This tag is for questions about the general biological features of human beings (as opposed to the biology of non-humans).

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1answer
95 views

Is there a known glucosepane cross-link breaker?

I read the following on wikipedia: There is, however, no agent known that can break down the most common AGE, glucosepane, which appears 10 to 1,000 times more common in human tissue than any ...
2
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1answer
28 views

Are there any generic (not dependent on symptoms) ways to find parasite infections?

Are there any generic ways to determine if a person is infected with a parasite? With "generic ways" I mean ways that do not rely on symptoms caused by a particular parasite. Also I am mainly ...
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1answer
53 views

Pituitary giants - is the fusing of growth plates dependent on amount of growth hormone in blood?

I wanted to ask a couple questions related to pituitary giants (people who are giants because of some anomaly, such as a tumor, in their pituitary gland). Some of these giants seem to keep growing ...
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1answer
42 views

How can succinylcholine cause myorelaxation?

I first thought that this is because of prolonged depolarisations. However, I am not sure anymore, because after reading PubChem, the only possible pathways are are Choline agonist. So I would say ...
2
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1answer
4k views

Why can't ciliary muscles in the human eye relax like other muscles?

I had laser eye surgery a decade ago, but in recent years my eyesight has become significantly myopic. I consulted an ophthalmologist to see if this was eye strain because I work at computers a lot, ...
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1answer
36 views

What is the biological basis for tiredness after eating? [duplicate]

I can sometimes feel quite drowsy after some "meals" (e.g. a cold cut & cheese sandwich with juice on the side) and less drowsy (or maybe less often) after others (such as a salad). This ...
6
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1answer
85 views

Is the eyes' movement discrete?

When tired and it was dark, I noticed that if I focused on a dim light source and moved my eyes fairly rapidly sideways, the resulting images that lingered for a short while were not smoothly blurred ...
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2answers
106 views

What triggers programmed cell death in humans (from outside the cell)?

What triggers programmed cell death in humans? Is it decided by the brain (for the entire body)? Or is it a local decision of a cell by its environment? Something else? I realize that there might be ...
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1answer
1k views

What's the minimum distance of focus for the lens of a human eye to reach maximum flatness?

According to the Wikipedia article on eye accomodation, the range in which a human eye can focus is from 7 centimetres away up to essentially an infinite distance. Of course, people can't see things ...
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1answer
32 views

Is there any disadvantage to having a really low adipocyte count in our times?

The key feature of adipocytes seems to be energy storage. Today humans in Western countries don't have to hunger and have therefore less need to store energy in fat cells. Do adipocytes have ...
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0answers
22 views

Why after physical activity I see flickering concentric circles? [duplicate]

After prolonged hard physical exercise such as running uphill I sometimes experience rapidly vibrating black-and-white concentric circles for a few minutes, looking like a sinusoidal zone plate, small ...
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1answer
51 views

Is it true that some organs “sleep” at certain times of the day and does this affect dieting or when to take medicine?

Is it true that some organs (such as the liver or the intestines) are less active at certain times of the day, regardless of whether the individual is awake or not?
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2answers
313 views

What effect does the Barr body have, in relation to female Turner syndrome?

Why do persons with Turner syndrome have developmental abnormalities, when normal XX-females do not, even though they only have 1 active X chromosome? From what I know, one X-chromosome is ...
0
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1answer
56 views

How much of the human body is processed sunlight?

So I believe (and correct me if I'm wrong--it's logic, not research) that the human body is pretty much all just processed sunlight based on the food chain. How much, if any, of the human body is ...
8
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2answers
179 views

What is the human ear's temporal resolution?

What is the smallest sound duration that the human can hear? In other words, what is the lower duration limit for a sound to be translated into electrical signals by the ear? Suppose the human ear ...
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0answers
23 views

Is this description of etiology of celiac disease correct?

There is a detailed and, to my inexpert eyes, plausible description of the etiology of celiac disease and other autoimmune disorders posted here: http://no-gluten.org/CeliacDisease.htm Is it is at ...
3
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2answers
103 views

Why can't we defibrillate the heart within 1 minute after ventricular fibrillation by electroshock?

We mostly can defibrillate the heart before 1 min of ventricular fibrillation by electroshock.Then we often can't do defibrillate it with electroshock. What's the reason and What's the best way to ...
3
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1answer
45 views

Why do the size of the phase 1 notch vary among cardiac cells?

