Skip to main content

Questions tagged [electrophysiology]

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

Filter by
Sorted by
Tagged with
0 votes
1 answer
48 views

Using Nerve Conduction Studies to determine nerve regeneration

I was reading a paper investigating using MRI as a way to determine peripheral nerve regeneration: https://sci-hub.do/10.1016/j.expneurol.2009.10.012 They mention that ... nerve conduction studies ...
1 vote
0 answers
46 views

Opening probability of a voltage-dependent ion channel

Does the opening probability of a voltage-dependent ion channel depend on the unitary conductance? I think so because of the equation: but I am not sure.
0 votes
1 answer
22 views

Potassium Permeability in Cardiac Muscle Cells

From my research it seems as though there's a difference between cardiac and skeletal muscle cells in that during depolarisation, the permeability of potassium actually decreases for cardiac muscle ...
1 vote
1 answer
47 views

Mapping Ion Channel mRNA Copy Number to Channel Conductance

At least in invertebrates, it appears that within identified cell types, there are robust correlations between ion channel mRNA copy number (as identified by single-cell qRT-PCR) and the maximal whole-...
1 vote
1 answer
170 views

Why don't membrane potentials violate the principle of electroneutrality?

The principle of electroneutrality states that the number of anions and cations in a solution must be the same, i.e., that there will be no charge excess in any side of the membrane separating two ...
3 votes
2 answers
82 views

Why is the ordinary cardiac muscle’s target value of the action potential 0mV?

Why do some excitable cells have a target of 0mV for the action potential, even with a slight overshoot? Excitable cells such as muscles and nerves have the ability to rapidly change their membrane ...
2 votes
1 answer
55 views

Why do V_Na and V_K stay unchanged in Hodgkin-Huxley model?

In the Hodgkin-Huxley model, ionic current $i_\mathrm{Na}$ and $i_\mathrm{K}$ are given by $$ i_\mathrm{Na}=g_\mathrm{Na}(V_\mathrm{m}-V_\mathrm{Na})\\ i_\mathrm{K}=g_\mathrm{K}(V_\mathrm{m}-V_\mathrm{...
0 votes
1 answer
28 views

Why is there a negative sign before voltage in the gate variable functions of the Hodgkin-Huxley model?

In Hodgkin and Huxley's articles (1952, J. Physiol.; 1990, Bulletin of Mathematical Biology), the gate variables are formulated as In particular, as $V$ increases, $\alpha_n$ decreases and $\beta_n$ ...
6 votes
1 answer
304 views

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 ...
1 vote
0 answers
23 views

Electrodes for electroporation of bacterial cells

Wikipedia says "The process {electroporation} requires direct contact between the electrodes and the suspension." However I've read the process is an effect of the field strength alone, ...
33 votes
3 answers
36k views

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 ...
0 votes
0 answers
57 views

Confusion regarding the role of the capacitor in the electrical equivalent of a membrane

I am having trouble understanding the electrical equivalent of a cell mebrane as it is shown in this picture taken from Kandel: What I cannot understand is the capacitor in the specific image. Why is ...
0 votes
1 answer
45 views

Heart rate sensor electrodes to be used for blink detection (simple EOG)

I have a cheap ECG/HRV/heart rate sensor module for Arduino, bought from Aliexpress. It has 3 electrodes: RA, LA, RL, which I guess mean right arm, left arm, right leg. The module outputs one single ...
25 votes
2 answers
4k views

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 ...
3 votes
1 answer
359 views

Why do larger neurons have less cytoplasmic resistance?

I'm studying neuron electrochemistry rn and my book basically says that the more the cytoplasm impedes the flow of ions, the slower conduction will be, therefore larger neurons will have lower ...
-1 votes
1 answer
46 views

Can a dead fish be made to twitch via electrostimulation?

Galvani in the 1700s famously showed that a dead frog can be made to twitch by electric stimulation. The hind legs are particularly susceptible. Salt helps in the activation, as shown in these videos: ...
4 votes
1 answer
78 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-...
2 votes
0 answers
38 views

conduction in unmyelinated axons

(Not a specialist here) Several questions touch the voltage propagation along an unmyelinated axon, but I'd like to focus on the following. How fast does the voltage of a sub-threshold perturbation ...
4 votes
2 answers
4k views

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+ ...
3 votes
1 answer
150 views

What's the effect of prolonged threshold stimulus currents on action potentials?

I've been confused as to what exactly occurs when a current is injected into a membrane, throughout the duration of an action potential. My main source of confusion has been trying to reconcile 2 ...
3 votes
1 answer
63 views

Stimulus currents and neuronal responses

As I understand it, if a subthreshold current of unlimited duration is injected in a neuron, a passive response is observed, like an RC circuit. The membrane potential is depolarized by some arbitrary ...
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 ...
1 vote
0 answers
827 views

Measuring a plant's electric activity any instructions where to place electrodes?

I would like to measure a plant's electric activity / voltage, I've looked online to find out where to place the electrodes and what type of electrodes to use but they seem to very wildly. Any ideas? ...
2 votes
2 answers
801 views

Why are nerves blocked even though potassium channels are not blocked?

One could read "Local anesthetics produce a very slight, virtually insignificant, decrease in potassium (K+) conductance through the nerve membrane." At Handbook of Local Anesthesia 7th ...
0 votes
0 answers
29 views

How Fast can the Electrochemical Gradient on a Neuron be Reestablished? [duplicate]

The electrochemical gradient of Na+, K+, Ca2+, and Cl- between the inside and outside of a neuron is vital for its function. When a neuron fires, this gradient reverses. How long does it take for the ...
5 votes
2 answers
141 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 ...
2 votes
1 answer
383 views

Why does increasing the space constant increase conduction velocity in myelinated neurons if nodes of Ranvier are constantly spaced?

