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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1answer
26 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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795 views

Does variation in human gut length vary predictably with diet of ancestors?

Background: Numerous online searches, textbooks and other sources seem to pin the average length of the human gut from mouth to anus (oroanal) between about 5-10m in length. To pick a reputable ...
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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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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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23 views

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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556 views

Are there neuron mediated reactions faster than reflexes?

I'm interested in how fast the human body can respond to a stimulus. I know the fastest reflex, the blink reflex, operates around 100ms from stimulus to reaction. I also know that the blink reflex ...
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8 views

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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Are 'homeothermic' and 'endothermic' synonymous?

I got this question from the comments below this answer. So, do homeothermic and poikilothermic have the same meaning as endothermic and ectothermic, respectively? A user also suggested that the ...
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1answer
60 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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Wim Hof Method claims Alkaline Blood is Good. Contradictions? Counterproof?

The Wim Hof Method claims, that it is beneficial to have alkaline blood. On the other site there is the medical claim that if the pH-value is not within the range of 7.36 – 7.42, enzyms are ...
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How can heart disease cause excessive sweating?

According to google: What can cause sudden sweating? Excessive Sweating. A person with excessive sweating has a condition called hyperhidrosis. ... In adults, the most common cause of ...
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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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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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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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1answer
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Do human anal glands have any function?

Anal glands in all kinds of animals play a range of diverse functions - providing fat for preening feathers or waterproofing fur, generating distinct scent, even repelling predators. None of the ...
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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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18 views

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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24 views

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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1answer
82 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
45 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 maximum altitude where humans can survive?

What is the highest altitude that a human can survive without being pressurized? Let's assume that oxygen and heat/insulation are not the limiting factors? Why I asked.
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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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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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8k views

Can food swallowed when a person is upside down reach the stomach?

If a person positions him/herself upside down and swallows food, will it reach the stomach against gravity? If so how?
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1answer
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Is it possible to have sleep paralysis while sleepwalking?

At least from a conceptual level, these two disorders don't conflict. The effect of sleep paralysis is being conscious while having the inability to consciously direct motor functions. Sleepwalking is ...
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37 views

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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1answer
26 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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49 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
54 views

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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Is hypoxia/anoxia the ultimate cause of death?

I know there are different causes of death for humans like heart disease, cancer, stroke, injury and so on, but i was thinking if in every case in the last instance death is due to hypoxia/anoxia. ...
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23 views

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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1answer
61 views

Why doesn't patients with chronic acne's body lower sebum production itself? [closed]

Background My cousin has had nodular acne for at least 9 years. Her sebum plugs usually causes bumps on, and inflame, the skin, before the sebum emerges or can be extracted with a comedo extractor. ...
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23 views

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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2answers
218 views

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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1answer
2k views

What is the function of the Hyoepiglottic ligament?

The hyoepiglottic ligament (ligamentum hyoepiglotticum) is an elastic band that connects the epiglottis to the hyoid bone. Although I can find information about the clinical significance of this ...
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15 views

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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1answer
152 views

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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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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2answers
230 views

Why is the resting membrane potential of excitable tissue not affected by the extracellular sodium concentration?

I know that the resting membrane potential for excitable tissue (eg, nerve) is primarily determined by the electronegative difference between the inside and the outside of the membrane for potassium ...
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1answer
2k views

What is the difference between Amino acids from blood and urine?

I would like to understand the difference between different tests for Amino Acids. Any blood laboratory offers amino acids tests using 3-4 methods Blood serum Urine Random Urine 24 hour (all the ...
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124 views

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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270 views

Sex and human's sexual urge.

Why is it necessary for humans to feel pleasure while having sex? Why is it that other animals don't need to experience it? Is it evolutionary ? Why do we mate for pleasure when it's so energy wasting/...
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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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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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