Questions tagged [action-potential]

A rapid change in the membrane potential of excitable cells such as neurons and muscles; this usually involves a steep rise (depolarization) followed by a steep fall in membrane potential (repolarization). The cell subsequently enters a short refractory period (hyperpolarized state) during which it cannot generate another action potential.

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11
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1answer
784 views

Purpose of K+ channels in action potential

I understand that they serve to repolarize the neuron after the Na+ influx. What I don't understand is why this is important. Meaning, let's say all the K+ channels disappeared. So now the ...
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1answer
556 views

Why summation takes place at Initial segment?

I know that many EPSPs summate at initial segment to produce action potential. But I don't understand why if EPSP can travel from dendrite to initial segment, then why it doesn't travel further? ...
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2answers
128 views

How does entry of Ca²⁺ to the myocardiocyte make it more contractible?

I'm trying to understand why an increase of Ca2+ entering into the cell, increases the force of the heart contractions. Based on what I have watched in many lectures videos on Youtube (this one- "...
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0answers
78 views

Accumulation of Na⁺ and Ca²⁺ in the myocardiocytes while having acute heart failure

Why is it necessary to have accumulation of sodium and calcium ions in the myocardium cells while having acute heart failure? Normally, at resting membrane potential, sodium and calcium are more ...
2
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1answer
136 views

What does the word “refractory” in “refractory period” refer to? [closed]

What does the word "refractory" in "refractory period" refer to? I know what it means "refractory period" (both, absolute and relative) in the action potential graph, but I don't understand what the ...
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2answers
11k views

Stimulating an axon causes impulses to travel both ways?

A diagram is presented as such above. The question given states What would be the effect of stimulation to cause a nerve impulse with a microelectrode at the middle of the axon? I thought the nerve ...
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0answers
74 views

About cell membrane; action potential and resting potential [closed]

Ion X is negatively charged and more concentrated inside than outside the membrane potential of a cell therefore Ex (equilibrium) is positive. Ion X is unknown. Why is the equilibrium positive?
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0answers
110 views

Elements that make action potential to conduct quicker? [duplicate]

The texts, online materials describe the velocity of conduction of action potential depends on axon's length and cross sectional area e.g. short length and large diameter decreases the resistance. ...
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0answers
57 views

Movement of few ion during changes in membrane potential

My question is very simple: why is it sufficient for a very few ions (such as 1 in 100000 K+) to move across the membrane to generate a remarkable variation in the membrane potential (like a change of ...
2
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1answer
2k views

Are Na+/K+ active pumps and K+/Na+ “Leak” channels same as given in the figure?

Na+/K+ channels maintain the resting potential with other sodium and potassium channels. Then what are these "Leak" channels? are they the same Na+/K+ pump in a special condition? If so, what is it? ...
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0answers
140 views

What is the derivation of the rules of proportionality between axon conduction velocity and diameter?

We have been told that in myelinated fibres, conduction velocity is proportional to the diameter of the axon. In unmyelinated fibres, velocity is proportional to the square root of the diameter. Can ...
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1answer
3k views

Why does an electric shock contract the muscle?

From what I understand, the electrical impulse in our nerve cells is not made of electrons, but of ions that move from different environments with different concentrations, which is totally not ...
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1answer
268 views

What is the mechanism by which myelination reduces the capacitance of the axon membrane?

There are two mechanisms that have been proposed to me. 1) Layering of Schwann cell membrane with conducting fluid between the layers is analogous to several capacitors in series. Since capacitance ...
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2answers
315 views

Do Schwann cells have Na+/K+ ATPase pump? [closed]

I was studying "Action Potential" and this question crossed my mind. Another question is that, "Why does the action potential not occur in Schwann cells, or if it does, how does it occur?" I know that ...
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1answer
209 views

Do action potentials cause the neuron to heat up as well as its environment?

