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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20 views

Can Future Shock Really Kill? [closed]

A trope I keep running into while researching various things like Artificial Intelligence is the concept of "Future Shock." Essentially, a person from the sufficiently distant past (or a ...
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Are intestinal and pancreatic lipases different?

For explaining the action pancreatic lipase, my book wrote this equation:- $$fat\space particles + lipase\rightarrow fatty\space acid + glycerol + lipase$$ But for intestinal lipase, my book has a ...
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Under which conditions is human energy consumption minimized?

Including but not limited to: body state consumed food composition state of the digestive tract diseases wounds sleep coma, etc.; death excluded environment state temperature light pressure, etc. ...
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31 views

Do pinhole glasses help reduce eye strain?

I've noticed that I can read about 10x longer at screens and books without my eyes tiring using the "pinhole trick" - where you curl your fingers and look through the hole (great explanation here ...
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Why do arteries have a small lumen? [closed]

My biology textbook says that arteries have a small lumen relative to the thickness of their walls. I understand why they need thick walls, to withstand high pressure and stretch etc. But when ...
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Why don't we dribble tears through our nose?

Basal tears are tears produced by the lacrimal gland and they lubricate the eye. They are then funneled into the lacrimal sac and then from there into the nose eventually. If this is the case, why ...
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Why does it take so long to bleed after accidentally cutting yourself?

Sorry if this is not a good site to ask this question, but I recently accidentally cut myself while chopping onions (very minor, no serious harm done), and noticed that it took quite a while before ...
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Which results in greater energy expenditure: consecutive actions, or non-consecutive actions?

Is there a difference in energy expenditure when performing the same set of movements consecutively vs non-consecutively? Example: You jump in-place 1 time, stand motionless for 1 minute, and then ...
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1answer
62 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., ...
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Why and how do red bone marrow concentrations in humans change during traditional aging?

I have found several pictures that suggest this is the case. As for peer reviewed papers I've found plenty of papers hypothesizing and testing as to the why of changes in populations of HSCs, a few ...
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1answer
47 views

Why doesn't copper affect human skin?

It's been known for a long time that copper has antimicrobial properties, but if it is so potent, why does it seem to have no effect on human skin or really any large animal?
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Origins of the body mechanics theory

In physical therapy and occasionally in sports coaching, there's often a precise description of the mechanics of what happens during the movement (which muscles are engaged, which joint moves where ...
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How do precordial leads measure electrical changes in the heart?

In precordial leads the electrodes from limbs are connected to a common point via resistors. What is the potential at the common point?
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What percent of mucle growth is possible without steroids consumption?

I am interested to know, if someone does bodybuilding exercises with good rest, enough protein, high presure workout, etc, but without consuming any steroids, how much of muscle gorwth is possible for ...
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126 views

Why do patients with type 2 diabetes not show the body wasting seen in type 1 diabetics?

Type 1 diabetes results from the destruction of the cells in the pancreas that produce insulin, while type 2 diabetes is characterized by so-called "insulin resistance", presumably a reduced ...
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20 views

What's the function of vitelline circulation in human embryo?

Why do we need a vitelline circulation if we already develop a placenta to gather all the nutrients we need? Is it an evolutionary remain?
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How much blood do we have when the heart first starts to beat?

How much blood do we have when the heart beats for the first time? It should be between the third and fourth week of embryonic life.
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Reflex muscular activity in three months old fetus

At the end of the third month, reflex activity can be evoked in aborted fetuses, indicating muscular activity This quote is from Langman's Medical Embriology. Have I misunderstood it or it is ...
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126 views

Why is arterial pO2 normal in carbon monoxide poisoning?

Arterial blood gas measurements often show that pO2 is 'normal' even though haemoglobin is bound to carbon monoxide with high affinity. Is this because there is still oxygen bound to some subunits of ...
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1answer
59 views

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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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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27 views

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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1answer
58 views

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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56 views

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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1answer
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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 the ...
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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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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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1answer
94 views

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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1answer
182 views

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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99 views

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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546 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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87 views

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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2answers
68 views

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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232 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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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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33 views

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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202 views

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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