Questions tagged [electrophysiology]

The study of the electrical properties of biological cells and tissues.

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Why did life not evolve to use radio?

We use electromagnetic communication everywhere these days. Cell phones, wifi, old-school radio transmissions, television, deep space communication, etc. I'm curious about some of the possible ...
Geuis's user avatar
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32 votes
3 answers
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Why is saltatory conduction in myelinated axons faster than continuous conduction in unmyelinated axons?

How does spacing apart sodium and potassium channels allow the action potential to travel faster down the axon? This is the reason always cited for saltatory conduction and myelination, but my mental ...
user7924's user avatar
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Why do blood vessels in the eye not obstruct vision?

As light enters the eye, it reaches the photoreceptors at the "base" of the retina, which then pass that signal to the bipolar and ganglionic neurons -- the latter of which send the signal ...
theforestecologist's user avatar
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1 answer
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Effect of pupil responses on the electroretinogram

The electroretinogram (ERG) is a measure of electrical activity of the retina. It is typically recorded from the cornea with a wire electrode or gold-foil electrode. Generally, the the ERG is ...
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Why is Fast Fourier Transform applied to raw EEG data?

I am trying to understand why Fast Fourier Transform (FFT) is used in the analysis of raw EEG channel data. My understanding (at the 30,000 ft view) is that FFT decomposes linear differential ...
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How is membrane capacitance related to the increased speed of saltatory conduction?

Here is the original question which inspired my question. As explained by the answers there, the reason saltatory conduction in myelinated neurons is faster than non-myelinated conduction is because ...
stochastic13's user avatar
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Is there a biophysical causation from local field potential (LFP) to spikes?

Many experiments showed that neurons tend to fire at some phase (usually trough) of local field potential (LFP) oscillations, such as theta or gamma rhythm. LFP is supposedly generated by a population ...
Memming's user avatar
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What keeps the resting potential of neurons constant at -70 mV?

I know the sodium-potassium pump pumps out 3 Na+ ions and pumps in 2 K+ ions per reaction so the negative charge in the axon increases. However, once the voltage (difference of charge inside and ...
hello all's user avatar
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8 votes
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Is "exhaustion" of the Hodgkin-Huxley membrane at constant stimulation a real phenomenon?

I was playing around with a simulation of the Hodgkin-Huxley model using their original parameters for the squid giant axon. By applying a constant stimulation current to the model in resting state, ...
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8 votes
4 answers
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How to analyse an ECG?

I have a project about extracting features from a homemade ECG. I need the PQRST points from the signal of the heart beat. The ECG I'm using has 3 electrodes that attach to the chest. The problem is ...
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What does pain look like in wave form?

I am interested in understanding what "pain" and "hot/cold" look like, as far as waves signatures (signal processing) go. My general understanding of how pain (nociceptive pathways) and hot/cold (...
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What is the reason behind high resting membrane potential of pacemaker cells?

Pacemaker cells have high resting membrane potentials of -50 to -40 mV, whereas normal cells have their resting membrane potential around -70 mV. Which ions, and what kind of channels are responsible ...
9Heads's user avatar
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1 answer
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Why do neurons have a negative resting potential?

Neurons expend the majority of their energy powering ion pumps to maintain the chemical gradients that power their electrical activity. To have a negative resting potential, neurons leak potassium ...
Luke's user avatar
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7 votes
2 answers
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Is there a biological neuron that spikes in response to hyperpolarizing currents?

As some background I've been building Electrophysiological models of neurons, and in the process stumbled upon a model, that in all respects is biologically plausible, but has a bizarre property I ...
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Why does the intensity of an action potential once generated at the trigger zone remain undistured throught the axon?

What causes this consistency? I read the previously asked questions on this site none of them carry an answer to this question.
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Why does hypercalcemia cause muscle weakness, yet hyperkalemia causes muscle excitation?

The reasoning I've been given is that high extracellular $[K^+]$ increases the $E_v$ of potassium; therefore, membrane potential increases and the threshold for action potentials is more easily ...
cash999's user avatar
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What signal processors comprise an Event-Related Potential system for EEG?

So my 30,000 ft. understanding of the EEG signal processing data flow is: Capture raw EEG data ("raw waveforms") Run these raw waveforms through a Signal Processing Framework that consists of 1+ "...
smeeb's user avatar
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Why does depolarisation by high intracellular K+ trigger calcium channels opening?

