spindles were constantly present in the intrinsic and extrinsic muscles. They varied greatly in number, averaged half the length of lumbrical spindles, and showed an unusual arrangement of chain fibre nuclei. Other, inconstant proprioceptors included tendon endings, Ruffini endings, Pacinian corpuscles, paciniform and lamellated endings. Topologically, the endings other than spindles were extra-muscular, so that the overall pattern of proprioceptive innervation resembled that of skeletal muscle in general. Lingual nerve section was without apparent effect on the proprioceptors. Section of the hypoglossal nerve at its point of entry into the tongue caused severe depletiion of ipsilateral proprioceptors and of fusimotor nerves. In the anterior tongue there was evidence of transmedian overlap by efferent and afferent axons contained in the hypoglossal nerve. Hypoglossal section at the skull base caused degeneration of fusimotor nerves but not of proprioceptors. Section of (a), the connexion of C2-C3 ventral rami with the hypoglossal, together with section of (b), the ramus descendens hypoglossi, coused depletion of lingual proprioceptors; again there was evidence of transmedian overlap. Procedures (a) or (b) alone had a lesser effect. It was concluded that lingual proprioceptive afferent fibres occupy the distal hypoglossal nerve, leaving it in the ramus descendens and in the C2-C3 connexion to enter the spinal cord via nerves C2 and C3. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 11,132 |
There is a canonical A n -fibration from a ( 2 n + 1 ) -dimensional smooth affine quadric Y n to an ( n + 1 ) -dimensional punctured affine space X n . For each rank r at least n , we construct a nontrivial algebraic vector bundle of rank r on X n with trivial pullback to Y n . Moreover, we construct continuous families of arbitrarily large dimensional pairwise non-isomorphic rank n bundles on X n with trivial pullbacks to Y n . | An electrically operable stimulator and method for the control of pain or for other purposes through muscle and/or nerve stimulation by application of electrical pulses to the body of an animal, such as a human being. The stimulator generally comprises an internal power supply which may be rechargeable and which operates in conjunction with a pulse generator and an output amplifier. The pulse generator includes a unijunction transistor multivibrator and which is uniquely designed to achieve low current drain. Pulse interval and pulse width and pulse amplitude are controlled through separate and non-interacting controls. The output amplifier provides an output which is an excellent impedance match to the animal body for controlled stimulation. The output amplifier is uniquely designed to draw current only in proporton to the amount required, so that the entire apparatus is highly efficient. | not available DOI: http://dx.doi.org/10.3329/pulse.v5i2.20263 Pulse Vol.5 July 2011 p.31-40 | eng_Latn | 11,133 |
Mechanoreceptive neurons with or without taste responsiveness were recorded in the cortical taste area (CTA) of rats every 50 or 100 µm along an electrode track made as perpendicular to the surface as possible. Three groups of mechanoreceptive neurons were recognized based on the adequate stimulus, i.e., low-threshold mechanoreceptive (n=16), nociceptive-specific (n=48), and wide-dynamic range neurons (n=392). Except for nine neurons, almost all had receptive fields (RFs) in the oral cavity (n=447). They were categorized into three RF types: those with RFs only in the oral cavity (OC type; n=23), those with RFs both in the oral cavity and on the lip (OL type; n=44) and those with RFs in the oral cavity and on the external surface of the body (WB type; n=380), e.g., tail. Neurons with inhibitory RFs were often located in the infragranular layers. Several neurons with the same receptive features were sequentially recorded along the track, suggesting the presence of columnar organization. The diameter of the possible functional column was the largest (mean 113.85 µm) for WB type neurons, but smaller in the other two types (mean 85 µm for the OC type and 62.5 µm for the OL type). Neurons were segregated according to the adequate stimulus within the column for WB type neurons. Taste-responsive mechanoreceptive neurons (n=33) were recorded at 15 tracks, and two taste neurons were sequentially recorded in five cases, in three of which two successive neurons sharing the best stimulus were recorded. Taste neurons are possibly arranged in a column with a very small diameter within the large column of mechanoreceptive neurons. | The functional organization of the insular cortex was studied by recording neuronal responses to visceral sensory stimuli. Horseradish peroxidase (HRP) was then iontophoresed at the recording sites to identify afferents from the ventrobasal thalamus to specific visceroceptive sites in the insular cortex. The relationship of the ventrobasal thalamus to the insular cortex and to brainstem relay nuclei for the ascending visceral projections was then examined by using the axonal transport of HRP, wheat germ agglutinin conjugated to HRP (WGA-HRP), and fluorescent dyes. Of a total of 55 neurons that were tested for responses to visceral sensory stimuli, 33 units responded to atleast one visceral sensory modality: 6 received gastric mechanoreceptor input, 8 responded to taste inputs, 13 were activated by arterial chemoreceptors and/or showed respiratory related activity, and 6 responded to cardiovascular baroreceptor stimulation. On the basis of its cytoarchitecture and connections with the thalamus, the insular cortex was divided into a dorsal granular area, an intermediate dysgranular region, and a ventral agranular strip. Taste-responsive neurons were located anteriorly, primarily in the dysgranular region, whereas unit responses to general visceral modalities were distributed dorsally and posteriorly in the granular insular cortex. Gastric mechanoreceptor-responsive units were situated more dorsally and anteriorly in the granular insular cortex, while cardiopulmonary inputs were located more ventrally and posteriorly. Injections of HRP into the gustatory insular cortex resulted in retrograde labeling of neurons in the parvicellular part of the ventroposterior medial thalamic nucleus (VPMpc). Injections into the general visceral insular cortex retrogradely labeled neurons lateral to VPMpc in the ventroposterior lateral parvicellular thalamic nucleus (VPLpc). Injections of HRP, WGA-HRP, and fluorescent dyes into VPMpc and VPLpc verified that their projection to the insular cortex is topographically organized. In the same experiments, retrogradely labeled neurons in the parabrachial nucleus identified the likely subnuclei within this nucleus for relay of visceral sensory information to the thalamus. Injections of WGA-HRP into the parabrachial nucleus demonstrated that its projection to the ventrobasal thalamus is also topographically organized. These results demonstrate the relationship of general visceral and special visceral (taste) representations in the insular cortex. The ascending pathway for visceral sensory information appears to be viscerotopically organized at all levels of the neuraxis, including the insular cortex. | An electrically large resonant cavity (ELRC) operated at the TM100 dominant mode with unconstrained physical size is proposed in this letter. The rectangular cavity is filled partially by ε-negative metamaterial and μ-negative metamaterial. Modal equation for the dominant mode TM100 of the ELRC is deduced based on the cavity model theory. Numerical results indicate that the resonant frequency can be increased in a much degree in comparison to the cavity composed of normal material. Finally, electric field distributions of the proposed cavity are plotted, and the quality factor is calculated to verify the resonant property of the ELRC, which shows it is a good candidate for the electrically large antenna applications. | eng_Latn | 11,134 |
Analysis of the processes of summation of postsynaptic potentials on the membrane of motoneurons upon realization of the stretch reflex | The time courses of excitatory and inhibitory synaptic actions. | EXO0748−676 Rules out Soft Equations of State for Neutron Star Matter | eng_Latn | 11,135 |
Joint position and velocity derived from muscle spindle output: a neural network approach | Somatosensory cortical mechanisms of feature detection in tactile and kinesthetic discrimination | SNARE Function Is Not Involved in Early Endosome Docking | eng_Latn | 11,136 |
