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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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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 ...
Vladimir Gritsenko's user avatar
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 ...
user7924's user avatar
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15 votes
2 answers
628 views

Is our color vision calibrated to sky, vegetation, and blood?

Our color vision is based on three types of receptors (cones) which are sensitive to three distinct locations on the spectrum: 420–440 nm, 534–555 nm, and 564–580 nm. We label them "red", "green", ...
SlowMagic's user avatar
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2 votes
2 answers
636 views

Why does resting potential not become continually more negative?

(Firstly, I know this is similar to other questions, but I have read those answers and they do not really cover this topic). My understanding of resting potential: action potential is not being ...
Ben Hughes's user avatar
71 votes
2 answers
26k views

What is the evolutionary advantage of red-green color blindness?

Red-green colorblindness seems to make it harder for a hunter-gatherer to see whether a fruit is ripe and thus worth picking. Is there a reason why selection hasn't completely removed red-green ...
Christian's user avatar
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10 votes
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Why does a light object appear lighter in your peripheral vision when it's dark?

So, I am not sure I can reproduce it via images, but the steps are: 1) At night, open a window and have a look at the surface of the earth 2) Suppose there's an object that reflects a tiny amount of ...
knitevision's user avatar
9 votes
3 answers
2k views

How do our eyes detect light at different frequencies?

Here is my confusion: we can see colored light of different wavelengths: form red to violet. To my understanding, these stimuli cause a confirmational change in the photoreceptors in our eyes and ...
Confusedbyeverything's user avatar
6 votes
1 answer
925 views

How does a change in the potential across a neuron's membrane get turned into a signal that is sent down the axon?

I understand How a signal is propagated down the axon. How the membrane potential of a neuron changes during the course of it's "firing". But I don't understand how physically the change in the ...
Stan Shunpike's user avatar
5 votes
1 answer
446 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 ...
D.J. Lawson's user avatar
64 votes
4 answers
9k views

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 ...
J.Todd's user avatar
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20 votes
1 answer
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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 ...
Mesentery's user avatar
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14 votes
2 answers
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How does a neuron change as you learn?

I am currently taking a course called "Introduction to Machine Learning with ENCOG 3", and I have a question about how well the Artificial Intelligence (AI) algorithm for a "neural network" ...
Greg Thatcher's user avatar
11 votes
2 answers
1k 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 ...
J.Todd's user avatar
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8 votes
3 answers
6k views

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 ...
Semper Ambroscus's user avatar
8 votes
3 answers
2k views

Advantage of opponent color?

Opponent process is a color theory that states that the human visual system interprets information about color by processing signals from cones and rods in an antagonistic manner (source). What is ...
Abalfazl Moridi's user avatar
7 votes
2 answers
2k views

Can a single axon propagate multiple simultaneous action potentials?

I have not been able to locate any research that indicates whether a single axon of a neuron or nerve cell can conduct multiple simultaneous (i.e. spatially separate) action potentials. I am aware ...
watsonic's user avatar
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1 answer
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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 ...
sebjwallace's user avatar
4 votes
1 answer
327 views

Why is peripheral vision not bleached by daylight?

In daylight, rods are known to be bleached: we have to wait some time after going into darkness before scotopic vision becomes effective. But, as I understand, peripheral vision is also mostly due to ...
Ruslan's user avatar
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4 votes
1 answer
3k views

Saltatory conduction of nerve impulses

I am aware about some basics of saltatory conduction of nerve impulses. I know that the nerve impulses (ion flow and the depolarization) are transferred from node to node in myelinated nerve fibers. ...
user avatar
4 votes
1 answer
3k views

If nerve consists of many axons, where are then their soma located?

This question has haunted me for two years. Wikipedia mentions : A nerve is an enclosed, cable-like bundle of axons (the long, slender projections of neurons) in the peripheral nervous system. A ...
user avatar
4 votes
1 answer
2k views

Why are Merkel cells innervated by an axon, and not a dendrite?

Here are two images from Google. Afferent neurons receive input and send it to the central nervous system. Input is received by the neuron's dendritic end and send away centrally via axon terminals ...
user4147's user avatar
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4 votes
2 answers
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What are the functions and differences between axons and dendrites?

My textbook doesn't do a very good job of pointing out what the differences between the two are. It basically mentions axons only in the same breath as the synapse (that synapses are the endings/tips ...
Lesbihonest's user avatar
1 vote
0 answers
64 views

Visual maps of the neuronal membrane

There are lots of visual maps of the brain as a whole, especially the cortex, that show the distribution of "features" over a two-dimensional map, e.g. the Brodman areas (their morphology and their ...
Hans-Peter Stricker's user avatar
0 votes
2 answers
209 views

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 ...
Hans-Peter Stricker's user avatar
83 votes
3 answers
15k views

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 ...
Spartacus9's user avatar
36 votes
2 answers
3k views

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 ...
uhoh's user avatar
  • 5,598
12 votes
1 answer
805 views

How does pressure travel through the cochlea exactly?

I cannot find this answer anywhere. What I do know is that the stapes pounds on the round window of the cochlea and this causes the fluid to move inside the cochlea itself, which has the three ...
user525966's user avatar
11 votes
1 answer
909 views

Purpose of K+ channels in action potential

I understand that they serve to repolarize the neuron after the Na+ influx. What I don't understand is why this is important. Meaning, let's say all the K+ channels disappeared. So now the ...
Jo.P's user avatar
  • 337
11 votes
3 answers
4k views

Does a neuron ever generate an action potential without stimuli?

