Questions tagged [neurophysiology]

The study of the physiology of the nervous system, with emphasis on transcellular communication, and cellular and molecular processes involved in neural communication.

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465 views

What is the exact frequency of Delta brain waves during Slow Wave NREM Sleep?

I saw a TED talk about researchers playing pulsating pink noise while a test subject is in Stage 3 Non-REM / Slow Wave / Deep sleep and observing an increase in Delta wave EEG activity. This seems to ...
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Detailed working of the voltage-gated sodium channel

Hodgkin and Huxley formulated the ion currents through the three voltage-gated ion channels Na, K, and L as $$\sum_{k}I_{k}=g_{\rm Na}\,m^{3}h\,(u-E_{\rm Na})+g_{\rm K}\,n^{4}\,(u-E_{\rm K% })+g_{L}\,...
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1answer
86 views

Causes of the stochastic behaviour of voltage-gated ion channels

I came up with the following electro-mechanical model of a voltage-gated ion channel, resp. of its voltage sensor as described here and here. The voltage sensor is a bistable system with two local ...
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Why are there exactly 207 morpho-electrical types of neurons?

I'm taking an introductory neuroscience course online, and it mentions that of the 55 morphological types and the 11 electrical types, there are 207 morpho-electrical types. How does this work? 55 ...
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397 views

Visual phototransduction, neurons depolarization when no light: why?

While reading into visual phototransduction I was surprised to learn that photoreceptor cells are actually depolarized when there is NO excitation (no light, i.e. when you see nothing, black) and ...
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293 views

Why don't electric eels shock themselves?

Why do electric eels not stun or pain themselves when they discharge their high voltage shocks? While it is known that they use those high voltage shocks to track their prey (as discovered by my ...
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Electrical field stimulation of neurons: what are commonly used stimulation protocols and which are physiological?

I am doing a labproject with primary mouse nerve cultures (hippocampus and midbrain) and part of the experiments involve performing electrical field stimulation on these neurons. For now we have ...
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1answer
913 views

What gives nerves their silver colour?

I always thought the silver colour specific to nerves was due to the myelin sheaths, but I've observed that unmyelinated C fibres display that same silvery appearance. Where does this colour come from?...
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How do photoreceptors overcome the ambiguity of wavelength vs intensity to determine brightness? [duplicate]

I asked a similar question about the Principle of Univariance yesterday, but now I have another one. According to the Principle of Univariance, the input to a photoreceptor differs along two ...
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252 views

What is the neural coding of rod and cone cells?

In Rushton's paper on the Principle of Univariance, he states: Thus, though the rod input has two variables, wave-length and energy, the output differs only in one respect, namely 'brightness'. ...
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1answer
208 views

Understanding Hodgkin-Huxley's model and activation variables

This question is about the Hodgkin-Huxley model as introduced in Eugene M. Izhikevich, Dynamical Systems in Neuroscience, p.33 ff. I'm having trouble to understand and interpret the differential ...
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1answer
138 views

How fast the brain recover itself at sleep? What can be done to accelerate this process?

In Computer Science we have "Big O Notation" to describe how efficient is an algorithm at processing some task. Those can be linear, time constant, exponential among others. Using that analogy, How ...
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79 views

Confusion about the construction of the rat's mental map

I'm reading the article "A Topological Paradigm for Hippocampal Spatial Map Formation Using Persistent Homology" by Y. Dabaghian, F. Mémoli, L. Frank, G. Carlsson I try to understand the following ...
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1answer
101 views

Difference between spiking and firing

In the article "A Topological Paradigm for Hippocampal Spatial Map Formation Using Persistent Homology" by Y. Dabaghian, F. Mémoli, L. Frank, G. Carlsson I read some sentences with huge ...
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Functional role of the myelin sheath [duplicate]

One usually reads that the functional role of the myelin sheath is being a good insulator, accelerating the speed of action potential propagation along the myelinated axon. I tried to understand this ...
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How do firing patterns arise from the activity of many ion channels?

In his answer to another question, Bryan Krause says: Ion channels don't exhibit any firing patterns: neurons exhibit firing patterns that depend on all the channels present [...]. I understand ...
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Functional role of voltage-gated potassium channels

Having better learned here how action potential creation works in some detail, I'd like to pin down the functional role of voltage-gated potassium channels: they mainly shorten the time it takes the ...
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48 views

How are neuromodulator receptors distributed?

Irrespective of where, when and how neuromodulators are released, eventually they are detected by some receptors in the membrane of a target neuron (typically G protein–coupled receptors) ...
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972 views

Are centrioles really absent in human neurons?

A booklet (issued by my school) claims, Centrioles, formerly believed to be absent in neurons, have been described in neurons and may be associated with the production and maintenance of neuro(...
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46 views

Can action potential generating ion channels only be understood as assemblies of membrane proteins (and not as single proteins)?

I always believed to have roughly understood how voltage-gated ion channels and the creation of action potentials work: as and by single (or non-interacting groups of) membrane proteins, that behave ...
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Does GABA help or hinder anxiety?

This article https://www.prnewswire.com/news-releases/smartphone-addiction-creates-imbalance-in-brain-300558945.html Says both The researchers performed MRS exams on the addicted youth prior to ...
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1answer
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Typical firing patterns of (some) motor neurons

Since it is not so easy to imagine and visualize the behaviour of the muscles in the fingers, hand, and arm of a violinist performing a fast and accentuated trill vs. a slow and soft vibrato, I try to ...
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Are male and female brains physically different from birth?

Male and female brains are wired differently according to this article: Maps of neural circuitry showed that on average women's brains were highly connected across the left and right hemispheres, ...
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Why does a distraction cause a longer reaction time?