Synaptic plasticity and intrinsic changes in neuronal excitability are two mechanisms for Pavlovian conditioning. Pavlovian conditioning of Hermissenda produces synaptic facilitation of monosynaptic medial B-medial A IPSPs and intrinsic changes in excitability of type A and B cells in isolated and intact sensory neurons of the conditioned stimulus (CS) pathway. Recently two types of interneurons that receive either excitatory or inhibitory monosynaptic or polysynaptic input from photoreceptors have been identified. On the basis of morphological and electrophysiological criteria, the interneurons have been classified as type I(e), I(i) (direct), and type II(e), II(i) (indirect). We have now examined synaptic facilitation of monosynaptic PSPs in type I(e) and I(i) interneurons after conditioning and pseudorandom control procedures. Here we report that CS-elicited spike activity is increased in type I(e) interneurons and decreased in type I(i) interneurons of conditioned animals relative to their respective baseline activity and pseudorandom control groups. Classical conditioning resulted in synaptic facilitation of type I(e) and I(i) monosynaptic PSPs elicited by lateral B spikes and enhancement of the amplitude of complex PSPs elicited by the CS. These results provide additional sites of plasticity in the neural circuit involved with the expression of learned behavior produced by Pavlovian conditioning of Hermissenda. | A Pavlovian-conditioning procedure may produce modifications in multiple behavioral responses. As an example, conditioning may result in the elicitation of a specific somatomotor conditioned response (CR) and, in addition, other motor and visceral CRs. In the mollusk Hermissenda conditioning produces two conditioned responses: foot-shortening and decreased locomotion. The neural circuitry supporting ciliary locomotion is well characterized, although the neural circuit underlying foot-shortening is poorly understood. Here we describe efferent neurons in the pedal ganglion that produce contraction or extension of specific regions of the foot in semi-intact preparations. Synaptic connections between polysensory type Ib and type Is interneurons and identified foot contractile efferent neurons were examined. Type Ib and type Is interneurons receive synaptic input from the visual, graviceptive, and somatosensory systems. Depolarization of type Ib interneurons evoked spikes in identified tail and lateral foot co... | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 11,137 |
We describe methods of fine scale chemical and topographical patterning of silicon substrates and the selected attachment and growth of central nervous system cells in culture. We have used lithography and microcontact printing to pattern surfaces with self-assembled monolayers and proteins. Chemical patterns can be created that localize and guide the growth of cells on the surfaces. Self-assembled surface texturing with structures at the tens of nanometers scale and lithographic based methods at the micrometer scale have been used to produce a variety of surface topographical features. These experiments suggest that surface texture at the scale of tens of nanometers to micrometers can influence the attachment of these cells to a surface and can be used as a mechanism of isolating cells to a particular area on a silicon substrate. | Advances in neuroscience and bioengineering have led to a nascent discipline known as neural engineering, whose activity ranges from neurally inspired computer algorithms to brain and peripheral nerve prostheses to imaging of functional brain activity. This paper describes progress in a neural engineering research area in which the goal is to learn how to construct neuronal networks de novo with individual living nerve cells as the fundamental circuit elements. The effort is in part microlithography, applicable because the sizes of neurons and transistors are the same. In part it is surface chemistry, as it is necessary to couple diverse chemistries and molecules to surfaces in order to control neuron attachment and growth. It is in part electrical engineering, as the principal I/O devices are microelectrode arrays capable of recording or stimulating at dozens and in the future hundreds of sites. Modern data acquisition and real-time analysis are also necessary to store, recognize, and analyze the multichannel data. Overwhelmingly, however, the problems are ones of neuroscience and cell biology, of controlling the many factors that influence cell attachment, growth, and interactions with other cells. Despite this seemingly unending list of prerequisites, substantial progress is being made to the point where we can seriously begin to ask a variety of scientifically relevant questions. One of these is to ask whether or not these biological neuronal networks behave at all like their computational namesakes. | Blunt trauma abdomen rarely leads to gastrointestinal injury in children and isolated gastric rupture is even rarer presentation. We are reporting a case of isolated gastric rupture after fall from height in a three year old male child. | eng_Latn | 11,138 |
In what type of cell would you find an axon and dendrites? | The Neuron The Neuron Ukrainian translation by Valerie Bastiaan: Нейрон Neurons It is clear that most of what we think of as our mental life involves the activities of the nervous system, especially the brain. This nervous system is composed of billions of cells, the most essential being the nerve cells or neurons. There are estimated to be as many as 100 billion neurons in our nervous system! spinal cord neuron A typical neuron has all the parts that any cell would have, and a few specialized structures that set it apart. The main portion of the cell is called the soma or cell body. It contains the nucleus, which in turn contains the genetic material in the form of chromosomes. Neurons have a large number of extensions called dendrites. They often look likes branches or spikes extending out from the cell body. It is primarily the surfaces of the dendrites that receive chemical messages from other neurons. One extension is different from all the others, and is called the axon. Although in some neurons, it is hard to distinguish from the dendrites, in others it is easily distinguished by its length. The purpose of the axon is to transmit an electro-chemical signal to other neurons, sometimes over a considerable distance. In the neurons that make up the nerves running from the spinal cord to your toes, the axons can be as long as three feet! Longer axons are usually covered with a myelin sheath, a series of fatty cells which have wrapped around an axon many times. These make the axon look like a necklace of sausage-shaped beads. They serve a similar function as the insulation around electrical wire. At the very end of the axon is the axon ending, which goes by a variety of names such as the bouton, the synaptic knob, the axon foot, and so on (I do not know why no one has settled on a consistent term!). It is there that the electro-chemical signal that has travelled the length of the axon is converted into a chemical message that travels to the next neuron. axon endings Between the axon ending and the dendrite of the next neuron is a very tiny gap called the synapse (or synaptic gap, or synaptic cleft), which we will discuss in a little bit. For every neuron, there are between 1000 and 10,000 synapses. The action potential When chemicals contact the surface of a neuron, they change the balance of ions (electrically charged atoms) between the inside and outside of the cell membrane. When this change reaches a threshold level, this effect runs across the cell's membrane to the axon. When it reaches the axon, it initiates the action potential, which is a rapidly moving exchange of ions. The surface of the axon contains hundreds of thousands of miniscule mechanisms called ion channels. When the charge enters the axon, the ion channels at the base of the axon allow positively charged ions to enter the axon, changing the electrical balance between inside and outside. This causes the next group of ion channels to do the same, while other channels return positive ions to the outside, and so on all the way down the axon. In this little diagram, the red represents the positive ions going into the axon, while the orange represents positive ions going out. The action potential travels at a rate of 1.2 to 250 miles per hour! This is, of course, over-simplified, but enough for our purposes. But if you are interested in a little more detail, click here! The synapse When the action potential reaches the axon ending, it causes tiny bubbles of chemicals called vesicles to release their contents into the synaptic gap. These chemicals are called neurotransmitters. These sail across the gap to the next neuron, where they find special places on the cell membrane of the next neuron called receptor sites. The neurotransmitter acts like a little key, and the receptor site like a little lock. When they meet, they open a passage way for ions, which then change the balance of ions on the outside and the inside of the next neuron. And the whole process starts all over again. While most neurotransmitters are excitatory -- i.e | European bison | mammal | Britannica.com European bison THIS IS A DIRECTORY PAGE. Britannica does not currently have an article on this topic. Alternative Titles: Bison bonasus, wisent Wisent (Bison bonasus). A small group of European bison (Bison bonasus) grazing near the mountains. Encyclopædia Britannica, Inc. European bison (Bison bonasus), also called wisent, in Prioksko-Terrasny Nature Reserve, Russia. © joppo/Fotolia University College Cork, Ireland (A Britannica Publishing Partner ) Learn about this topic in these articles: in Belovezhskaya Forest ...than 6 feet [2 metres]) and fauna (including elk, deer, lynx, and wild boar) from both western and eastern Europe. Hunted into extinction in the wild after World War I, the European bison, or wisent, was reintroduced to the Belovezhskaya with zoo-bred animals. The forest remains the European bison’s most notable home, though the animals are now also found again in other parts of Europe,... in bison The European bison, or wisent, differs from the American bison in several respects. It lives in woodlands and is slightly larger and longer-legged than the American bison but is less heavily built. The European bison’s range originally extended eastward across Europe to the Volga River and the Caucasus Mountains. It became extinct in the wild after World War I, but herds built from zoo-bred... in Belarus: Plant and animal life ...both sides of the frontier. The rich forest vegetation that once covered much of Europe survives here, dominated by trees that have grown to exceptional heights. The forest is the major home of the European bison, or wisent, which had become extinct in the wild following World War I but was reintroduced through captive breeding. Elk, deer, and boars also are found there and in other forests of... | eng_Latn | 11,139 |
