Questions tagged [human-physiology]

For questions on the biochemical, physical, and mechanical functioning of humans in good health including their organs and cells.

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What happens when a human ingests a large meal, and after a short time follows it up with a large amount of indigestible carbs?

A human eats a large meal and indigestible carbs (IC) with such a timing that the IC arrive to the small intestine when it is already full and busy breaking down and absorbing the meal. What would ...
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pH on skin penetration of salicylic acid

I have found that at lower pH, there is more free salicylic acid (due to pKa of roughly 3), which is neutral/uncharged and then can penetrate the skin's oils which are non-polar. At higher pH, more ...
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Studying aging in humans (must be done in “real time”?)

I am asking this general question for members who are knowledgable about human aging research (especially at the molecular level). My assumption is that to study aging in humans directly would require ...
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What is the relevance of the constant in the clearance equation?

I have seen the equation for drug half lives described variously as (0.7xVd)/Cl, (0.693xVd)/Cl, and (ln2xVd)/Cl. What is the origin of this numerical constant in the numerator? What does it signify?
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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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Was there a time in Earth's history when some animal life existed on land but humans could not have breathed?

I understand that higher oxygen content allowed insects and arachnids to grow much larger than today and I wonder if this additional oxygen would have been toxic or unhealthy for modern humans?
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Is there a nomenclature for human physiology?

Back when I studied botany in high school, the teacher taught us the nomenclature for botanical terms. I think there should be something similar for human physiology. Understanding how the name was ...
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Why is glomerular filtration called a non selective process?

According to Biology NCERT Class 11, Page 299, "Filtration is a non-selective process performed by the glomerulus using the glomerular capillary blood pressure." But the glomerulus filters out blood ...
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How does energy conversion happen (chemical to mechanical?) in moving body muscles?

From my understanding, the brain sends electrical pulses through neurons to different part of the body to initiate a movement. My question is, how is the movement realized? For example, in a train, ...
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Would DMSO Be An Effective Solvent For Creating A Transdermal Absorption of NMN + Pterostilbene + TMG In Humans?

I've read conflicting information on this. If not DMSO, is there a better solvent to use?
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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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How does the descending branch of the loop of Henle equilibrate concentration?

I'm learning physiology and I have a hard time figuring out how the cortico-papillary gradient is created. Most explanations go as follow: 1) Sodium is pumped out the ascending branch into the ...
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Adipose Cellularity and Energy Intake

Is it plausible to consider increasing adipocyte size as a causal factor predicting less energy intake in humans in conditions of energy balance. It is well known that higher fat mass (FM) predicts ...
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Why are human wastes yellow?

Except for the feces, which is more brownish, all the human wastes (urine, earwax, snivel, phlegm, and rheum) are usually yellowish. Why is that? I heard that urine is yellow due to bilirubin(?). What ...
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How much does capillary action contribute to blood flow to the human brain?

The BBC News Universal Wonders short video Why water is one of the weirdest things in the universe says after 01:50: Water molecules can float upwards against ...
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What is the effect of lesion of dorsal nerve root?

Dorsal nerve root or dorsal horn of the spinal cord is sensory in nature. The primary afferent neuron or secondary afferent neuron ascend via the dorsal horn of the spinal cord to form the reflex arc ...
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Jungle blindness?

Can people who live in green scenic areas like a jungle be more exposed to green light causing them to not be able to perceive green light as well as someone who may live in a desert void of color? ...
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Sexual Reproduction in Humans

Is the human egg cell (ova) considered motile? We know that is is not actively motile but it is transferred via the fallopian tube to the uterus. Does that make it motile?
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Partial muscle fibre contraction

I'm being taught that: a muscle fibre spans the entire length of the muscle, from the originating tendon to the inserting tendon. The question is, can a muscle fibre contract only partially? Say, if ...
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Using EMG to measure increases in strength

I have a DIY EMG kit and I know it can be used to measure muscle activation. I am wondering, is there a relationship between muscle strength and the value obtained from the EMG sensors measuring on ...
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What adaptations does the human body have to handle frequent and sustained changes in orientation?

Most animals are horizontal with the ground. When they lie down, they get closer to the ground, but their orientation does not change. Humans, on the other hand, stand up straight and tall, ...
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RE: Fasting gastric pH vs Normal gastric pH

If fasting gastric pH values are more acidic then why is it recommended to eat no more than three hours before bed time to prevent reflux. It seems at some point during sleep the stomach would become ...
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Biochemistry of pleasure of/desire for physical exercise in mammalians and humans?

Are there some known biochemical mechanisms, that induces desire for/pleasure of physical exercise in mammalians and humans? I have heard, that horses can not live without physical exercise and they ...
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ATP and Muscle Contraction

I have a question regarding how molecular interactions manifest in physical actions - such as hanging from a bar. To the best of my understanding, when it comes to the contraction of muscles, ATP is ...
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For how long can the heart be in asystole and then restart itself?

The medication Adenosine is used for the treatment of some abnormal heart rhythms. However, according to Wikipedia, it can cause asystole for a few seconds: Because of the effects of adenosine on ...
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Do tendons thickened due to a tendon injury/pathology have the same strength as “normal” tendons?

I read in this 2015 study {1}: This study is the first to show that pathological tendons have sufficient levels of aligned fibrillar structure. Pathological tendons may compensate for areas of ...
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How do painkillers prevent shock?

