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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1answer
880 views

Small vs Large neurons

What is the criteria for classifying neurons as small and large? Is this classification based on gross size or the length of axon? Do they have any physiological difference? For instance it is said ...
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Do brain cells regenerate in the adult brain?

I know that most cells in the body regenerate, dying and being replaced with new cells. For example, in bone special enzymes move radially outward from the marrow in a narrow tunnel, destroying the ...
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Are there animal species that sense infrared light with their eyes?

I asked a question earlier today about birds with infrared vision but this time I am asking about animals in general. I know that many snakes have receptors between their eyes and their snout that ...
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129 views

How does different sensory stimuli differ in nerve signal?

Every day, we experience different types of sensory stimulus, like heat, pain, cold, etc. However, in each case, the transmission of the stimulus to the brain through the neurones is carried on in ...
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Is C. elegans always observed with precisely 302 neurons? Are there ever individual viable exceptions?

This answer mentions that the C. elegans hermaphrodite has exactly 302 distinct neurons. This has made it a very effective model for a variety of types of biological research, including neurology and ...
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263 views

Are neurons roughly a magnetic dipole?

I would like to make a simulation (concerning genetic evolution) and I want to use a very simplistic model of neurons. I don't really care there are different kinds of neurons, I don't care much ...
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Why do myelinated axons conduct impulses faster? [duplicate]

How does the myelination help in better conduction? I would prefer answers that are not too technical please.
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4answers
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Are there organisms with fewer than 1000 neurons?

I'm developing neural networks comprised of just 3 to 10 layers of virtual neurons and I'm curious to know if there are any insect brains out there with fewer than a thousand neurons? Are there any ...
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1answer
147 views

Why is burn feeling 'slower' than touch?

When you touch a hot object you first feel the touch and only after a second you feel the burn too, and if you detach your skin from the object the burn feeling continues for few seconds. I remember i'...
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Cortical projections from layers 2/3 back to 4?

As all excititory neurons in layer 4 are stellate - they have no apical dendrites that could project to layers 2/3. However, I have seen some diagrams showing axonal projections from layers 2/3 back ...
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2answers
886 views

What is the specific role of the cerebellum when it comes to 'coordinating movement'?

In elementary biology (high school level in the UK - A levels), we are told that the cerebellum is the part of the brain that 'coordinates movement'. Literally nobody takes the time to explain what ...
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Why do I still see a bright light after looking directly at it?

When you look directly at a bright light, maybe accidentally when looking at the sun, the shape of the image may persistently be perceived even after you look away. Does this image persistence have ...
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What are the advantages of forgetting?

How forgetting things is helpful for the brain or the human body biologically? This web page After some moment of being rude, selfish, or weak, either we are able to put it behind us, or the ...
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645 views

Why is it possible to calculate the equilibrium potential of an ion using the Nernst equation from empirical measurements in the cell at rest?

In trying to understand the Nernst and GHK equations, I've hit upon a snag somewhere deep in my understanding of the subject matter. Scenario 1: when calculating the membrane potential of a living ...
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Why does the refractory period of neurons only allow signals to pass in one direction?

My textbook states that the advantages of the refractory period is that it means that action potentials are discrete and also that it results in signals only being able to pass one way, but provides ...
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2answers
744 views

Do lower animals have instinctive behaviors?

Can an organism such as C. elegans, with only 302 neurons, exhibit "instinctive or innate behavior"? If not, then at what basic minimal structure is instinct manifest?
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359 views

How do S and L cone cells sense colors like deep blue and red beyond their peak?

So I found this diagram of retinal cone cells: It looks like the S, M, and L cones peak at blue, chartreuse and orange, respectively. If so, how do we see colors past 575 nm and before 445 nm? If the ...
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835 views

How are neurons / synapses “biased”?

I'm trying to see if I understand this correctly. I've read the question Can the human brain be reduced to a binary system? and one of the answers explains: While action potentials are usually ...
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61 views

Why can nervous inflammation radiate symmetrically in the limbs?

I have had carpal tunnel syndrome in my hands this week, when the nerve in the pith of your palm, through thumb and index, is pinched, and swells, inside the wrist ligament tunnel. In a few days, ...
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Why are fearful stimuli more powerful at night?

For example, horror movies appear to be scarier when viewed at night than during broad day light. Does light have any role in this phenomenon? Are there changes in hormones at night versus during ...
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1answer
380 views

How is color information transmitted from the eye to the brain via the optic nerve? [closed]

I would presume that is has something to do with synapses and specific chemicals starting specific charges through the optical nerve's sub-components, and that this is somehow interpreted by the brain ...
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Is there an RGB equivalent for smells?

Millions of colors in the visible spectrum can be generated by mixing red, green and blue - the RGB color system. Is there a basic set of smells that, when mixed, can yield all, or nearly all ...
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1answer
2k views

What are Intersensory Associations?

While I was reading about "Neural Control and Coordination" I came across this "Association areas in the forebrain are responsible for complex functions like intersensory associations, ....." What ...
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1answer
670 views

How much does hearing deteriorate with age?