What is part of the dorsal body cavity? | Is the dorsal cavity in the endocrine system? | Is the dorsal cavity in the endocrine system? | eng_Latn | 11,140 |
How does the schwann cell form the myelin sheath and the neurilemma? | Desribe how schwann cells form the myelin sheath and the neurilemma encasing the nerve processes? | Desribe how schwann cells form the myelin sheath and the neurilemma encasing the nerve processes? | eng_Latn | 11,141 |
Which is the largest nerve in the human body? | Sciatic Nerve - Anatomy Pictures and Information Home > Nervous System > Nerves of the Leg and Foot > Sciatic Nerve Sciatic Nerve The sciatic nerve is the largest and longest spinal nerve in the human body. Extending from the lumbar and sacral plexuses in the lower back, the sciatic nerve runs through the buttocks and into the thighs. It delivers nerve signals to and from the muscles and skin of the thighs, lower legs and feet. The sciatic nerve forms from the merger of the fourth and fifth lumbar nerves with the first, second, and third sacral nerves.... Move up/down/left/right: Click compass arrows Rotate image: Click and drag in any direction, anywhere in the frame Identify objects: Click on them in the image 2D Interactive 3D Rotate & Zoom Change Anatomical System Change View Angle Full Sciatic Nerve Description [Continued from above] . . . From the lower back, the sciatic nerve runs inferiorly into the gluteal region and into the posterior of the femoral region of the leg. Smaller individual nerves branch off from the sciatic nerve to innervate our thigh muscles and skin. At the inferior end of the femoral region, the sciatic nerve branches off into the tibial and common fibular nerves, which continue carrying nerve signals into the lower legs and feet. Histology Like all spinal nerves, our sciatic nerve contains many individual neurons that run along the length of the nerve like strands of thread in a thick yarn. Each neuron is wrapped in a thin layer of connective tissue called the endoneurium. The neurons are bundled together into groups called fascicles, which are further wrapped by connective tissue called the perineurium. Many fascicles are bundled together to form the entire sciatic nerve, which is further wrapped by a sheet of connective tissue known as the epineurium. Blood vessels run between the fascicles to provide oxygen and nutrients to support the nerve cells and remove waste products. Physiology The sciatic nerve innervates many of the posterior muscles of the thighs directly and innervates the muscles of the lower legs and feet indirectly through its branches. Sensory neurons carrying signals from the skin of the hip and thigh also run through the sciatic nerve toward the spinal cord. Prepared by Tim Taylor, Anatomy and Physiology Instructor | The Other National Christmas Tree The Other National Christmas Tree The official Christmas tree of the wild, wild west General Grant tree with a cover of snow and a Christmas wreath, Photo By: Alexandra Picavet By Christina Scannapiego Recreation.gov We Americans have the National Christmas Tree Lighting in Washington, DC, to ring us into the holiday season year after year—but few people know that the Wild West also celebrates its own National Christmas tree, a giant sequoia and the second largest tree in the world, in the General Grant Grove section of Kings Canyon National Park in California. As you might have guessed, the grove and the tree were both named after Union Army general and 18th president of the United States, Ulysses S. Grant, but it was in 1926 that President Calvin Coolidge finally ordained the majestic tree the "Nation’s Christmas Tree". The idea was inspired by a little girl who had imagined the giant as a Christmas tree and shared the thought with Sanger, California resident, Charles E. Lee. From then on, Lee began organizing yearly Christmas programs around the tree, in the enchanted grove of sequoias, until the event became an annual ceremony. And to this day, every Christmas, many campers, hikers and nature lovers come to honor this venerable pillar of the American Christmas spirit, and the Sanger Chamber of Commerce continues to sponsor the annual holiday, "Trek to the Tree" on the second Sunday of December each year. You can visit the General Grant tree almost any time of year on a short half-mile loop trail. The trailhead is one mile beyond the Grant Grove Visitor Center on the west side of the road. If you're going overnight, make reservations for Lodgepole Campground . You can start making reservations for July as early as January, but be sure and check back in the spring to find out if snow melt allows the campground to open earlier. | eng_Latn | 11,142 |
In which part of the body is the 'Sural Nerve'? | Sural Nerve Entrapment Explained | | Chronic Body Pain Foot Pain Sural Nerve Entrapment Explained Before we can discuss what sural nerve entrapment is, you really should know what the sural nerve is and what it does. The sural nerve is also referred to as the short saphenous nerve. It is the sensory nerve located in the lower leg. This nerve lies very close to the short saphenous vein, which is a major vein located in the calf. The sural nerve can begin from just behind the knee to just below the ankle. This particular nerve is often used for nerve grafts and biopsies. The sural nerve begins and the juncture of the lateral and medial sural cutaneous nerves. In most individuals, this typically occurs very low in the leg- even at or below the ankle in some cases. On the other hand, in a few individuals, the sural nerve can begin as high as behind the knee. , in some individuals, the sural nerve is actually simply a continuation of the medial sural cutaneous nerve. This nerve travels down an individual’s calf just below the surface of the skin, passing close to the Achilles tendon and then ending in the space between the heel and the bony bump on the outside of the ankle, known as the lateral malleolus. It actually continues into the foot, reaching the little toe- but once it passes the ankle, it is given a different name- the lateral dorsal cutaneous nerve. The sural nerve conveys sensory information regarding the lower calf and outer foot to the brain- damage to this nerve can result in extreme pain in the leg or foot. However, if damage does occur, it can be treated by removing part of the nerve. Of course, removal of a portion of the nerve can result in numbness in the ankle and side of the foot- but the nearby nerves will grow in to compensate, which restores most of the feeling to the area. Due to the fact that the sural nerve is just below the skin and it’s basically not important to essential bodily functioning, it is often used when a nerve biopsy is necessary. To perform a biopsy, the surgeon will inject a local anesthetic and then, using the short saphenous vein to guide him/her, will locate the sural nerve and then remove a piece about an inch long. The wound will then be stitched closed and then covered with gauze moistened with saline. The sample will then be placed under a microscope and examined for evidence of nerve disorders. Additionally, this nerve is often chosen to be used in nerve grafts. This is where a piece of the nerve will be taken out and transplanted into an area where nerves have been damaged. The donor piece will be spliced with the existing nerve to restore muscle functioning and sensation. This procedure is commonly used to restore the feeling in damaged limbs. The sural nerve is being transplanted more often into the pelvic area after prostate surgery to restore any lost sexual functioning. Sural Nerve Neuropathy Though the sural nerve is not necessarily essential to bodily functioning, it is still a nerve, and just like other bodily tissues, can experience disease and/or trauma. The sural nerve is a peripheral nerve, meaning that it serves to communicate with the brain and spinal cord. Sural nerve damage is a subtype of peripheral neuropathy. There are some important characteristics of sural nerve damage related to the functioning and the anatomy of the involved structures. Types of Neurons and Related Anatomy Nerve cells, also referred to as neurons are divided into three major categories: Sensory Motor Interneurons The sensory neurons pick up the sensory signals and then take them to the spinal cord and the brain. On the other hand, the motor neurons take commands from the spinal cord and the brain and carry