I have learnt that in pancreatic beta cells, glucose being metabolised in the cell causes a high ATP level, which triggers ATP-dependent potassium channels to close. This means that potassium can't ...
k--'s user avatar
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1 answer
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Where does this equation in the electrophysiology literature form come from?

In my studies I keep coming across the form of an equation that is used in many different mathematical models for voltage gated ion channels. The most general form I have found is in the 1977 paper ...
BioPhysicist's user avatar
6 votes
1 answer
151 views

Software recommendation for protein in electric field modeling? [closed]

I'd appreciate a suggestion for software to compare models of two proteins in an alternating electric field. The more detail, or perhaps direction towards an existing and similar paper, the better. ...
Timmons's user avatar
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1 answer
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Why do larger diameter myelinated axons have greater conduction velocities than small diameter myelinated axons?

A canonical statement I have frequently read is that "large diameter axons conduct action potentials at faster velocities than small diameter axons". After recently learning the effect of increased ...
S.C.'s user avatar
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2 answers
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Are there any organisms, extant or extinct, that have only one neuron?

Nervous systems are useful in one way because they allow for integration of complex information. They are also useful because they transmit information very rapidly, over a large distance. However, ...
StarlightDown's user avatar
6 votes
3 answers
10k views

What are tail currents?

This is a voltage clamp on an ion channel. When the voltage is stopped there is a still a current at the end (the tail current). I understand that the gates aren't completely closed because of which ...
Black Dagger's user avatar
6 votes
1 answer
175 views

Shouldn't recording electrode have as low resistance as possible?

Following quote is from this wikipedia page on single unit recording. Intracellular single unit recordings require electrodes be inserted through the cell membrane to record from within the cell. ...
bhyjnikm's user avatar
6 votes
1 answer
381 views

Criteria for compound action potential thresholds

As opposed to action potential thresholds (which are binary yes/no events), electrophysiological thresholds of compound action potentials are arbitrary. Mostly a certain noise level is picked and when ...
AliceD's user avatar
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6 votes
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Why Goldman Equation cannot be used to calculate dynamic changes of membrane potential

I'm reading about Goldman Equation and I've seen in some resources that it calculates the resting potential (not membrane potential in general) and that this equation cannot be used when membrane ...
Alexei's user avatar
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6 votes
1 answer
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How does the frequency of a visual stimulus affect the steady-state visually evoked potential?

I want to design a project for EEG signal processing. In my research I found the concept of SSVEP. SSVEPs represent the electrical activity of the brain as measured via EEG, and are evoked by visual ...
user8375's user avatar
6 votes
1 answer
712 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/...
Hans's user avatar
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1 answer
167 views

Organic battery?

Similar to the Matrix movie where humans were used as a source of electricity but different by using electric eels. Farmed like tuna what would be the electricity exchange to the food they eat?
Muze's user avatar
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5 votes
1 answer
225 views

How do plants store energy by potassium battery?

Plants have a so-called potassium battery system for energy storage/conversation. Wikipedia only has a reference to a technical article. Can someone explain it in a layman's language (or refer to a ...
LiamHor's user avatar
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5 votes
1 answer
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How's the membrane potential restored to resting state after hyper polarisation?

I have known for so long that Na+/ K+ pump restores the membrane potential. But as it pumps in 2 K+ for every 3+ Na+ moving out how can it make the membrane potential less negative when the net result ...
Tyto alba's user avatar
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If the average resting potential of a neuron is -70 mV, why is there such a high ratio of potassium ions inside relative to out?

My bio teacher was discussing the ratios of different ions inside versus outside the cell. $$\text{OUT:IN}$$ $$\text{K}^+ (1:20)$$ $$\text{Cl}^- (11.5:1)$$ $$\text{Ca}^{2+} (10000:1)$$ $$\text{Na}^+...
Stan Shunpike's user avatar
5 votes
1 answer
161 views

What physical or mental actions can be picked up by EEGs?

There certainly seem to be a lot of gadgets and gizmos leveraging EEG technologies to the control of devices. This makes me wonder: what intentions/thoughts can be captured by EEG technology, and ...
smeeb's user avatar
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5 votes
1 answer
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At What Rate Do Ions Leak Out of a Plasma Membrane Segment That Has No Ion Channels?

