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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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Contracting mouth muscles as reaction to taking in specific food items

When eating very specific food items, especially confectionery like (salty) liquorice, (it feels as if) the muscles of my mouth contract, right when it hits my tongue. Does anyone know why this ...
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Can the heart generate its own rhythm independent to the SAN?

My textbook and a revision guide, which I believe is a reinterpretation of the textbook, state that: The SAN initiates waves of excitation that usually override the myogenic action of the cardiac ...
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human sight at 1000x while looking into the mirror

I noticed that my eyeballs have the ability to see in what appears to be 1000x. Setting the conditions: Look into a mirror while in a well lit room. (for me the lighting in my living room as opposed ...
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Can the mandible in humans be rotated without surgery?

Can things like mewing, chewing or face pulling affect the angle of the mandible in humans? By "angle" I mean the precise angle between the gonion of the ramus down the mandibular body to the chin -- ...
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1answer
23 views

Effect of the same caloric intake of different macronutrients on body weight

To gain weight, caloric intake > caloric expenditure. To lose weight, caloric intake < caloric expenditure. But what is the effect of the type of macronutrient ? That is to say : does the same ...
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65 views

Why do our bodies maintain blood pressure but not the flow rate?

This might be a silly question but i'm not not clear I'm always told that blood pressure is homeostatic parameter and can't not be changed but isn't what important is the flow rate to the organs? ...
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58 views

Where would vegetarians/vegans get a substitute of hemo/myoglobin from?

As far as I understand, there is a difference in the iron absorbed from meat than from other sources like grains and vegetables. If this is the case, is it possible that not ingesting the hemoglobin ...
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why is BMI computed from mass and surface instead of mass and volume

Surface area of cube with size $a$ is multiple of $a^2$. The same holds for balls and any three dimensional object. Volume of cube is $a^3$. Volume of ball and other three dimensional object is ...
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How is counter current set up in a newborn baby

I was reading about the kidney and to be more specific,counter current mechanism in kidneys.Now the thing is that there is varying concentration gradient in kidney from cortex to medulla in a nephron....
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Do the normal in vivo spatial growth controls, not apply to hair follicles?

The common changes in hair growth are linked to changes in the size enlarging anagen follicles achieve. According to the accepted science in tissue physiology, the in vivo growth of the anagen ...
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Which major salivary gland secretes maximum amount of salivary amylase and which one secretes maximum amount of Saliva

Actually I was studying about digestion and got this confusion about which gland(Parotid or Sub-mandibulary) secretes maximum amount of saliva and which one maximum amount of Salivary Amylase. Also,...
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Increase Cysteine levels in melanocytes

I wonder if cysteine could be of use in the development of safe skin lightening agents as opposed to the many unsafe methods in use. As can be seen in the following diagram melanogenesis divides after ...
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Human Body Electricity

Since the human body has electricity, can the human body use that energy in any possible way? Such as using it to power something in any way. As you know we can use technology because we have ...
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Is there any evidence that Vitamin K-2 megadoses increase bicondylar, bizygomatic or bitemporal breadth in humans?

Can megadosing or supraphysiological dosing of Vitamin K2 (MK4; Menatetrenone) over prolonged periods of time cause an adult's bicondylar breadth, bizygomatic breadth or bitemporal breadth to grow ...
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How is the “sampling time” of the human visual system influenced by things like hormones, metabolism, or our circadian rhythm?

For example people experience time passing slower when they are in a adrenalin rush. What is the mechanism behind it, and where can I read more about it ?
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Plasmatic anion gap or chloremia?

Since high anion gap metabolic acidosis is characterized by normal blood chloride levels and normal anion gap metabolic acidosis is characterized by elevated blood chloride levels, why it is necessary ...
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35 views

High altitude rail travel

This question is primarily about human performance. I do know about hypoxia, hence this question. I'm busy designing a fictional region, currently in the 1930's. I have a railway line that climbs to ...
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What is the optimal time to implant embryo in uterus for in vitro fertilization?

What is the best time to implant an embryo in the uterus. I was under the impression that the earlier the better and more natural, but also if you wait until the blastocyst age, it may be better to ...
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53 views

Do fat people have more chances of developing nitrogen bends?

I was reading some text on deep sea physiology. I got to know that solubility of nitrogen in fat is five times that in water. The exact text from the book animal physiology adaptation and environment ...
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39 views

Actual definition of cardiac output

Is cardiac output the amount of blood pumped by both ventricles in 1 minute or only by the left ventricle in 1 minute?
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45 views

What are the effects of oxygen toxicity in human blood?

I was reading some text on deep sea Physiology, and for to know that diving to do could cause oxygen toxicity in the blood. This was the exact text from the book Textbook of Medical Physiology by ...
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1answer
38 views

What type of movement is “spontaneous movement” if it isnt reflex movement and it isnt purposive movement?

According to Spontaneous and induced fetal activity Spontaneous motor activity of the foetus depends significantly ot the foetal age; during the period between the 12th and 16th week it was ...
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55 views

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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2answers
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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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1answer
38 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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49 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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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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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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179 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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1answer
33 views

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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41 views

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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141 views

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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1answer
240 views

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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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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424 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
92 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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264 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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55 views

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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54 views

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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1answer
31 views

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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58 views

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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381 views

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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147 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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86 views

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 ...