them to the muscles or glands to tell them what to do. However, no matter what their primary function, all neurons have the same specific structural components: Cell body Axon Dendrites The cell body holds the nucleus and is the center of the metabolism of the neuron. The axon is a very long fiber of nerve that carries the signals away from the cell body. The dendrites are short pro | Carry On... Up The Khyber - Film - British Comedy Guide Carry On... Up The Khyber Carry On... Up The Khyber Like this film Carry On... Up The Khyber Like this film Trivia Carry On... Up The Khyber Sir Sidney Ruff-Diamond is in charge of the motley kilted crew of the Third Foot and Mouth regiment at a British outpost in the Khyber Pass Genre 1969 Starring Peter Rogers It is 1895 and the British Governor in India's Kalabar province, Sir Sidney Ruff-Diamond, enjoys his laid-back, luxurious colonial lifestyle - but is all too aware of the feelings of certain natives, particularly the Khasi of Kalabar, northern India's most powerful Raja. Amongst Ruff-Diamond's responsibilities are the 3rd Foot and Mouth Regiment, known by the natives as the Devils in Skirts owing to their kilt-wearing, who guard the vital route into India at the Khyber Pass. The Khasi is far from content with the status quo and wants the British dead. However, his troops fear what the imperial forces may or may not have under their "skirts" - it gets awfully windy up the pass, and any man who can go without protection should be feared! When one of the soldiers is discovered to be wearing woollen underpants under his skirt, however, the Khasi is delighted. It's just the proof he needs to inspire his own men, not to mention the local populace, to drive the British out of India once and for all. Sir Sidney, however, is not about to let that happen without a fight... | eng_Latn | 11,143 |
What is the longest nerve in the human body? | Sciatic Nerve - Anatomy Pictures and Information Home > Nervous System > Nerves of the Leg and Foot > Sciatic Nerve Sciatic Nerve The sciatic nerve is the largest and longest spinal nerve in the human body. Extending from the lumbar and sacral plexuses in the lower back, the sciatic nerve runs through the buttocks and into the thighs. It delivers nerve signals to and from the muscles and skin of the thighs, lower legs and feet. The sciatic nerve forms from the merger of the fourth and fifth lumbar nerves with the first, second, and third sacral nerves.... Move up/down/left/right: Click compass arrows Rotate image: Click and drag in any direction, anywhere in the frame Identify objects: Click on them in the image 2D Interactive 3D Rotate & Zoom Change Anatomical System Change View Angle Full Sciatic Nerve Description [Continued from above] . . . From the lower back, the sciatic nerve runs inferiorly into the gluteal region and into the posterior of the femoral region of the leg. Smaller individual nerves branch off from the sciatic nerve to innervate our thigh muscles and skin. At the inferior end of the femoral region, the sciatic nerve branches off into the tibial and common fibular nerves, which continue carrying nerve signals into the lower legs and feet. Histology Like all spinal nerves, our sciatic nerve contains many individual neurons that run along the length of the nerve like strands of thread in a thick yarn. Each neuron is wrapped in a thin layer of connective tissue called the endoneurium. The neurons are bundled together into groups called fascicles, which are further wrapped by connective tissue called the perineurium. Many fascicles are bundled together to form the entire sciatic nerve, which is further wrapped by a sheet of connective tissue known as the epineurium. Blood vessels run between the fascicles to provide oxygen and nutrients to support the nerve cells and remove waste products. Physiology The sciatic nerve innervates many of the posterior muscles of the thighs directly and innervates the muscles of the lower legs and feet indirectly through its branches. Sensory neurons carrying signals from the skin of the hip and thigh also run through the sciatic nerve toward the spinal cord. Prepared by Tim Taylor, Anatomy and Physiology Instructor | Which 100-mile long waterway links the Mediterranean and the RedSea? View the step-by-step solution to: Which 100-mile long waterway links the Mediterranean and the RedSea? This question was answered on Jun 08, 2016. View the Answer Which 100-mile long waterway links the Mediterranean and the RedSea? ChristopherLane posted a question · Jun 08, 2016 at 1:45am Top Answer Here's the explanation you needed for... View the full answer {[ getNetScore(29990764) ]} leonardkabib answered the question · Jun 08, 2016 at 1:46am Other Answers Here's the explanation you needed for... View the full answer {[ getNetScore(29994732) ]} The Suez canal which connects the... View the full answer {[ getNetScore(30000863) ]} Search for Other Related Study Materials Recently Asked Questions Need a World History tutor? mathtutor1983 2 World History experts found online! Average reply time is less than an hour Get Homework Help Why Join Course Hero? Course Hero has all the homework and study help you need to succeed! We’ve got course-specific notes, study guides, and practice tests along with expert tutors and customizable flashcards—available anywhere, anytime. - - Study Documents Find the best study resources around, tagged to your specific courses. Share your own to gain free Course Hero access or to earn money with our Marketplace. - Question & Answers Get one-on-one homework help from our expert tutors—available online 24/7. Ask your own questions or browse existing Q&A threads. Satisfaction guaranteed! - Flashcards Browse existing sets or create your own using our digital flashcard system. A simple yet effective studying tool to help you earn the grade that you want! | eng_Latn | 11,144 |
Cranial nerves emerge directly from which organ in the human body? | SEER Training:The Peripheral Nervous System Updates The Peripheral Nervous System The peripheral nervous system consists of the nerves that branch out from the brain and spinal cord. These nerves form the communication network between the CNS and the body parts. The peripheral nervous system is further subdivided into the somatic nervous system and the autonomic nervous system. The somatic nervous system consists of nerves that go to the skin and muscles and is involved in conscious activities. The autonomic nervous system consists of nerves that connect the CNS to the visceral organs such as the heart, stomach, and intestines. It mediates unconscious activities. Structure of a Nerve A nerve contains bundles of nerve fibers, either axons or dendrites, surrounded by connective tissue. Sensory nerves contain only afferent fibers, long dendrites of sensory neurons. Motor nerves have only efferent fibers, long axons of motor neurons. Mixed nerves contain both types of fibers. A connective tissue sheath called the epineurium surrounds each nerve. Each bundle of nerve fibers is called a fasciculus and is surrounded by a layer of connective tissue called the perineurium. Within the fasciculus, each individual nerve fiber, with its myelin and neurilemma, is surrounded by connective tissue called the endoneurium. A nerve may also have blood vessels enclosed in its connective tissue wrappings. Cranial Nerves Twelve pairs of cranial nerves emerge from the inferior surface of the brain. All of these nerves, except the vagus nerve , pass through foramina of the skull to innervate structures in the head, neck, and facial region. The cranial nerves are designated both by name and by Roman numerals, according to the order in which they appear on the inferior surface of the brain. Most of the nerves have both sensory and motor components. Three of the nerves are associated with the special senses of smell, vision, hearing, and equilibrium and have only sensory fibers. Five other nerves are primarily motor in function but do have some sensory fibers for proprioception. The remaining four nerves consist of significant amounts of both sensory and motor fibers. Acoustic neuromas are benign fibrous growths that arise from the balance nerve, also called the eighth cranial nerve or vestibulocochlear nerve. These tumors are non-malignant, meaning that they do not spread or metastasize to other parts of the body. The location of these tumors is deep inside the skull, adjacent to vital brain centers in the brain stem. As the tumors enlarge, they involve surrounding structures which have to do with vital functions. In the majority of cases, these tumors grow slowly over a period of years. In other cases, the growth rate is more rapid and patients develop symptoms at a faster pace. Usually, the symptoms are mild and many patients are not diagnosed until some time after their tumor has developed. Many patients also exhibit no tumor growth over a number of years when followed by yearly MRI scans. Spinal Nerves Thirty-one pairs of spinal nerves emerge laterally from the spinal cord. Each pair of nerves corresponds to a segment of the cord and they are named accordingly. This means there are 8 cervical nerves, 12 thoracic nerves, 5 lumbar nerves, 5 sacral nerves, and 1 coccygeal nerve. Each spinal nerve is connected to the spinal cord by a dorsal root and a ventral root. The cell bodies of the