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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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How would a human wearing earth clothes die on mars? [duplicate]

Please answer immediately If a astronaut out of her spaceship onto mars without her spacesuit, but just wearing her earth clothes, would she die first from suffocation, boiling fluids, freezing, or ...
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What is meant with “the chest wall and lungs are coupled together”?

Since the lung and chest are elastic, we can represent them with springs. Under normal conditions, they are coupled together: the “lung” springs are stretched and the “chest” springs are compressed. ...
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What does this part mean “ the narrowing part tends to maintain itself”?

When the vessel is narrowed by artherosclerosis, the velocity of the flow increases in the narrowed part and the distending pressure in that part decreases. This means "the narrowing part tends to ...
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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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What is the chemical (element proportions) composition of standard food?

If we take a standard, nutritious diet of a human, and split it into atoms, what will be the typical proportions of the basic constituents: carbon, hydrogen, oxygen? We can ignore all the ...
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35 views

How efficiently does the human body convert the energy stored in fat into kinetic energy?

I read that one gram fat contains 9 kcal energy. There are many tables around claiming that x type of exercise for t duration ...
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1answer
48 views

Is there any evidence of causation for breathing rate to affect blood pressure in a human?

I did some research and trials, and with 5 trials for a normal heart rate and 5 done 45 seconds into breath holding, the results came back showing that my heart rate of 116/65 mmHg increased to 138/90 ...
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34 views

Can some colours be processed faster/more accurately than others?

Is the human visual / motor system able to track, and move in response to, objects of certain colours more quickly and reliably than for others? By more reliably, I mean with greater accuracy in ...
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“Decreased cardiac output and increased water retention stimulates the SNS” Why?

So, in lecture notes created by my university lecturer regarding cardio-thoracic nursing, she has made the statement I have put in the title: Decreased cardiac output and increased water retention ...
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Why do I feel nauseous at the sight of blood, despite not being afraid of it?

Every time I ask google this question, all it spits at me is info on blood phobias ^-^; basically, I've always been hugely interested in morbid stuff, but I noticed that I always feel sick when ...
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134 views

Why does eating saturated fat increase blood cholesterol?

I am interested in the biochemistry of diet and the way we have been advised to eat for the past forty years. In researching an explanation for the relationship between dietary fat and blood ...
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What is the evolutionary advantage of getting hard nipples when being aroused? Why can they even be stimulated sexually?

I try to understand the evolutionary advantages of the body reactions of nipples and penises/vaginas. I'm confused, because I can explain the evolutionary advantage in a logical & consistent way ...
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What is (are) the medium of conduction for an electrical current with an external source in the human body?

I am trying to get some background for some personal research I am doing into the effects of Electro Convulsive Therapy. I don't understand how electric current from an external household source, say, ...
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Is there muscle hyperplasia or hypertrophy after surgery?

After exercise there is hypertrophy only. I am curious, if a surgery removes muscle, will there be hyperplasia or hypertrophy to restore it?
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does being battered build muscle?

My crude understanding of how people normally go about building muscle is something like this following 2 step process: 1) a person can lift weights (for example), which tears muscle and stimulates ...
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Once neurotransmitters bind to its receptors, how does the post synaptic neuron “know” when to start a new action potential?

My textbook seems to gloss over this subject. Once the post-synaptic receptors are activated, do they cause particular ion channels to open, letting positive charge into the cell and inching the ...
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Interstitial volume

In the literature, studies mention that the interstitial space surrounding cells varies in each tissue. Are there references from which one can obtain the values of interstitial volume in each tissue?...
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Why exactly does the immune system weaken with age?

Why does the immune system become weaker with age in humans and in some other mammals? Let's try to be more specific than just "everything degrades with age."
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Why do humans lose subcutaneous fat from the extremities with age?

Why does fat tissue die and shrink on the hands, knees, and lower legs of most people as they age, even when they are overweight? In most people, their bone definition becomes much more visible around ...
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Why do humans lose subcutaneous fat tissue with age?

Why exactly do humans lose subcutaneous fat tissue with age? It appears that we either lose fat cell volume or we might actually be losing the number of fat cells with age. One hypothesis is that as ...
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What is the purpose of chloride ions in the stomach

Why are chloride ions secreted into the gastric pits in addition with hydrogen ions? Why can't the parietal cells simply secrete hydrogen ions for an acidic effect?
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Why do I have super vision in purely red light?

I installed some RGBW led strips in my apartment recently.. by some I mean everything is now lit by led strips and there isn't a single light bulb left. One thing I've noticed over the last few days ...
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How does 2,3 biphosphoglycerate works to release oxygen bound to the hemoglobin?

I read on Wikipedia that 2,3 BPG binds with the deoxygenated state of hemoglobin and helps in stabilizing it. It was also written that it helps release remaining oxygen from the hemoglobin. How? ...
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345 views

Spermatogenesis question

I found this diagram in my textbook regarding the process of spermatogenesis. But, I doubt if the labelling done is correct or not. Especially, I can't figure out any difference between the cells ...
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1answer
89 views

What is the benefit of oxygen tanks to persons trappped in an enclosed space?

When people are enclosed in an air-tight space, the levels of carbon dioxide will rise to lethal levels (hypercapnia) long before the oxygen is exhausted (hypoxia). For example, the astronauts of ...
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256 views

Immune System - B-cell receptors

How do the B-cells, which are a part of our body, develop antibodies against antigens of outside world (outside of our body), which they don't even know about? Is it just a random match?
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Is the serum concentration of calcitriol different at different times in the day?