Does it have something to do do with the fact that the individual isn't concentrating on reacting to the stimulus, so it takes longer for it to be processed? How can this be out in terms of neurones ...
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1answer
181 views

How do nerve impulses travel so quickly?

Nerve impulses must travel incredibly fast to achieve the functions they do. However, I have been taught that sodium ions move down the axons by diffusion (thus causing depolarisation of the next part ...
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Why are some neurones unmyelinated?

As far as I am aware, most of the central nervous system consists of myelinated axons and most of the peripheral consists of unmyelinated. What is the reason for this? Would it not be more ...
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1answer
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Limits of phase-locking

In Rieke et al, Spikes, p. 31, I found this instructive picture showing and explaining phase-locking. I take it for granted, that phase-locking is possible only upto a maximal stimulus frequency (...
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How is Na concentration re-established after action potential

I understand that the repolarization is because some K+ chanels are opened with the action potential. But whats happens with the sodium chemical gradient that is needed for a new action potential? Are ...
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58 views

“Secondary refractory period” of class 1 neurons?

In Izhikevich's Dynamical Systems in Neuroscience, p. 199, one learns about a class of neurons that can be forced to fire with maximal frequency: Injecting a constant current of appropriate size (...
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1answer
365 views

Which function do nicotinic receptors have in the periphery?

I came across this question today, it says: Nicotinic receptors stimulation is directly responsible for ….... I should fill the spaces by one of the following choices: Increasing the excitability ...
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1answer
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What is the point in the Neuromuscular Junction?

Surely a direct connection (i.e. an electrical synapse) between motor neurone and the sarcolemma would allow for much faster neuromuscular transmission? It is my understanding that chemical synapses ...
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Why myelin sheat does not cover the whole axon?

Is there an optimal lenght for myelin sheats to be effective and lead potential across the nerve cell? This has always bugged me.
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135 views

Why are “itch signals” transmitted so slowly from the skin to the human brain?

In the second half of the BBC radio (and podcast) program Cats and Itch; Discovery, The Curious Cases of Rutherford and Fry Episode 2 of 5 the phenomenon and origin of the "itch" and related ...
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1answer
79 views

What are the response frequencies of sensory neurons?

Both visual and auditory stimuli are sent to the brain via ganglion cells (retinal resp. spiral). Both are the first cells along their resp. pathways that produce action potentials. My question ...
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167 views

Alpha-gamma co-activation

I am having trouble visualizing/grasping the necessity of alpha-gamma co-activation. My understanding is the following: When an external load causes stretching of the sensory muscle spindles, the 1a ...
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2answers
646 views

Can anyone explain the idea of anodic nerve stimulation?

Nerves get stimulated under the cathode, according to the conventional current direction. But in some research, it is said that anodic stimulation or anodic current stimulation can activate neurons. ...
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1answer
362 views

Where does the initial action potential come from?

When talking about action potentials we say that previous neurons caused an action potential in this neuron and that this neuron's action potential caused the same in further neurons. But what is the ...
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What is reaction time of a single c. elegans neuron?

What is the reaction time of a single c. elegans neuron? Is sensory neuron reaction to stimulus is similar to intermediate neuron passing a signal to motor neuron? What about chemical and electrical ...
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393 views

Why are the neurites from hair cells to spiral ganglion cells called axons?

In Kandel's Principles of Neural Science I found the following figure which shows the innervation of the organ of Corti: From the legend to this figure (30-10, p. 602): "The great majority of ...
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1answer
295 views

Will neurons die if they are inactive for a long time?

We know that when muscles are not used they atrophy. Does something similar also happen in neurons if they do not receive any stimulus?
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Are trees still carrying their leaves more likely to be felled by an autumn storm?

Is there evidence that trees still carrying their leaves are more likely to be felled by an autumn storm than trees already having lost their leaves? At first sight this seems plausible (and might be ...
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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 ...
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Question About the Physiology of Seizures

Absence seizures usually occur in children between ages 4 to 14 (Hopkins Hospital). Spontaneous remission occurs in 65–70% of patients during adolescence (Medicine Central). My question is what ...
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Interplay of neuritic and synaptic growth

Let me try to give a picture of my understanding of neuritic and synaptic growth and their interplay. Pick two neurons in corresponding areas of opposite hemispheres which are connected by a synapse (...
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1answer
156 views

Mathematical relationship between membrane conductance and conduction velocity?

By what factor would the myelin need to decrease membrane conductance (gm) if you wanted conduction velocity in a 10 μm myelinated mouse axon to be 100 times faster than in a 10 μm unmyelinated mouse ...
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1answer
34 views

Distribution of synapses of CA1 neurons

In the Wikipedia article on dendritic spikes I read: In the hippocampus, the CA1 neurons contain two distinctive regions that receive excitatory synaptic inputs: the perforant path (PP) through ...
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Focusing your attention on an area within your body, what effect does it make? [closed]

When I focus on tactile signals from a certain part of my body for a while (e.g. for one minute), this part of the body will usually become warmer. For example I can do that with a certain finger or ...
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3k views

If alcohol is a depressant, why does it makes certain people more hyperactive?

Alcohol is by traditional definition a depressant from what I have been taught, ergo it shows down CNS responses. However, why does alcohol then make some people act out and be more energetic than ...
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Distribution of dendritic spike generating ion channels on the dendritic tree

Is there evidence that dendritic spike generating ion channels are distributed unevenly on the dendritic tree, with higher density near the branching points of the tree than along the unbranched ...
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157 views

Half-life and production rate of ion channels

There are "not millions, not a few hundred...somewhere in between (some tens of thousands)" of ion channels in a neuron. Given the number of ion channels per neuron, knowing the half-life of ion ...

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