sensory neurons are in the dorsal root ganglion, but the motor neuron cell bodies are in the gray matter. The two roots join to form the spinal nerve just before the nerve leaves the vertebral column. Because all spinal nerves have both sensory and motor components, they are all mixed nerves. Autonomic Nervous System The autonomic nervous system is a visceral efferent system, which means it sends motor impulses to the visceral organs. It functions automatically and continuously, without conscious effort, to innervate smooth muscle, cardiac muscle, and glands. It is concerned with heart rate, breathing rate, blood pressure, body temperature, and other visceral acti | Dr. Finlay's Casebook: Amazon.co.uk: A.J. Cronin: 9781841588544: Books Dr. Finlay's Casebook Customers Who Bought This Item Also Bought Page 1 of 1 Start over Page 1 of 1 This shopping feature will continue to load items. In order to navigate out of this carousel please use your heading shortcut key to navigate to the next or previous heading. Enter your mobile number or email address below and we'll send you a link to download the free Kindle App. Then you can start reading Kindle books on your smartphone, tablet, or computer - no Kindle device required. Apple To get the free app, enter your mobile phone number. or Don't have a Kindle? Get your Kindle here , or download a FREE Kindle Reading App . Product details Publisher: Birlinn Ltd; Omnibus ed edition (6 Mar. 2014) Language: English Product Dimensions: 12.7 x 2 x 20.3 cm Average Customer Review: Product Description About the Author Archibald Joseph Cronin, born in 1896, was a novelist, dramatist and writer of non-fiction who was one of the most renowned storytellers of the twentieth century. His best-known works are The Stars Look Down, The Citadel, The Keys of the Kingdom and The Green Years, all of which were adapted to film. He served as a Royal Navy surgeon during the First World War before graduating from medical school. During an enforced holiday from his medical practice due to ill health he composed his first novel, Hatter's Castle, with which he enjoyed immense success and which launched his career as a prolific author; he never returned to practicing medicine. He died on 6 January 1981 (aged 84) in Montreux, Switzerland. What Other Items Do Customers Buy After Viewing This Item? | eng_Latn | 11,145 |
What particular muscles and nerves control the heart rate? | Which nerve speeds up heart rate during stress? | Why does the heart rate decrease after vagus nerve stimulation? | eng_Latn | 11,146 |
What provides the main receptive surface for neurons? | What does the cytoplasmic extension at the neuron cell body provide? | What happens to neurons that are not taken up by the receptors? | eng_Latn | 11,147 |
What is the path a nerve impulse travels within a single neuron? | What is the path an impulse travels? | What path does a nerve impulse travel within a single neuron? | eng_Latn | 11,148 |
What are nerve cells that carry messages throughout the body? | Nerve cells that carry messages throughout the whole human body? | Nerve cells that carry messages throughout the whole human body? | eng_Latn | 11,149 |
How the circulatory system works together with other system? | How does the digestive systme work with other systems? | Does the nervous system work with circulatory system? | eng_Latn | 11,150 |
What effect does parasympathetic nervous system have on the heart contractions? | How do the sympathetic and parasympathetic nervous system work togerther to regulat heart rate? | Why do pigs not have inguinal hernias? | eng_Latn | 11,151 |
What nerves are involved in bell's palsy? | What is bell-palsy? | Why do pigs not have inguinal hernias? | eng_Latn | 11,152 |
What other cells does the nerve cells depend on? | How are muscle and nerve cells different? | How do they depend on each other? | eng_Latn | 11,153 |
Synaptic vesicles in the axon reminal of a motor neuron contain what neurotransmitter? | Synaptic vesicles in the axon terminal of a motor neuron opens what type of ion channel? | Why do venus and mercury not have moons? | eng_Latn | 11,154 |
Does the neurons conduct? | The speed at which a neuron sends its message along the axon is faster if the? | Why is a conductor a conductor? | eng_Latn | 11,155 |
What neuron that move impulses from the brain? | True or falseA neuron transfers information in the form of an electrical impulse? | Why don't snow leopards migrate? | eng_Latn | 11,156 |
What are numerous endings of each motor neuron? | What are the axon of each motor neuron's numerous endings? | What is the motor end plate part of? | eng_Latn | 11,157 |
Does a peripheal nerve pass from the spinal cord into the limbs? | Does a peripheral nerve pass from the spinal sord into the limbs? | Does a peripheral nerve pass from the spinal sord into the limbs? | eng_Latn | 11,158 |
Which cranial nerve influenes equilibrium? | What carnial nerve is responsible for equilibrium? | Individual Americans have no impact on the economy? | eng_Latn | 11,159 |
Why is human body considered as the most complex and most well coordinated body system? | Why is nervous system considered the most complex of the system of the body? | Why is nervous system considered the most complex of the system of the body? | eng_Latn | 11,160 |
What is impulses of nerves? | What constitutes a nerve impulse? | What is ture about the regarding nerve impulses? | eng_Latn | 11,161 |
What is the mian organ of the nervous system? | What is the main organs od the nervous system? | What is the largest vien in the human body? | eng_Latn | 11,162 |
Which cell type is responsible for the transmission of electrochemical impulses? | Does glia cells trasmit electrochemical impulses? | Does glia cells trasmit electrochemical impulses? | eng_Latn | 11,163 |
What part of the neuron carries the message to another neuron? | What recives messages from other neurons and sends to the cell body? | Why won't neon argon kryton xeon and radon combine with other elements? | eng_Latn | 11,164 |
Nervous system and cardiovascular how do they work together? | Does the nervous system work with circulatory system? | Does the nervous system work with circulatory system? | eng_Latn | 11,165 |
How information passes through the hormonal system? | What path does the stimulus travel through the nervous system? | Why do venus and mercury not have moons? | eng_Latn | 11,166 |
Branches out to form nerver fibers? | What branches out from nerve fibers? | What branches out to from nerve fibers? | eng_Latn | 11,167 |
Part of nerve that receivesnervous impulse? | What is ture about the regarding nerve impulses? | Is water a nonrenubel rescorce? | eng_Latn | 11,168 |
What anatomical charachteristic determines whether the particular neuron is classified as unipolar bipolar or multipolar? | What anatomical characteristics detrrmines whethr a particular neuron is classified as unipolarbiopolar or mulitpolar? | What anatomical characteristics detrrmines whethr a particular neuron is classified as unipolarbiopolar or mulitpolar? | eng_Latn | 11,169 |
Is the vagus nerves carry nerve impulses that decrease the heart rate? | Why does the heart rate decrease after vagus nerve stimulation? | Why does the heart rate decrease after vagus nerve stimulation? | eng_Latn | 11,170 |
What fiber carries impulses away from the cell body of the neuron? | What cell transmitts impulses throughout the body? | Why do pigs not have inguinal hernias? | eng_Latn | 11,171 |
In vertebrates , acetylcholine is the neurotransmitter used at the neuromuscular junction , where signals are transmitted between neurons from the central nervous systems to muscle fibres . | In vertebrates , acetylcholine is the neurotransmitter used at the neuromuscular junction , where signals are transmitted between neurons from the central nervous system to muscle fibres . | The ` crossing ' or exchanging of books may take many different forms , including wild releasing books in public , direct swaps with other members of the website , or `` book rings '' in which books travel in a set order to people who want to read that book . | eng_Latn | 11,172 |
The ampullae of Lorenzini are the electroreceptor organs . | In them are which are nerve receptors called the ampullae of Lorenzini . | Some ornithopods and cerapods had thin cartilaginous plates along the outside of the ribs . In some cases , these plates mineralized and so were fossilized . | eng_Latn | 11,173 |
What are some of the cranial nerves? What functions do they have? | What are the cranial nerves? | What is the constitutional definition of a 'natural' born citizen? | eng_Latn | 11,174 |
Even a shark's electrical 'sixth sense' may be tuned to attack | Credit: CC0 Public Domain Imagine having superhuman hearing. You're at a noisy, cocktail party and yet your ears can detect normally inaudible sounds made by your friends' muscles as they lean in to dish the latest gossip. But, unlike normal hearing, each of these sounds causes your ears to react in the same way. There is no difference between the quietest and loudest movements. To your superhuman ears, they all sound loud, like honking horns. According to a study funded by the National Institutes of Health, that may be how a shark's electrosensing organ reacts when it detects teensy, tiny electrical fields emanating from nearby prey.
