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 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 ...
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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 ...
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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?
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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 ...
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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 ...
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How Beta-endorphine affects mood (mechanism of action)

I am finding hard to locate mechanisms (involving neurotransmitters, hormones, receptors, proteins) that explain why beta-endorphins (and endorphins in general) make us "feel good" (euphoria sensation)...
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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 – ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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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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 ...
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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 ...
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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 ...
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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., ...
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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 ...
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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. ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 (...
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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 ...
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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 ...
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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 ...
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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) ...
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Neuron stimulation experiments

Has anyone extracted a class of neurons (or a connected set of neurons) and stimulated them electrically to get an understanding of their behavior? If so, could someone point me to papers along these ...
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Vision: what is the difference between on-off ganglion cells and lateral inhibition?

Is 'lateral inhibition' just a term for the biological basis of the functioning of the on-center (or off-center) ganglion cells? Or do these terms describe separate processes?
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Is it possible to simulate tetrachromatic vision in a trichromat?

Suppose we are able to stimulate the whole matrix of cones of a human retina, targeting each cone individually¹. Normally we would project an image in the LMS color space onto the cones, in such a way ...
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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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What is the role of increased cytosolic calcium concentration after firing, in neuronal cell bodies?

I've come across several studies in which scientists were investigating various questions related to neural activity by focusing on neuronal cell bodies using Calcium imaging. As this article suggests ...
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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 ...
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Can brain activity be restored after being stopped, assuming no cellular damage?

I was reading about cryonic preservation recently. In a separate place on the Internet, I've read that once brain activity stops and brain death occurs, the person is dead with no hope of recovery. ...
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Reference Request: Human visual system takes in $10^7$ bits/sec at the periphery and compresses it down to 50 bits/sec deep inside

In Sparse Components of Images and Optimal Atomic Decompositions by Donoho, 1998, the author claims that The human visual system is thought to do a tremendous job in achieving sparse ...
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Functional unit

What is meant by functional unit of a system? like when we say that the neuron is the basic unit of neural system do we mean that all those things that are performed by neural system can be performed ...
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Why/how does exposure to noise cause cochlear hair-cell loss?

I am trying to understand why listening to loud music - e.g. concerts or earphones at high volume damages hearing. According to the National Institute on Deafness the cause is physical. Most ...
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What is the purpose of descending auditory signals from the brain?

What might the purpose be of the brain having descending auditory signals from the brain? My textbook is very vague about this and I am just curious.
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By what mechanism do our nerves lengthen as people get taller?

How do nerves get longer as kids grow taller? I searched for an answer but I can only find information on the formation of nerves in embryos.
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Do astrocytes connect and chemically communicate with other astrocytes?

I am building a novel model of neural tissue for the purposes of Machine Learning and am currently trying to unpick the functions of the astroglia. The literature suggests that astrocytes ensheath ...
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What makes synapses stay “fixed”?

What makes synapses not move or pre- and postsynaptic cells neither touch nor move away from each other? I mean the synaptic cleft is a gap between the pre- and postsynaptic cells that is about 20 nm ...
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can auditory/ocular reflexes exist?

In the same way the knee-jerk reflex is a thing (I think the nerve signal doesn't go through the brain?), can stimuli received by the eyes or ears trigger "instantaneous" (faster than the brain can ...
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Can we “learn” reflexes?

Can we force our bodies to react to situations faster than our brain can think about them? Some reflexes I can think of off the top of my head: knee jerk reflex retracting hand when touching a hot ...
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Are cold weather tolerance and spicy food tolerance related physiologically?

If a person grew up in a cold place they happily walk outside in winter in short sleeves and shorts in places with mild Winters while the locals are bundled up in thick jackets. Spicy food with ...
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Cerebral/Cerebellar Cortex versus Deep Nuclei

I have troubles using the terms Cortex & Deep Nuclei, and 'Nuclei' in general. From what I understand, a brain has '3 matter types in accordance to anatomical locations' Superficial Grey matter - ...
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Can humans ever directly see a few photons at a time? Can a human see a single photon?

I am not asking the following question: Can humans ever see a photon in the same way we see a chair? My question is: Can a human retina respond to a single photon? If so, how does this happen and why ...

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