I was reading about the Placebo effect and came across this little story: The roots of the placebo problem can be traced to a lie told by an Army nurse during World War II as Allied forces ...
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Passing out from drowning [closed]

How long does it take to pass out from oxygen deprivation? The person is panicked and screaming so they accidentally breathe water into the lungs. So how long would it take for them to pass out? After ...
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Sleeping Pill Overdose

How does an overdose of sleeping pills kill? What are the body's reactions to an overdose? In an article published in ScienceDaily, I read that "Sleeping pills owe half their benefit to the placebo ...
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131 views

What is the significance of different types of papillae present on tongue?

Fungiform, Circumvallate, Filiform, Foliate Papillae are present on the surface of the tongue. They have a role in increasing surface area for taste buds that can be accommodated on the tongue. Each ...
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324 views

Why does histamine cause bronchoconstriction?

What purpose does histamine-caused constriction serve in lungs during allergies and such, since it's vasodilator in other parts of body. Wouldn't it be more practical to vasodilate lungs so that white ...
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How are testosterone levels distributed among men and women?

Wikipedia tells me that men have 7 to 8 time higher levels of testosterone than women, on average. Since the hormone is linked with performance in certain athletic events, my hypothesis, which I ...
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Is it impossible to increase skeletal bone mass, as opposed to just bone density? [closed]

I've heard exercise and resistance/strength training increases the density, but doesn't increase mass. So basically, experimentally or theoretically possible at least, can modern science do this/is it ...
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112 views

After how many hours water drunk is expelled from the body?

If one drinks a liter of water at 7 am when (in what span) will that water be eliminated through uresis? Is that process influenced by any factors such as empty stomach, sleep or other?
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Coronary circulation

It is said that the coronary artery that gives the posterior descending artery(PDA) determines if the heart is right dominant(most cases) or left dominant. Is there any reason to this? Why PDA?
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Can disorders involving involuntary muscle twitches and spasms have a hypertrophic and increased residual muscle tension effect?

Meaning disorders specifically like myokymia, myoclonus (positive and negative) and fasciculations. From the section of the literature I've seen, sometimes passing mentions are made when the disorder ...
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Why different people have different Sympathetic reaction

We all know that sympathetic mechanism is similiar in humans . Why people react differently for example one may ran after seeing a lion while other may keep standing or may shout without escaping ?
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Is it correct that the nicotinic acetylcholine receptor has nothing to do with Dopamin?

As I know Dopamine is almost exclusively produced via metabotropic receptors, is it possible for a nicotinic ACH receptor to influence a dopamineric neuron? Can a nicotinic ACH receptor cause a ...
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Can motor neurons in the brain stem start movements?

Supposedly (consciouss) movement is started in the cerebral cortex. But some time ago I've read a research which stated it might be possible some movements (not specified which ones, probably mean ...
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Does every protein starts with Methionine amino acid [duplicate]

During process of protein synthesis we need AUG Codon to start translation .As we know this codon codes for Methionine amino acid so can we say that every protein starts with Methionine amino acid ?
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Why clotting does not occur during Menstruation

As we know when we get injured our body's clotting systems stop the bleeding. So why does it take days for menstruation to stop ?
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In oscillometric blood pressure measurement, why do we assume that highest oscillations correspond with mean arterial pressure?

As far as I've seen, the point on the oscillometric curve where there are greatest oscillations represents the mean arterial pressure (MAP). My question is - why? What is the logic behind this ...
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Sulforaphane vs. Hyperthermic conditioning (sauna use) which would induce a greater heat shock response in the human body?

I’m curious to know which would induce a greater upregulation of heat shock proteins, consuming sulforaphane or putting the body through heat stress such as using the sauna. Sulforaphane reference- ...
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Is it possible for human beings to feed through the nose?

There is a prediction on a futurology site that food can be eaten by inhalation https://2050.earth/predictions/smell-can-feed-you Although aerosol foods do exist they are still eaten by the mouth. ...
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When does the brain stem appear in humans?

This article states: Once the neural tube closes, at around week 6 or week 7 of pregnancy, it curves and bulges into three sections, commonly known as the forebrain, midbrain and hindbrain. ...
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How is fructose absorbed into the body

I’m finding contradicting methods of Fructose transfer to blood page no 264(10)One of which saYs fructose is absorbed by simple diffusion And another sources like this say that fructose is ...
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Why is urea not converted to ammonia in the body?

After the liver processes metabolites to produce urea and other by-products, these travel in the blood to the heart, then they are oxygenated, and some travel through the renal artery to the kidneys. ...
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Pulse Oximetry, what significance does a decimal place hold?

I work in a sleep research lab. We have a couple of Masimo pulse oximeters that report pulse oximetry values in terms of integers (e.g. 90, 91, 92, etc.). Now our principle investigators used to use ...
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Sensory-motor pathway from visceral organs

Does anyone know is which nerves carries the transmission of sensory-motor impulses from the visceral organs? Is it splanchnic nerves? There is conflicting evidence in the literature. On the one hand, ...
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Why do children not have the Acid Mantle?

Post puberty humans begin to secrete a substance called Sebum which changes the neutral PH of our skin from ~7 to 4.5-5.5. This has that advantage of serving as a protective line against pathogens and ...