Questions tagged [electrophysiology]
The study of the electrical properties of biological cells and tissues.
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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 ...
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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{...
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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 $\beta_n$ ...
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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 ...
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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, ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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:
...
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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-...
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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 ...
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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+ ...
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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 ...
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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 ...
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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 ...
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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?
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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=...
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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 ...
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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 ...
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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, ...
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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 ...
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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 ...
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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}^...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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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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?
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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 ...
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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?
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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, ...
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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 ...
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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 ...
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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 ...
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In the PR segment of an ECG, how come there's no current flowing?
I don't really know how to phrase the question, but to put it as clearly as I can, I don't get why it is the P wave "flattens down" when the atria have completely depolarized. I get that the ...
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How does a microelectrode work?
On Wikipedia, the entire microelectrode page states only the following:
A microelectrode is an electrode of very small size, used in electrophysiology for either recording of neural signals or ...
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Physiology of hyperpolarization
In my textbook, it is stated that after the closure of potassium voltage-gated channels and during hyperpolarization, potassium leakage channels allow potassium influx passively and this returns the ...
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Difference between Premature Atrial Contraction and Atrial Fibrillation
what is the difference between Premature Atrial Contraction and Atrial Fibrillation. I know that both have irregular heart beat but have normal QRS complex. Both have abnormal or absence P waves but a ...
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