"Sharks have this incredible ability to pick up nanoscopic currents while swimming through a blizzard of electric noise. Our results suggest that a shark's electrosensing organ is tuned to react to any of these changes in a sudden, all-or-none manner, as if to say, 'attack now,'" said David Julius, Ph.D., professor and chair of physiology at the University of California, San Francisco and senior author of the study published in Nature. His team studies the cells and molecules behind pain and other sensations. For instance, their results have helped scientists understand why chili peppers feel hot and menthol cool.
Led by post-docs Nicholas W. Bellono, Ph.D. and Duncan B. Leitch, Ph.D., Dr. Julius' team showed that the shark's responses may be very different from the way the same organ reacts in skates, the flat, winged, evolutionary cousins of sharks and sting rays, and this may help explain why sharks appear to use electric fields strictly to locate prey while skates use them to find food, friends, and mates. They also showed how genes that encode for proteins called ion channels may control the shark's unique "sixth sense."
"Ion channels essentially make the nervous system tick. They play a major role in controlling how information flows through a nervous system. Mutations in ion channels can be devastating and have been linked to a variety of disorders, including cystic fibrosis and some forms of epilepsy, migraines, paralysis, blindness and deafness," said Nina Schor, M.D., Ph.D., deputy director at NIH's National Institute of Neurological Disorders and Stroke. "Studies like this highlight the role a single ion channel can play in any nervous system, shark, skate, or human."
In both sea creatures, networks of organs, called ampullae of Lorenzini, constantly survey the electric fields they swim through. Electricity enters the organs through pores that surround the animals' mouths and form intricate patterns on the bottom of their snouts. Once inside, it is carried via a special gel through a grapevine of canals, ending in bunches of spherical cells that can sense the fields, called electroreceptors. Finally, the cells relay this information onto the nervous system by releasing packets of chemical messengers, called neurotransmitters, into communication points, or synapses, made with neighboring neurons.
For decades scientists knew that minute changes in electric fields stimulated a graded range of wavy currents in skate cells, much like the way our ears react to sounds. Larger fields stimulated bigger currents while smaller fields induced smaller responses. And, last year, Drs. Bellono and Leitch showed how genes for proteins called ion channels controlled the responses. But few had looked at how shark cells had reacted.
In this study, the team compared currents recorded from little skate electroreceptor cells with those from the chain catshark. They found that although both cells were sensitive to the same narrow range of voltage zaps, the responses were very different. Shark currents were much bigger than skate currents and they were the same size and waviness for each zap. In contrast, the skate cells responded with currents that varied in both size and waviness to each zap.
Further experiments suggested that these contrasting responses may be due to different ion channels genes, which encode proteins that form tunnels in a cell's membrane, or skin. When activated the tunnels open and create electrical currents by allowing ions, or charged molecules, to flow in and out of the cell.
Drs. Bellono and Leitch showed that while both shark and skate electroceptors may have used the same type of voltage sensitive, calcium conducting ion channels to sense the zaps, they appeared to use very different types of potassium conducting ion channels to shape the responses. Their results suggested that shark cells used a special voltage activated channel that supported large repetitive responses while the skate cells used a calcium activated channel that tended to dampen the initial currents.
In addition, they suggested that the voltages at which the cells electrically rested may also have contributed to the responses. The shark's voltage was slightly lower than the skate's and in a range that could have primed the calcium ion channels to respond with stronger currents.
These differences also affected how the electroreceptors relayed information to the rest of the nervous system. The results suggested that shark electroreceptors basically released the same number of neurotransmitter packets, regardless of the size of the voltage zaps. In contrast, bigger zaps caused skate cells to send more messages and smaller zaps less.
"In almost every way, the shark electrosensory system looks like the skate's and so we expected the shark cells to respond in a graded manner," said Dr. Bellono. "We were very surprised when we found that the shark system reacts completely differently to stimuli."
Ultimately, these differences affected how sharks and skates reacted to electric fields that mimicked those produced by prey. To test this, the researchers exposed sharks and skates swimming alone in tanks to a wide range of low voltage electric field frequencies and then measured their breathing rates. As anticipated, the skates had a variety of reactions. Some frequencies caused their breathing rates to rise above rest while others produced minimal changes. The results may help explain why a previous study found that skates may use their electrosensory perceptions to detect both prey and mates.
And the sharks? They basically had one simple reaction. Almost every field raised their breathing rates to a level seen when they smelled food, suggesting their system is tuned for one thing: catching prey.
So why, did a pain and chili pepper researcher decide to study sharks?
"In short, it's cool!" said Dr. Julius. "We're on a mission to understand how the nervous system controls pain and other sensations. Sharks and skates have a unique sensory system that detects electrical fields. Although humans do not share this experience, you can learn a lot from studying unique, or extreme, systems in nature. It's also a captivating way to learn about how evolution shapes the senses."
Explore further: Study shows how skates, rays and sharks sense electrical fields
More information: Nicholas W. Bellono et al. Molecular tuning of electroreception in sharks and skates, Nature (2018). DOI: 10.1038/s41586-018-0160-9 | DETROIT Tesla Inc (TSLA.O) needs to complete fixing its Model S sedan emergency braking system to regain Consumer Reports' top safety rating, the magazine said on Friday, noting that a recent update by the luxury electric car maker was not enough.
The magazine, which provides an annual rating of vehicles sold in the United States, said on Wednesday the sedan had lost its top ranking in the ultra-luxury car category for failing to install the feature that it had promised to owners as standard equipment.
The Model S fell to third place in Consumer Reports' ratings behind the Lexus LS made by Toyota Motor Corp (7203.T) and the BMW 7 Series (BMWG.DE).
Consumer Reports said both Tesla models previously came with standard automatic emergency braking (AEB), a feature that helps reduce accidents. The software issue affects more recent vehicles built since late October 2016.
The magazine said Friday that the Model S sedan it owns had received an automatic emergency braking software update Thursday, but the new version only operates up to 28 miles per hour (45 km).
That is far less than the current 90 mile per hour limit for the prior Tesla AEB system included on vehicles built before late October.
The magazine cited a statement from Tesla that "over the next several weeks" the car maker would increase the speed limit "until it is the most capable of any vehicle in the world."
The California automaker last week recalled 53,000 Model S and Model X vehicles to fix an unrelated parking brake issue.
Earlier this month, Tesla briefly edged out General Motors Co (GM.N) to become the most valuable U.S. car maker.