I have read that we might be yawning to cool our brains down, so then a thought occurred to me. If we need to cool down our brain, then our brain but heat up for some reason. The only reason I could ...
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1answer
392 views

Inward rectifying potassium channels during undershoot of action potential

My professor said that inward rectifying channels help move the membrane potential back to the resting potential during the undershoot phase of the action potential. The membrane potential would have ...
6
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1answer
622 views

Can Two Opposite Running Action Potential Cross Each Other without Annihilation in One Axon

Can two opposite travelling action potential cross each other annihilation in an axon? My answer would be affirmative. If the propagation mechanism is linear as described by https://en.wikipedia.org/...
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1answer
291 views

How does stimulus reach neural threshold?

I understand that when the stimulus into a neuron is greater than the threshold it triggers the action potential. Do all the contributing stimulus have to occur at the same time, or can they occur ...
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0answers
262 views

FitzHugh–Nagumo system with diffusion

I was studying the FitzHugh-Nagumo model with diffusion and I quite do not understand the meaning of it. If we consider the system without diffusion, \begin{equation}\label{FHN}\begin{cases} \dot{u}=...
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1answer
2k views

How does a higher channel density increase speed of propagation of an Action Potential?

If there is a higher density of sodium channels then there will more Na$^+$ flux in the cell. So it's like trying to pass more material through a pipe and therefore the speed of action potential (AP) ...
2
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1answer
1k views

Why is active transport needed in repolarization?

During the repolarization phase of an action potential, the potassium ions diffuse out of the cell, and active transport begins. What I do not understand is why active transport is needed when the ...
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1answer
142 views

Concentration gradients across membranes with different ions

I'm trying to gain an intuition for the dynamics of across neuronal membranes. The overarching idea here is they are controlled by ion concentration gradients across the membrane (which we can ...
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0answers
34 views

Amount of Na+ needed to be transfered in order to depolarize the membrane?

I found out that the number of $Na^+$ ions that is needed to be transfered across the membrane to make it depolarized is a small number. In what way its proved? (Goldman equation maybe?)
8
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1answer
215 views

Original paper about the all or none law for neurons

I am looking for the original paper about the all or none law for neural activity. I know that there is a very old article about the all or none law for mammalian heart muscle fibers, but I'm ...
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0answers
138 views

Average Beginning of Action Potential in ECG by t-f HRV

I have some ECG data where I am estimating the average beginning of the action potential. I am interested in the discrete Fourier analysis of joint t-f HRV when input data is ECG. Frequency domain ...
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0answers
38 views

Membrane conductance in phase 1 of the cardiac action potential

Correct me if I am wrong, but in phase 1 of the cardiac action potential (for ventricle cells) there is flow of potassium ions due to the opening of transdent potassium channels. To me this would ...
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2answers
12k views

At what point during an action potential are the sodium potassium pumps working?

I'm trying to understand how all of the potentials during an action potential are created. My question specifically is about the sodium potassium pumps, however I would also be grateful if someone ...
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1answer
485 views

Dendrodendritic synapse through axodendritic synapse at same dendrite?

Reading Wikipedia's article of dendrodendritic synapse, I find that: Dendrodendritic synapses are activated in a similar fashion to axodendritic synapses in respects to using a chemical synapse. ...
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0answers
235 views

How does an increased amplitude affect nerve conduction velocity?

My professor said that increasing the amplitude (the amount of depolarization e.g. depolarizing from -80 mV instead of -50 mV) leads to a greater conduction velocity.
4
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1answer
839 views

If a blocker prevents repolarization, will the neuron be stuck in a depolarized state forever?

Potassium channels help to repolarize the cell after depolarization. But if the potassium channels are blocked, potassium ions cannot flow out of the cell to increase the membrane potential. Thus, one ...
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2answers
7k views

Do potassium channel blockers affect the resting membrane potential?

I am reading about scorpion venoms and toxins for my bio class and they appear to have a variety of potassium channel blockers. My professor asked "What effect would this have on a neuron?" and ...
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2answers
50k views

What is the difference between a graded potential and an action potential?

I was under the impression the only signals neurons send using changes in membrane potential are action potentials. But my biology professor showed us diagrams of graded potentials and action ...
8
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1answer
751 views

What recovers normal polarisation after hyperpolarisation?

I have been taught that a $\ce{Na+/~K+}$ pump helps to recover normal polarisation after-hyperpolarisation in neurones. I could not find out how it does that, since I've also been taught that such a ...
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2answers
4k views

How to conceptualize the action potential?