For the average person, what is the lowest volume of a pure tone at each frequency they can hear as a function of age? I know some people lose hearing faster than other people, because they are ...
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1answer
491 views

What is a starter cell?

I am reading the paper Cooperative Subnetworks of Molecularly Similar Interneurons in Mouse Neocortex and a term "starter cell" apears there (page 6): This yielded tissue sections where SOM or ...
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What is the perisomatic region of a neuron?

In the scholarpedia page on interneurons I encountered the following passage: The perisomatic domain is responsible for the summation of postsynaptic potentials arriving from all dendritic branches ...
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Cytochrome Oxidase activity in neuronal cells

The abstract of this article says "...the entire neuron is often not metabolically homogeneous; most of the oxidative activity is usually found in dendrites." Why would the activity of cytochrome ...
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1answer
69 views

Number of serotonergic neurons in mouse/rat DRN

What is the (approximate) number of serotonergic neurons in the dorsal raphe nucleus (DRN) of mice and rats?
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Is the central axon of pseudounipolar neurons in dorsal root ganglia typically myelinated

As I understand, sensory nerve cells in the dorsal root ganglion are pseudounipolar neurons, with a sole protrusion from the soma branching into a central axon (or functional axon) and peripheral axon ...
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Why don't we hear ultrasonic sounds as aliased versions of the original signals?

The upper limit of hearing is approximately 15 kHz, dependent on age and other factors. According to the principles of digital signal-processing, such an upper limit would mean that the auditory ...
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Dorsal root fibres

How can dorsal root fibres be unmylinated though are responsible for conduction of pain and temperature? How is their conduction so fast without even being myelinated? Is presence of only one axon( ...
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55 views

Hand motor control of the brain [closed]

I was watching a documentary (don't remember the name or the URL to the documentary) but they stated that the brain is layered and that each new layer is placed on top of the last. So the most ...
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Ion channels affected by gravity

In the literature I have found that action potentials behave differently when gravity is changed (cannot access fully). Action potential properties are gravity dependent. http://link.springer.com/...
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1answer
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Why is the human ear most sensitive to 4000 Hz tones?

Human hearing sensitivity is dependent on frequency, which can be visualized by equal-loudness (iso-loudness) contour plots. An example is given below (Taken from here). This plot shows that a tone ...
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1answer
237 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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1answer
61 views

Introducing evolution into the Hodgkin-Huxley equation

How would the Hodgkin-Huxley equation change when the geometry of dendrites and axons are introduced? Also can we model a situation of membrane activity during the corse of evolution, hence the ...
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75 views

Photoreceptors and light with mixed frequencies

I am interested in how the activation of a, say, blue cone depends on the incident light. Wikipedia tells me this: , which describes how strong the activation of the blue cone is for light with a ...
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1answer
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What is the connectivity between on-center & off-center bipolar cells?

Do rod-photoreceptors only form synapses with on-center bipolar cells (and on-center ganglion cells in the next step)? If so, why is that? Why do rod-cells only connect to on-center cells, while the ...
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1answer
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How does bath application of KCl depolarize a neuron?

Increasing extracellular KCl is often a way to depolarize neurons in experiments. My understanding is that increasing K+ extracellular concentration changes K+ reversal potential to more positive ...
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Why is the resonance frequency of a neuron defined by peak impedance?

I'm relatively new to the field of electrophysiology, so if anything is unclear or incorrect, please let me know. One thing that continues to confuse me throughout my reading is the property of ...
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1answer
381 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 ...
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1answer
46 views

Are memory updates local in mammals?

What I mean is, during long term potentiation (LTP) or long term depression (LTD) for a particular memory, do the strengthening and/or weakening of neuronal connections only occur in a small patch of ...
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1answer
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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 ...
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1answer
351 views

How does action potential conduct across a branch in a neuron?

As the action potential travel in the dendrite towards the cell body, it will encounter many branches. What happens at the branch? What makes it go to the cell body instead of other dendrite? Also, ...
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1answer
569 views

Can There Be Two Simultaneous Opposite Running Action Potential in One Axon

Can two action potential travel in the opposite directions simultaneous 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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3answers
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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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1answer
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How long does it take for dopamine to reach normal levels after a significant drop?

The building block sequence for is: Phenylalanine << Tyrosine << L-Dopa << Dopamine. It’s produced only in a few, very specific regions: Substantia Nigra and the Ventral Tegmental ...
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1answer
577 views

What do blue cone cells add to visual function?

First of all, I saw this other question in the SE sites with a good answer, but I didn't find an explanation about the blue cones specifically. So most human beings have 3 types of cones (cells ...
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1answer
732 views

What are different firing rates in different regions in the human brain?

Could it for example be that neurons that are concerned with high-order thought and medium-term planning fire more slowly, or is it expected that all neurons rather fire more or less at the same rate? ...
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General anaesthesia and brain cell damage [closed]

Do we lose brain cells when we undergo prolonged surgery under general anaesthesia?