If depolarisation at one node of Ranvier triggers, by passive conduction, an action potential at the next node of Ranvier, why does increasing the space constant increase conduction velocity? Surely ...
1 vote
1 answer
405 views

GHK Equation and Action potential

Can GHK equation be used to predict the membrane potential even if the cell is not at resting state? To say it again, can we use GHK equation at every moment during Action potential? I'm confused ...
2 votes
1 answer
647 views

Help me understand voltage patch clamping

Before I type my question it is important to know that I already tried looking this up on my own and could not find an answer because the answers are all in complicated physics terms and this topic is ...
1 vote
0 answers
20 views

Potential obstacles to growing nanoelectronics within living cells? [closed]

Say there was a nanotechnology allowing to "grow" and wire up electronic components/sensors measured only a few nanometers in cross-section, though spanning in length across microns. Say ...
2 votes
2 answers
2k views

How many Watt-hours can an electric eel produce in a day?

Electric eels are cited as being about to produce about 860 watts of energy. But I haven't been able to find information on how long they can sustain their charge. https://www.youtube.com/watch?v=...
2 votes
0 answers
33 views

Can high energy photoelectrons damage cell membranes?

I've read that in addition to ionizing radiation causing damage to DNA through direct absorption, but DNA can also be damaged through photoelectrons with enough energy. The thing I was wondering is ...
4 votes
1 answer
190 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 ...
1 vote
1 answer
87 views

What is happening at the electrode interface when the electrical field is modified due to the change of ion concentration after an AP?

I have been working for quite a while now on electrophysiology and electrode fabrication. I studied what is happening at the neuron level during an action potential (polarization/depolarization, ...
4 votes
1 answer
373 views

electrostatic charge of viruses, especially Coronaviruses

I am searching for (and failing to find) literature about the electric charge (+/-) of viruses, specifically the Coronaviruses. I am aware that it is a complicated issue, including interaction of pH ...
2 votes
0 answers
60 views

How can I simulate heart electrical activity in a 2D plane?

I am not a biologist/medical student, I study software engineering. But I really like when medicine and engineering hold their hands together to achieve great things. As a side/toy project, I was ...
-1 votes
1 answer
88 views

What's a cells membrane potential without any leak channels?

Consider the following ion concentrations on either side of a cell membrane (in = inside cell, out = outside cell): $[\text{Na}^+]_{\text{in}} = 10mM$, $[\text{Na}^+]_{\text{out}} = 142mM$, $[\text{K}^...
0 votes
1 answer
433 views

What is a "membrane holding potential"?

What is a membrane holding potential? I have come across this term but haven't been able to find a definition. From "Voltage-gated sodium channels as therapeutic targets in epilepsy and other ...
1 vote
0 answers
22 views

Is there a way to derive Bazett's formula to correct QT interval in ECG?

As we know that QT interval in ECG is a function of heart rate (HR) and to comment on the pathology associated with altered QT interval, we must neutralise the effect of HR. For this Bazett's formula ...
0 votes
0 answers
31 views

How do I stimulate a neuron extracellularly, specifically the sphenopalatine ganglion

Apologies if this is too basic of a question, but I am an electrical engineer, just getting into neuromodulation/neurostimulation. For my senior project, I am trying to make a device that stimulates ...
1 vote
1 answer
360 views

Why is the current flow shown to be flowing from the negative area towards the positive area?

When I was studying the ECG chapter in the book "Guyton and Hall Textbook of Medical Physiology", I noticed something odd in one of the pictures: As you can see the current is shown to be ...
2 votes
1 answer
177 views

Why Is Action Potential Propagation Not Described by Telegrapher's But Cable Equation?

In modelling the propagation of action potential in an axon, why is the partial differential equation the cable equation rather than the telegrapher's equation? The difference between the two is that ...
6 votes
1 answer
722 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/...
1 vote
2 answers
748 views

At small axon diameters (<1 µm), why does myelination not increase neuronal conduction velocity?

As per the diagram below (and other graphs available online), why do unmyelinated fibres have a higher conduction velocity than myelinated fibres when the axon diameter is less than around 1 µm?
0 votes
0 answers
40 views

Effect of opposing electric charges on cells

Is the affect on a cell between two negatively charged plates theoretically similar to between a positively and negatively charged plate? In other words, would it induce charges on the inside and ...
0 votes
0 answers
60 views

Is there a proton gradient across the cell membrane, just like for the mitochondrial membrane?

Mitochondria have a proton gradient, is there also a proton gradient between cells and the extracellular medium?
3 votes
1 answer
1k views

What is the significance of the amplitude of brain waves?

What does the amplitude of brain waves represent and to what neuronal activities is this amplitude related to? For example, in a hypothetical situation, the frequency of brain waves is kept the same, ...
1 vote
1 answer
43 views

Question about the Derivation of the cable equation for neurites

I read in Wikipedia how the cable equation was derived (here) and had a specific problem regarding one of its equation: At the start of the derivation it states that we first need to pretend that the ...
1 vote
1 answer
256 views

Why the length constant of passive current flow isn't depend on the membrane capacitance?

I read that the equation for the length constant for passive conductance along a neuron depend on the resistance of the plasma membrane, the intracellular axoplasm and the extracellular medium. My ...
0 votes
0 answers
33 views

Does the zeta potential of a nanoparticle generally take into account ligand charge?

For example, if I had a quantum dot nanoparticle with conjugated linker peptides capped with polyarginine tracts. Would the localization of negative charge from arginine change the zeta potential ...