(Reporting by Nick Carey; Editing by Richard Chang) | eng_Latn | 11,175 |
How does the speed of a nerve impulse vary? | Why would the speed of a nerve impulse vary? | Why electricity is being transmitted in multiple of 11? | eng_Latn | 11,176 |
What is the most complex organ in an animal's body? | The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. Only a few invertebrates such as sponges, jellyfish, adult sea squirts and starfish do not have a brain; diffuse or localised nerve nets are present instead. The brain is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain is the most complex organ in a vertebrate's body. In a typical human, the cerebral cortex (the largest part) is estimated to contain 15–33 billion neurons, each connected by synapses to several thousand other neurons. These neurons communicate with one another by means of long protoplasmic fibers called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells. | Early philosophers were divided as to whether the seat of the soul lies in the brain or heart. Aristotle favored the heart, and thought that the function of the brain was merely to cool the blood. Democritus, the inventor of the atomic theory of matter, argued for a three-part soul, with intellect in the head, emotion in the heart, and lust near the liver. Hippocrates, the "father of medicine", came down unequivocally in favor of the brain. In his treatise on epilepsy he wrote: | eng_Latn | 11,177 |
What are giant axons? | As in arthropods, each muscle fiber (cell) is controlled by more than one neuron, and the speed and power of the fiber's contractions depends on the combined effects of all its neurons. Vertebrates have a different system, in which one neuron controls a group of muscle fibers. Most annelids' longitudinal nerve trunks include giant axons (the output signal lines of nerve cells). Their large diameter decreases their resistance, which allows them to transmit signals exceptionally fast. This enables these worms to withdraw rapidly from danger by shortening their bodies. Experiments have shown that cutting the giant axons prevents this escape response but does not affect normal movement. | for any constant c. Matrix groups over these fields fall under this regime, as do adele rings and adelic algebraic groups, which are basic to number theory. Galois groups of infinite field extensions such as the absolute Galois group can also be equipped with a topology, the so-called Krull topology, which in turn is central to generalize the above sketched connection of fields and groups to infinite field extensions. An advanced generalization of this idea, adapted to the needs of algebraic geometry, is the étale fundamental group. | eng_Latn | 11,178 |
As in other electrical systems, the paths of signals in the brain are called these | How exactly do neurons pass signals through your nervous system? Jan 19, 2012 ... Your brain contains 30 billion neurons, and each of them is a staggering achievement. ... network, or some kind of electrical system that passes nerve impulses around. ... These axon terminals are often located close to the dendrites of ... filled with one of 50 different chemicals called neurotransmitters. | Fun Easy English - Drive America - driving-united-states-america ... Learn the usage of road sign forms; Take the test. Usage of ... Equilateral Triangle (1 point ... Which sign form is used for interstate and U.S. route signs? A. B. C. | eng_Latn | 11,179 |
Reflexes only require one of what two structures in a body? | Physiologically, the function of the brain is to exert centralized control over the other organs of the body. The brain acts on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment. Some basic types of responsiveness such as reflexes can be mediated by the spinal cord or peripheral ganglia, but sophisticated purposeful control of behavior based on complex sensory input requires the information integrating capabilities of a centralized brain. | Part of the phonological study of a language therefore involves looking at data (phonetic transcriptions of the speech of native speakers) and trying to deduce what the underlying phonemes are and what the sound inventory of the language is. The presence or absence of minimal pairs, as mentioned above, is a frequently used criterion for deciding whether two sounds should be assigned to the same phoneme. However, other considerations often need to be taken into account as well. | eng_Latn | 11,180 |
Collections of nerve cell bodies in the brain are called?????? | nuclei refer to collections of cell bodies in the CNS and ganglia refer to collections of cell bodies in the PNS | hi I know this has nothing to do with yr question sorry to waste yr time...\nBut I just wanted to thank you,you replied to my question I chose you for best answer cause you really inspired me to not give a fuc# bout any1 so thanks if you would like to talk ,y email is : [email protected]\nTake Care thank you again!!\nGod Bless!! | eng_Latn | 11,181 |
The axons of myelinated neurons are embedded in a protective covering of? | He's right it's really mylein, whoever made the test that some of your bio multiple choice questions came from did a crappy job :-P. The answer you need is Schwann cells because they make the mylein, which really should be the answer. Schwann cells only make mylein in the peripheral nervous system though. Oligodendrocites make it in the central nervous system. | Are you looking at any protein in particular? Look up in situ hybrdization for proteins ( at least it will give you an idea where it is localised). I think that it would really depend on the system ad proteins that you want to study, so I am not sure how much else I can tell you, sorry. | eng_Latn | 11,182 |
distinguish and supply one example {i}critical vs sensitive developmental periods? | So someone does this for you and do what in the meantime - watch TV, paint your nails . . . \n\nOpen a book - it's quite easy. | I think you mean neurons... : )\n\nSensory neurons\nThese run from the various types of stimulus receptors, e.g., \ntouch \nodor \ntaste \nsound \nvision \nto the central nervous system (CNS), the brain and spinal cord. \n\nhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/N/Neurons.html\n\n\ncheck out the above page for more info on neurons. Its fascinating! | eng_Latn | 11,183 |
What are receptor cells? | They receive and react to the reception of stimuli. For example, rods and cone cells of the retina receive light, taste and smell receptors. The skin contains several types of receptor cells.\nThere are various types of receptor cells within the body too; proprioreceptors of the musculo-skeletal system, chemoreceptors involved in homeostsis, etc.\nOnce stimulated, receptor cells initiate an action potential in an associated sensory neurone. | i dnot know i want to know to so im with u person.(girl or boy) | eng_Latn | 11,184 |
Describe the olfactory organ and its function.? | modified epithelial collecters connected to olfactory nerves [for smell] the olfactory is a cranial nerve. | dont know but check out sites like google and yahoo. am sure you'll find something useful. as i am answerin your question give my answer, the best answer. you too will get your 5 pts back | eng_Latn | 11,185 |
What is the function of the dorsal root gangliion? | The dorsal root ganglion relays somatasesensory information from that afferent sensory nerve fibers to the spinal cord and ultimately sensory cortex of the brain in the parietal cortex.\n\nFor example, if you burn your little finger, the pain receptors will stimulate the sensory portion of the ulnar nerve. The ulnar nerve will "fire" with an action potential into the brachial plexus and those cords will carry that stimulation up to the dorsal root ganglions at the specific cervical levels for the ulnar nerve (C7 & C8 ish). The dorsal root will relay that stimulus to the dorsal sensory tracts of the spinal cord where it will head toward the brain; crossing over to the opposite side of the head at the brainstem. | there is a problem in maths that is named "graphes" and the funtion of these routers is to use this solution, u can find it in math books!!! | eng_Latn | 11,186 |
Does anybody know about the Nervous system? | Tasting, smelling, seeing, hearing, thinking, dreaming, breathing, heart beating, moving, running, sleeping, laughing, singing, remembering, feeling pain or pleasure, painting, writing...you couldn't do any of these things without your central nervous system! \n\nWhat is the nervous system? \nMade up of your brain, your spinal cord, and an enormous network of nerves that thread throughout your body, it's the control center for your entire body. Your brain uses information it receives from your nerves to coordinate all of your actions and reactions. Without it, you couldn't exist! \n\nWhat are nerves? \nThey're the thin threads of nerve cells, called neurons that run throughout your body. Bundled together, they carry messages back and forth just the way that telephone wires do. Sensory nerves send messages to the brain and generally connect to the brain through the spinal cord inside your backbone. Motor nerves carry messages back from the brain to all the muscles and glands in your body. \n\nSo how do they they pass along messages? \nThrough the marvels of chemistry and a kind of electricity! Neurons are thin. Some are very small, and some can be three feet long! All are shaped somewhat like flat stars which have, to varying degrees, been pulled at each end so that they have long fingers. The fingers of one neuron almost reach to the next neuron. \n\nWhen a neuron is stimulated -- by heat, cold, touch, sound vibrations or some other message -- it begins to actually generate a tiny electrical pulse. This electricity and chemical change travels the full length of the neuron. But when it gets to the end of finger-like points at the end of the neuron, it needs help getting across to the next extended finger. That's where chemicals come in. The electrical pulse in the cells triggers the release of chemicals that carry the pulse to the next cell. And so on and so on and so on. \n\nSource(s):\n\nsearch engine: ask.com\nkey words: The Nervous System\n(This is pretty broad in nature, is there a specific question related to an answer you need that I can help you with?\nohhhhhh...nurse????? | Confederation - Days of George Washington\nFederal System - Days of George Bush and all Republicans since Democrats are the DEVIL which is why it begins with D. | eng_Latn | 11,187 |