In my AP Biology class, we were taught that action potentials are not electrical impulses in the same way current travels through a wire. Rather, we were taught that action potentials are changing ...
4
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1answer
129 views

Oscillatory electrical system using a chain of neurons

Many daily activities that we perform are result of inbuilt oscillatory circuits in our body. For example walking, breathing, heart beat, blinking, etc. The coding and decoding of stored memory also ...
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1answer
1k views

Why does the membrane of a neuron not stay at its depolarized state?

When an action potential is transmitted along the axon, the membrane reaches its depolarized state by opening Na+ channels. Both K+ (potassium) and Na+ (sodium) are now on both sides with close to ...
4
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2answers
738 views

Could an action potential produce few or more neurotransmitters based on the stimulus received?

I reckon that if you would be able to widen the AP width, it would produce more neurotransmitters in that larger time interval. Is that correct? Or does the neuron have a standard amount of ...
2
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1answer
5k views

Why is pericardium muscle repolarizated earlier than endocardium? [closed]

I was reading about heat muscle contraction and I read: The endocardium depolarization happens earlier than pericardium , but pericarduim repolarization happens earlier, therefore the T wave in ...
4
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1answer
589 views

Why do the size of the phase 1 notch vary among cardiac cells?

The size of the phase 1 notch varies among cardiac cells. It is prominent in myocytes in the epicardial and midmyocardial regions of the left ventricular wall and in ventricular Purkinje fibers. ...
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2answers
186 views

Are Purkinje Action Potentials Neuronal and Cardiac?

I first thought that action potentials of His-bundle i.e. Purkinje fibers are Cardiac. However, I started to think that this is not enough. I think now that they are neuronal and cardiac. My ...
2
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1answer
51 views

Confusion over role of current/potential in Nervous system?

I am taking a course on the nervous system and I am do not have any physics background. Therefore, I would like to know, what are we precisely talking about when we talk about current in the nervous ...
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1answer
199 views

Does repolarization of muscle fibers mean that the muscle bundle is relaxed?

If I flex my bicep and continue to contract it does it mean that the muscle cells are in depolarizing state and not repolarizing?
0
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1answer
121 views

Cardiac Excitation Threshold - in C++ modelling [closed]

So I am trying to write a code in C++ about the cardiac excitation threshold. I know that this excitation threshold is the shortest stimulus2 value at which it can conduct an action potential (known ...
2
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1answer
234 views

All or nothing phenomena

We know that an action potential is produced by an active cell membrane when the stimulus reaches a certain threshold. When it does, an action potential fires, and when it doesn't, nothing happens. ...
2
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1answer
758 views

What is the mechanism responsible for the 'delay' in delayed rectifier potassium channels?

I've been trying to find a comprehensive explanation concerning the nature of the 'delay' in neurons' delayed rectifier potassium channels. As it's written in my intro to neuroscience textbook, these ...
8
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2answers
2k views

Can a single axon propagate multiple simultaneous action potentials?

I have not been able to locate any research that indicates whether a single axon of a neuron or nerve cell can conduct multiple simultaneous (i.e. spatially separate) action potentials. I am aware ...
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1answer
1k views

How does core-conductor model correspond to an actual neuron?

Hi guys, looking at your average neuron, it is very difficult for me to imagine how this could be translated into a core-conductor model On the neuron above, where would be the intracellular space ...
5
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0answers
126 views

How to measure Na/K channel activation at the membrane level?

Assume that there are two different signals occurring on the ECG - during depolarization and repolarization in the standard ECG. I was advised not to use the standard ECG in measuring the exact ...
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1answer
2k views

Mechanism of antiperistalsis

What is the mechanism of antiperistalsis that occurs during vomiting? Why the peristaltic waves normally don't propagate in anal to oral direction? Please give logical explanation with authentic ...
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1answer
2k views

Fastest and slowest action potential

When our instructor asked us about the speed of action potentials in cells, I told him that action potentials and two-wheelers travels at similar speeds. He thought that this is an 'interesting' way ...