Given that calcitriol has a relatively short half-life in adults it would be possible that the serum concentration is at different times of the day different if it gets produced in different ...
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Is the heart more relaxed when stretched or contracted, and how does it affect cross-bridge interactions?

In the heart, are stretched muscles during the diastole more relaxed or are the contracted muscles more relaxed? Depending on the answer, are there then more cross-bridge interactions in cardiac ...
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Which components grow in size but not in number and which grow in number but not in size?

During growth of an individual animal some components of the body grow in size but not in number (type 1) while some others increase in number but not in size (type 2). Which of the following is ...
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1answer
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Why does the right bundle branch not have any terminal filaments in the IVS of the human heart?

Dubin's "Rapid Interpretation of EKG's" briefly describes this part of human physiology but doesn't explain the reason behind it. Is there a specific advantage of the human heart having this ...
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How can there not be purpose movement in the fetus until week 18, when a fetus can open its mouth and suck its fingers at week 11?

According to Fetal Movement According to an overview produced by the Royal College of Physicians of Edinburgh, purposive movement begins at about 18 weeks, gradually replacing reflex movements ...
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1answer
93 views

Causes of Back Dimples

What are the causes of the dimples commonly found above the buttocks? They seem to be in line with the sacroiliac joints. Do the joints have anything to do with them?
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1answer
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Do fruit juices have a diuretic effect & what governs this?

Was just contemplating this. Juices tend to contain a lot of sugar. Does the body absorb all the sugar in juices? If the body does not, that sugar must be excreted by the kidneys alongside water ...
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What is the average volume of the human Psychic tear? (“emotional tear”)

My goal is to find out the volume of the average human "emotional tear" (Psychic tear - sadness, happiness), specifically when crying. I found a lot of information about Basal tears (constant ...
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How is it possible to breathe perflurocarbon?

I have heard of liquid breathing, where an organism, usually a person, would be breathing in perflurocarbon. Now I looked up perflourocarbon on wikipedia and I noticed, no oxygen at all, but fluorine ...
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641 views

Ventricular Filling : Systole or Diastole?

As the Blood goes down from the Atrium to the Ventricles: The Tricuspid Valve ( Right Atrioventricular Valve) Bicuspid Valve (Mitral Valve ) The atrial pressure is INCREASES WHEN ATRIA ( THE ATRIA ...
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Is the glomerular filtration rate, per kidney or for both?

We say in a healthy human being the average glomerular filtration rate is about 120 mL/min. Is that for both kidneys together (60+60), or just one kidney? Pardon me if this makes me sound like an ...
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How does the stomach differentiate between liquids and solids to initiate churning?

Or maybe it doesn't at all. Can the stomach tell the difference between liquids and solids and change its churning process accordingly despite that it has no nerves? Because liquids don't need to be ...
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does the amount of blood circulate in a body is same before and after amputation?

if a person loose his hand in an accident do the blood flows through his body is equal to the volume of blood before accident? how human body manage with that blood which is deserved by the missed ...
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How to obtain normalised ECG given ECG readings across lead 1, 2, and 3?

I saw this youtube video on ECG readings and cardiac dipole vector locus of the heart across the three leads. Posting screenshots from it: My question is how to obtain the graph (2nd image) from the ...
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Nonpancreatic digestion of tryglicerides

In an answer about coconut oil I can read the digestion of coconut oil does not involve in the Pancreatic digestive enzyme system In both primary and secondary school I have learned that fat needs ...
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How can diving with 100% oxygen not destroy your lungs? [closed]

It is possible this should be moved to physics, depending on the nature of the answer (i.e. if the reason is physical). But I suspect the explanation is biological, so I posted it here. Sometimes ...
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1answer
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Why doesn't patients with chronic acne's body lower sebum production itself?

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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Are all of our hormones synthesized in the same gland that they are secreted from?

For example, growth hormone is secreted from the anterior pituitary; is it also synthesized there?
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How do (commensal and mutualist) microorganisms colonize the seminal vesicles?

Human's seminal fluid has it's own microbiome (Javurek et al. 2016). How do species of this microbiome (bacteria and eukaryotes) colonize the seminal vesicles? It is possible that different species ...
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What's the ratio of saturated to unsaturated fatty acids in human cell membrane?

It's well established that the fluidity of a cell is largely dependent upon the ratio of saturated to unsaturated fatty acids that exist within the membrane, but, what exactly are the values for this ...
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42 views

Is there gas exchange in the fingers?

I saw A documentary many years ago that said that hemoglobin will take in O2 in the fingers and toes. I have Not been able to find any information on this. But it would seem that being so close to the ...
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How to estimate equivalence units of short-acting insulin in long-acting insulin?

You have a combination insulin therapy for DM2: metformin + two long-acting insulin medications A and B. There is no A in the pharmacy, and you have blood glucose 6 now, for instance (over 5). You ...
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effect of arterial vasocontriction on the pressure in arteries

if experimentally one induces smooth muscle contraction on an artery and cause it to constrict, keeping the cardiac output same and also the arteriolar resistance(total peripheral resistance) the same ...
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Required energy to metabolize fat

Tl;dr: What is the net joule value of fat if used for energy provision, compared to e.g. carbohydrates. So does 1 Joule Fat intake result in 1 - X Joule energy provided to the cell, or does it work in ...