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.

Filter by
Sorted by
Tagged with
0
votes
0answers
24 views

Phantom Limb | Is that even possible?

I am fascinated by the fact that an amputee can control their robotic arm by thinking of the actions they would normally execute when the limb was present. The mind sends signals to the nerve endings ...
2
votes
1answer
129 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
1answer
615 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
2answers
23 views

Action potential attenuation in unmyelinated axons vs demyelinated axons

I learnt that action potentials travel much faster along myelinated axons, and when these axons are demyelinated the action potentials travel much slower and sometimes die out. Why do action ...
0
votes
0answers
17 views

Topography of motor deficit and spasticity in UMNS

As a medical student, I have been told that upper motor neurone syndrome is a cause of motor deficit and spasticity. The motor deficit is said to be affecting predominantly the extensor apparatus at ...
2
votes
2answers
208 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 ...
1
vote
2answers
16 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?
1
vote
1answer
27 views

Is magnetic resonance microscopy appropriate for investigating ion-channel flow?

I've been looking into ways to characterize the elecrophisiology of neurons for cell signaling and I came across magnetic resonance microscopy as a tool for gaining images of neuronal activiy at a ...
1
vote
1answer
53 views

Why are eyes more sensitive to flicker in periphery — contradictory answers

In terms of the perception of flickering by CRT monitors, This answer suggests that peripheral vision has faster response and is thus more sensitive to flicker due to being provided by rod cells. ...
7
votes
1answer
236 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?
-2
votes
1answer
30 views

Alternative hypothesis for learning in brain beyond the hebbian rule

I was reading on wikipedia that there are exceptions to the hebbian rule, and I was curious about the possibilities of other hypotheses of how learning occur in the brain. So I would like to know: ...
0
votes
1answer
32 views

What causes paresthesia from compression?

Compression of a nerve causes loss of afferent and efferent information in it. What is the physiological basis of this?
0
votes
0answers
17 views

Why are the sympathetic and parasympathetic axons different, in terms of presynaptic and postsynaptic length?

Does the parasympathetic system have a long presynaptic efferent axon because it takes a great distance to reach target organs from the brain stem or sacral region of the spine? Does the sympathetic ...
5
votes
1answer
97 views

Vitamin A Deficiency

I have a quick question regarding Vitamin A deficiency. The photoreceptor molecules in both rods and cones have the same general structure which is retinal which is bound to a protein called opsin ...
1
vote
1answer
44 views

Cardiac vs. skeletal muscle contraction

For the heart muscles, it is the extracellular Ca2+ that is necessary for the contraction, but for the skeletal muscles, it is intracellular Ca2+. One of my answers on a test was the following: "In ...
0
votes
0answers
19 views

Doubt related to nerve impulse transmission

Naturally, the extracellular fluid has more sodium ions and the axoplasm has more potassium ions. Since there are more potassium leakage channels than sodium leakage channels on axoplasm, it is more ...
1
vote
1answer
9k views

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 in only a few, very specific regions: Substantia Nigra and the Ventral Tegmental ...
0
votes
0answers
22 views

Silly question about two human mechanisms: induced “REM dreams” by masturbation?

First of all, I'm a layman concerning Biological discussion. Well, my question is simple: is there any relationship between the hormones liberated by masturbation and REM phase of sleep? I'm ...
2
votes
1answer
33 views

What does sympathetic and parasympathetic 'tone' mean?

My professor's lecture notes say that " The basal rate of firing is called “sympathetic tone” and 'parasympathetic tone" , but a table I found on the internet says that the parasympthetic system has ...
1
vote
1answer
23 views

Meaning of “external demands” in a paper describing the gut-brain axis

From "Brain Gut Microbiome Interactions and Functional Bowel Disorders": In response to external and bodily demands, the brain modulates individual cells (ECC – enterochromaffin cells; SMC – ...
0
votes
1answer
28 views

Why is the ratio between action potential and threshold value called the 'safety factor'?

"All­or­Nothing Principle. Once an action potential has been elicited at any point on the membrane of a normal fiber, the depolarization process travels over the entire membrane if conditions are ...
0
votes
0answers
12 views

Why does extracellular resistance matter?

The following equation describes a constant $\lambda$ that tells us about how far an electrotonic solution will travel. $$\lambda = \sqrt{\frac{r_m}{r_i + r_o}}$$ where $r_m$ is the resistance of ...
2
votes
1answer
47 views

Is breathing a reflex action or is it an intrinsic process?

The process of breathing is controlled by respiratory centers in the brain stem. Do these centers have an innate activity, i.e., just send out signals to breathing muscles intrinsically, and have the ...
1
vote
0answers
17 views

Biophysically, how to change from a tonically firing neuron to an occasionally firing one?

In terms of membrane properties, size and neuronal biophysics (assuming no change in incoming excitation), how can a tonically firing neuron become (say during development) an occasionally bursting ...
1
vote
0answers
22 views

Electrical transmission vs Chemical transmission

"The advantage of electrical transmission, apart from speed, is it can favour synchrony in firing. For example, in the brain stem a nucleus called the inferior olive can generate oscillations due to ...
8
votes
3answers
1k 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 ...
1
vote
1answer
20 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
1answer
63 views

By what physiological mechanism do we not feel microbes (bacteria, etc.) living on our skin?