In reading about the purpose of myelin during action potential propagation, I came across a point of confusion. From what I understand, one of the primary "benefits" of myelin is that it aids in ...
S.C.'s user avatar
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5 votes
2 answers
140 views

How is the electrical potential difference distributed between two stimulating electrodes?

Suppose I set the voltage value of an isolated stimulator with a floating ground. I place one electrode above the spinal cord (positive) and the other placed subcutaneously far away from the spinal ...
user48114's user avatar
5 votes
3 answers
193 views

Can neurons be inhibited with electric current?

It is well known the electricity can be used to fire neurons. But can it be used to inhibit neuronal firing? This is in the context of extracellular stimulation. In extracellular stimulation, it is ...
azxsw's user avatar
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5 votes
2 answers
2k views

Mechanism behind negative conductance of ion channels

I am struggling to understand negative conductance shown on I-V curves on ion channels. Mechanistically, negative conductance means that inward (or outward) current increases when voltage across ...
Dilawar's user avatar
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5 votes
1 answer
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How do inward rectifier potassium channels work in the heart?

Apparently in cardiomyocytes, there is an inward rectifying potassium channel that operates during phase 4 of the cardiomyocyte action potential. I have heard that despite this potassium channel ...
Kenshin's user avatar
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5 votes
0 answers
133 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 ...
Léo Léopold Hertz 준영's user avatar
4 votes
1 answer
117 views

Why isn't there any repulsive force between Na+ and K+ disrupting thier roles in transmembrane voltage/ action potentials

Pretty self explanatory question. I have a basic grasp on the "How" and "Why" of Reversal/Action Potential in and between neurons, but this question lingers.
user972's user avatar
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4 votes
1 answer
187 views

Do electric eels produce current as they just move about, and how/why?

https://www.youtube.com/watch?v=y9wktSQdyaE This video demonstrates how an electric eel can supposedly produce up to 800 watts, and power a Christmas tree, which is very topical (a late Merry ...
Johnny's user avatar
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4 votes
2 answers
576 views

Are Gram negative bacteria classified as such because of their negative membrane potential?

Does the membrane potential usually quoted for Gram negative bacteria (e.g., E. coli) refer to the potential across both membranes? - If yes, then does the potential fall more over the inner or outer ...
someone's user avatar
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4 votes
2 answers
4k views

Action potential changes in low sodium concentrations but constant osmotic pressure

If I bathe a squid axon in a fluid that has high sodium concentration , why does the duration of action potential decrease compared to a control experiment in low sodium bath but maintained at the ...
Curious's user avatar
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4 votes
1 answer
76 views

Ischemia-induced deploarization in excitable cells

I have read in many sources that ischemia-induced depolarization is due to the opening of ATP-sensitive potassium channels and inactivation of Na/K exchangers [1,2]. However, K-atp channels are inward-...
kljiuklk 1's user avatar
4 votes
1 answer
118 views

Which kind of electrical brain activity is associated with consciousness and why?

According to this article The ethical brain At the end of the week 5 into the 6 (42-43 days) the first electrical brain activity occurs in a pre-born developing human. And according to the same ...
Pablo's user avatar
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4 votes
3 answers
173 views

Connect the inner and outer space of cell with a wire, will there be electricity?

There is a potential difference, but ions can not go through wires, right? Though there is a electric field, but there is no electron source, I am thinking the answer is no, or will there be some ...
Ziqian Xie's user avatar
4 votes
1 answer
132 views

Why does the nerve action potential needs potassium?

When looking at the action potential generation I do not understand why potassium is needed. I know that potassium is used to repolarize the cell. But why are sodium channels and/or sodium pumps not ...
Marijn 's user avatar
  • 2,765
4 votes
1 answer
865 views

Mechanisms of extracellular stimulation of neurons

When stimulating a group of neurons with an electrode, let's say we put it in a region that contains axons, what is the mechanism by which the axons are stimulated? I've been told electrodes (...
Pepe Mandioca's user avatar
4 votes
2 answers
5k views

Why nerve fibre is infatiguable?( is my conjecture correct?)

According to this: A nerve fibre cannot be fatigued, even if it is stimulated for a long time. This property of infatiguability is due to absolute refractory period. How is refractory period ...
JM97's user avatar
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4 votes
2 answers
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Sodium concentration during action potential generation

At the peak of the graph, is the concentration of Na+ outside the cell more than inside? That must be to overcome the electrical force in the opposite direction. When is the concentration of Na+ ...
user3733086's user avatar