Most accounts I read involving action potentials and synapses and the like tend to focus mostly on the action potential as a mere automatic reaction to another similar event happening upstream. From ...
Joebevo's user avatar
  • 849
10 votes
1 answer
14k views

Why can action potentials not be initiated at dendrites?

Why are action potentials not initiated at dendrites, although dendrites are the first to receive input from the presynaptic cell? In fact, excitatory postsynaptic potentials (EPSPs) at the dendrites ...
Curious's user avatar
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10 votes
1 answer
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What is the mechanism behind tinnitus?

I seem to have come across two contrasting explanations for tinnitus induced by loud noises- i.e. damage to the hair cells in the cochlea. On the one hand, I have read that damage to the hair cells ...
Meep's user avatar
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10 votes
1 answer
469 views

Does the nervous system have "routers"?

Does the peripheral nervous system have a system of routers that decide where a message is meant to go based on some kind of address, or does a signal from the brain follow a single, unbroken chain of ...
Raiden Worley's user avatar
9 votes
2 answers
2k views

Are unilaterally deaf people able to determine where sound comes from?

My question is on people deafened in one ear, but normal hearing in the other. Time and level differences between the two ears are only part of how the human body can localize the source of the sound....
Fofole's user avatar
  • 191
9 votes
1 answer
16k views

Are sensory receptors neurons?

Background There are many receptor types in the body, with various functions and various mechanisms of transduction. Receptor cells are considered to be part of the peripheral nervous system, as they ...
AliceD's user avatar
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8 votes
2 answers
567 views

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 (...
smeeb's user avatar
  • 639
7 votes
2 answers
913 views

What features cause mechano sensory adaptation?

In relation to mechanoreceptors (e.g. pacinian corpuscles), what stops a constant stimulus from producing action potentials? I understand that adaption is used to filter out stimuli that aren't ...
Will Perry's user avatar
7 votes
1 answer
1k views

How is color information transmitted from the eye to the brain?

Is color information sent from the eye to the brain frequency-modulated, or are different colors transmitted by different axons? I know that each ganglion cell is connected to multiple photoreceptors....
Anixx's user avatar
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7 votes
3 answers
1k views

What is the science behind the inaccurate perception of colors?

If I go into a green room (all walls are semitransparent and green) and spend some time - around 10+ min - in there, when I come out all my eyes see is white as pink. I see no (or very few other) ...
Tab's user avatar
  • 173
7 votes
1 answer
280 views

What is the biochemistry of love?

How is love induced between humans? Say, between mother and child, couples, etc. Does the phenomenon of love exist in other mammals, too?
San's user avatar
  • 523
7 votes
2 answers
1k views

Is the bipolar neuron of the retina considered a sensory neuron?

Any neuron that participates in sending impulses from receptors to the CNS are referred as sensory neurons. But I often see bipolar neurons of the eye (which according to the above definition should ...
deechitpoudel's user avatar
7 votes
1 answer
361 views

What color does the other cone in Tetrachromacy correspond to?

Human with normal vision possesses 3 cones, which correspond to blue (S), green (M) and red (L). What about tetrachromacy, where people have 4 cones in their retinae? What is the fourth cone exactly, ...
raisa_'s user avatar
  • 407
7 votes
2 answers
2k views

Latency differences between our senses

I would be interested in knowing how long it takes between the moment something touches our skin and the moment something is activated in the brain. Also how long does it take in total until we ...
Mehdi's user avatar
  • 245
6 votes
1 answer
382 views

Perception of white in the absence of rods

If the retina would not have any cones, one would be color blind. If white is the presence of all colors (in the matter of color mixture, not addition), then what would white look like without rods?
Muze's user avatar
  • 1
6 votes
1 answer
3k views

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 ...
Edward Garemo's user avatar
6 votes
2 answers
3k views

What causes the tonotopic organization of the inner ear?

I'm trying to understand why tones are registered in the way that they are in the inner ear, i.e., why are high pitched sounds sensed at the base of the cochlea and low frequencies in the apex? I've ...
Martin Swift's user avatar
6 votes
1 answer
2k views

Relationship between nerves and axons

I just wanted to get a realistic viewpoint of our nervous system. I understand arteries and veins, but I wanted to know how similar our nervous system is to that? I understand we have neurons (...
Singh's user avatar
  • 295
5 votes
1 answer
4k views

Can turkeys run around when their head is cut off like chickens do?

Chickens may run around after their head is cut off if the head is severed near the base of the skull leaving the brain stem intact and missing the jugular vein. This usually only lasts for a few ...
wanderweeer's user avatar
  • 2,743
5 votes
1 answer
315 views

Hodgkin huxley neuron not spiking consistently for currents greater than threshold?

Hi I am currently studying physics at the undergraduate level. As part of my final year project Ive got to implement the HH model and investigate certain types of behaviour. My issue is the following. ...
Vishal Jain's user avatar
5 votes
2 answers
3k views

Can axons act as receptors?

In all histology books, it is stated that all sensory nerve endings (receptors) consist of dendrites that translate physical stimuli from the environment into neural signals. However, several sensory ...
user4147's user avatar
  • 2,159
4 votes
0 answers
69 views

How widespread among mammals is the glymphatic system's metabolite clearance in the brain during sleep currently known to be?

The glymphatic system and "brain washing" (metabolite clearance) during mammalian sleep: Xie et al. (2013) Sleep Drives Metabolite Clearance from the Adult Brain (also here) has been cited ...
uhoh's user avatar
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