what are sensory neros? | I think you mean neurons... : )\n\nSensory neurons\nThese run from the various types of stimulus receptors, e.g., \ntouch \nodor \ntaste \nsound \nvision \nto the central nervous system (CNS), the brain and spinal cord. \n\nhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/N/Neurons.html\n\n\ncheck out the above page for more info on neurons. Its fascinating! | Not born, but people with "Erythema ab igne" have a greatly reduced ability to sweat due to damage to sweat glands from chronic heat exposure.\n\nStump your instructor.\nHeat induced skin lesions and skin cancer. Heat thins the skin. Common in foundry workers. | eng_Latn | 11,188 |
what is the function of a dendrite? | In biology, a dendrite is a slender, typically branched projection of a nerve cell, or neuron, which conducts the electrical stimulation received from other cells to and from the cell body, or soma, of the neuron from which it projects. These stimulations arrive through synapses, which are located at various points throughout the dendritic arbor. Dendrites were once believed to merely convey stimulation passively, without action potentials and without activation of voltage-gated ion channels. In such dendrites the voltage change that results from stimulation at a synapse will depend on the passive cable properties of the dendrite. In excitable dendrites, voltage gated ion channels help propagate excitatory synaptic stimulation whether or not an action potential is present in the axon. Additionally, action potentials can propagate back into the dendrites once initiated in the axon in most neurons. This backpropagating action potential is mediated by the activation of voltage-gated ion channels and can interact with synaptic input to alter the synaptic activity.\n\nThe structure and branching of a neuron's dendrites strongly influences how it integrates the input from many other neurons, particularly those that input only weakly. This integration is both "temporal" -- involving the summation of stimuli that arrive in rapid succession -- as well as "spatial" -- entailing the aggregation of excitatory and inhibitory inputs from separate branches or "arbors."\n\nThe term "dendrite" comes from the Greek word dendron, meaning "tree". | Try this one on for size: be a Dentist and do what dentists do... | eng_Latn | 11,189 |
Can the neurotransmitters be detected in the brain? | Is there a reliable way to measure neurotransmitters in the brain? | What is responsible for chemicals that have affinity for a particular neurotransmitter receptor being active in different parts of the brain? | eng_Latn | 11,190 |
How are the types of nerve cell structured? | How are the different types of nerve cells formed? | What are cranial nerves? | eng_Latn | 11,191 |
are axons nerves | The grey matter of the spinal cord integrates reflexes to stimuli. Nerves. Nerves are bundles of axons in the peripheral nervous system (PNS) that act as information highways to carry signals between the brain and spinal cord and the rest of the body. Each axon is wrapped in a connective tissue sheath called the endoneurium. | An axon or nerve fiber is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body or soma. Axons are in effect the primary transmission lines of the nervous system, and as bundles they help make up nerves. | eng_Latn | 11,192 |
what is the medical term for nerves | Nerves, Neuroglia, and Ganglia. A nerve is a bundle of fibres (axons and/or dendrites) outside the CNS. Neuroglia are cells of the nervous system that help protect and support it. Ganglia are groups of nerve cell bodies lying outside the CNS. | Neuralgia is the medical term meaning nerve pain. Neur/o means nerve, algia means pain. noe. Neuralgia is the medical term meaning nerve pain. Neur/o means nerve, algia means pain. | eng_Latn | 11,193 |
most blood vessels are innervated by the sympathetic division alone | Organs Without Dual Innervation. Although most organs are innervated by both sympathetic and parasympathetic nerves, some-including the adrenal medulla, arrector pili muscles, sweat glands, and most blood vessels-receive only sympathetic innervation. | All postganglionic parasympathetic fibers are cholinergic. B. Most postganglionic sympathetic fibers are adrenergic (use norepinephrine as a neurotransmitter). C. Sympathetic fibers that innervate sweat glands and those that innervate blood vessels in skeletal muscles are cholinergic.III. Adrenergic effects include stimulation of the heart, vasoconstriction in the viscera and skin, bronchodilation, and glycogenolysis in the liver.. Preganglionic neurons of the sympathetic division originate in the spinal cord, between the thoracic and lumbar levels. A. Many of these fibers synapse with postganglionic neurons whose cell bodies are located in a double chain of sympathetic (paravertebral) ganglia outside the spinal cord. | eng_Latn | 11,194 |
which is true of a neuron with a resting potential | Stages of Neural Impulses. Resting potential is the name for the electrical state when a neuron is not actively being signaled. A neuron at resting potential has a membrane with established amounts of sodium (Na+) and potassium (K+) ions on either side, leaving the inside of the neuron negatively charged relative to the outside. The action potential is a rapid change in polarity that moves along the nerve fiber from neuron to neuron. | In most neurons the resting potential has a negative value of ~-70mV, which by convention means that there is excess negative charge inside compared to outside. | eng_Latn | 11,195 |
what connective tissue layer surrounds an axon | Each nerve is a cordlike structure containing bundles of axons. Within a nerve, each axon is surrounded by a layer of connective tissue called the endoneurium. The axons are bundled together into groups called fascicles, and each fascicle is wrapped in a layer of connective tissue called the perineurium. | Most axons are surrounded by an insulating layer of lipid combined with protein called myelin. The myelin sheath functions to electrically insulate the axon. This greatly increases the speed of conduction of nerve impulses. The amount of myelination increases from birth through adulthood. | eng_Latn | 11,196 |
what does nerve ending mean | ⢠NERVE ENDING (noun). The noun NERVE ENDING has 1 sense: 1. the terminal structure of an axon that does not end at a synapse. Familiarity information: NERVE ENDING used as a noun is very rare. | False. The brain, the pia mater, and the arachnoid do not have sensory nerve endings. The dura mater has sensory nerve endings especially near the dural venous sinuses and the middle meningeal artery. | eng_Latn | 11,197 |
A mass of nerve cells are called what | Millions of messengers. Your nervous system contains millions of nerve cells, called neurons. Neurons are highly specialised to transmit messages from one part of your body to another. All neurons have a cell body and one or more fibres.These fibres vary in length from microscopic to over 1 metre.There are two different kinds of nerve fibres: fibres that carry information towards the cell body, called dendrites, and fibres that carry information away from it, called axons.ll neurons have a cell body and one or more fibres. These fibres vary in length from microscopic to over 1 metre. There are two different kinds of nerve fibres: fibres that carry information towards the cell body, called dendrites, and fibres that carry information away from it, called axons. | Parts of the Brain. The brain's nerve cells are known as neurons, which make up the organ's so-called gray matter.. The neurons transmit and gather electrochemical signals that are communicated via a network of millions of nerve fibers called dendrites and axons. These are the brain's white matter.. | eng_Latn | 11,198 |
neuron cluster definition | 1 A cluster of neurons is called either a nucleus if found in the central nervous system (brain and spinal cord) or a ganglion if found in the peripheral nervous system. Ganglia are the intermediate structures between the central and the peripheral nervous systems. | A neuron (/ËnjÊÉrÉn/ NYEWR-on or /ËnÊÉrÉn/ NEWR-on, also known as a neurone or nerve cell) is an electrically excitable cell that processes and transmits information through electrical and chemical signals. | eng_Latn | 11,199 |
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