Background I know our bodies have a handful of ways to threshold our awareness of sensory stimuli: Neural density Sensory acuity I assume really tiny stimuli could fit between receptors e.g., ...
1
vote
1answer
29 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 ...
1
vote
1answer
16 views

Is there any case in which excitability increases with lowering the RMP?

My professor says , at a more negative RMP, less sodium ion channels are inactivated, so if you take 2 of the exact same neuron with the same threshold potentials, and try to excite them starting from ...
1
vote
0answers
22 views

Help me understand Voltage Patch Clamping please?

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 ...
4
votes
1answer
3k views

What is it that specifically kills ALS patients?

ALS is a fatal motor neuron disease, and even though there are many different articles out there on the topic "How does ALS actually kill you?", none of them really delve deep enough into biology to ...
26
votes
3answers
29k 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 ...
4
votes
1answer
2k 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 ...
3
votes
0answers
70 views

What does myelin insulate against, exactly?

I am aware of the saltatory conduction model, nodes of Ranvier and all that, and that myelin lets electrical signals "jump". What does not add up to me entirely is what the myelin sheath insulates ...
2
votes
1answer
38 views

What does microglia process length tell us?

I'm reading a study investigating traumatic brain injury and alcohol consumption and the researchers measured microglia process length as an indicator of brain damage. I was wondering what that would ...
3
votes
1answer
32 views

A question concerning the strength of synapses

Synaptic strength can be defined »as the average amount of current or voltage excursion produced in the postsynaptic neuron by an action potential in the presynaptic neuron« Synaptic strengths and ...
1
vote
0answers
31 views

Are there nuclei with “real” interneurons?

In Kandel's "Principles of Neural Sciences" in the chapter about the anatomical organization of the brain one reads (p. 323, 4th ed.): »Although a variety of [relay] neurons are involved at each ...
2
votes
0answers
25 views

How sharp are the borders between Brodmann areas?

How does the border between two Brodmann areas look like in Nissl stains? How large is the transition zone where one cannot tell to which of the two areas a neuron belongs to? How many neurons are ...
1
vote
2answers
1k views

What is synaptic clearance?

Please explain what the term synaptic clearance means. For example, what would dopamine synaptic clearance be? It is important to me in context of dopamine signaling variation due to difference in ...
0
votes
0answers
48 views

Long-term potentiations that last for a lifetime

One reads more often than not that long-term potentiation has been reported to last for as long as several weeks LTP is persistent, lasting from several minutes to many months and most sources seem ...
0
votes
0answers
22 views

Which role do dendritic spikes play in long-term potentation?

In the Wikipedia article on long-term potentiation one reads: »When weak stimuli are applied to many pathways that converge on a single patch of postsynaptic membrane, the individual postsynaptic ...
0
votes
0answers
21 views

Normal surplus of neurotransmitters and the need for retrograde signaling

Having learned something about retrograde signaling I wonder why it is so hard to observe and to decide whether presynaptic potentiation actually takes place in the course of long term potentiation (...
1
vote
1answer
148 views

Differences between neurotransmitters and neuromodulators

According to the Wikipedia article on neuromodulation a neuromodulator can be conceptualized as a neurotransmitter that is not reabsorbed by the pre-synaptic neuron or broken down into a ...
3
votes
1answer
55 views

Ion-gated ion channels

Today I've heard for the first time of calcium-gated ion channels but find it hard to get an idea how they work, where they are located, and which role they play. I assume calcium-gated ion channels ...
8
votes
1answer
11k views

How precisely can we sense temperature differences?

We have thermoreceptors, thus we can sense temperature (both warm and cold). I'm interested in the sensitivity of our thermoreceptors - What is the smallest temperature difference that we can sense? ...
2
votes
1answer
45 views

To what extent does loss of neurons in the substantia nigra affect movement?

There is a substance known as MPTP that is capable of crossing the blood-brain barrier. Once it does so, it is metabolized into a toxin called MPP+, which then selectively destroys dopaminergic ...
0
votes
0answers
16 views

Typical firing patterns of neurons in the default mode network in resting state

Inspired by the Wikipedia article on the default mode network where I read: Hans Berger, the inventor of the electroencephalogram, was the first to propose the idea that the brain is constantly ...
2
votes
2answers
54 views

How are presynaptic burst firing signals transmitted post-synaptically?

Neurons can exhibit burst firing and this presynaptic process basically results in a flurry of action potentials being fired in a short time window. I'm, however, wondering how these signals are ...
0
votes
0answers
17 views

Functional roles of firing patterns

Eugene Izhikevich reports – e.g. here – a plethora of neural firing patterns: My question is two-fold: Is there an overview which types of neurons are capable of (and typically exhibit) ...

1
2 3 4 5
10