The size of the phase 1 notch varies among cardiac cells. It is prominent in myocytes in the epicardial and midmyocardial regions of the left ventricular wall and in ventricular Purkinje fibers. ...
2
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1answer
115 views

Why do ion concentrations change with different secretion rates in pancreatic juice?

Why is it that when secretory rate increases in the pancreas the concentration of chloride ions decreases, and the concentration of bicarbonate increases in the production of isotonic NaCl secretion? ...
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3answers
5k views

Can one die from pain?

Is it possible that a human or any other creature can die from pain? I googled and found different answers. Some articles say Yes while others say No.
9
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1answer
225 views

Why doesn't HDL cause diseases like LDL? [duplicate]

LDL particles pose a risk for cardiovascular disease when they invade the endothelium and become oxidized, since the oxidized forms are more easily retained by the proteoglycans. A complex set of ...
0
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1answer
70 views

Safety of cobalt-chromium and nickel-chromium dental implants

How safe are cobalt-chromium and nickel-chromium alloys used in dental implants (porcelain fused metal)? IARC groups nickel and cobalt metals in group 2B and chromium in group 3 (hexavalent chromium ...
8
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2answers
180 views

Why don't we see turbulence in the aorta even in normal situations?

I read about the Windkessel effect. Then I read about pulse pressure waves getting reflected from the periphery. If the pulse pressure wave is reflected during diastole and at the same time blood is ...
5
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1answer
187 views

Is a raised baseline between T and QRS normal in any ECG lead?

Here are excerpts from an unknown ECG lead. I find it weird that the "baseline" changes after the T wave and doesn't return until after the following QRS complex. Is that normal/expected for any lead? ...
4
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1answer
82 views

Circulating factors affecting human health/longevity

Circulating factors present in young mice have been shown to promote rejuvenation of aged mice, suggesting that tissues have inherent capabilities to regenerate, and circulating factors may be ...
6
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1answer
951 views

Is it biologically possible for an adult's eye color to change?

Can it be that the adult eye can change color? Specifically my question is about a unilateral color change, such that the color of one eye remains constant, while the other changes color over time. ...
3
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1answer
152 views

Why does our voice change when we get affected by cold or cough?

Why does our voice change when we get affected by cold or cough? I observed the voice change thing in so many people including me.
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1answer
196 views

What's the smallest size a human eye can see?

During a biology experiment at school, where we would look at waterweeds under a microscope, my teacher said something about that it's impossible for the human eye to see the cells without a ...
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1answer
58 views

Does repolarization of muscle fibers mean that the muscle bundle is relaxed?

If I flex my bicep and continue to contract it does it mean that the muscle cells are in depolarizing state and not repolarizing?
7
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1answer
95 views

Can humans live without their right atrium?

The right atrium is one of four chambers (two atria and two ventricles) in the hearts of mammals (including humans) and archosaurs (which include birds and crocodilians). It receives deoxygenated ...
7
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2answers
203 views

Why do we have more male infant born?

For every 104 male babies,we have 100 female babies and there is a Statistics which is more reliable (we have 997 female infant born per 1000 male infant born). what's the reason? why do we have male ...
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0answers
34 views

Why does human hair grow and behave differently depending on its location?

Why does human hair behave differently depending on its location? For instance, head hair grows to an indefinite length, but eyebrows maintain a particular length and appearance. Head hair and ...
12
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4answers
2k views

If body temperature is 37°C (98.6°F), why are most people more comfortable at around 21°C (70°F)?

It may be different for other people, but for me, anything above 32°C (90°F) is very uncomfortable, and my body is inclined to seek cooler temperatures. But I would think that at 32°C, the body would ...
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4answers
72k views

What's the maximum and minimum temperature a human can survive?

This is a question that has been in my mind since I was a kid. I'm not a doctor, nor even a biology student, just a curious person. What is the minimum and maximum temperature a human body can stand ...
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2answers
159 views

What is atrial fibrillation? [closed]

I am wondering exactly what a-fib is (causes and symptoms). I would really appreciate having a sample of an EKG with it (because in my limited research, I have found it nearly impossible to find just ...
12
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3answers
2k views

Why does hair grow after trimming but remains at a constant length after a while?

Some hair especially body hair regrows after trimming but stops growing after a while. What is the mechanism behind control of hair growth and how is the length limit determined?
5
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1answer
101 views

Is there any scientific evidence that a human has ever grown a third set of teeth?

This is about the possibility (or lack thereof) for a person to re-grow a new "permanent tooth" or set of teeth, to replace the teeth that grew after their milk teeth fell out. I had earlier seen ...
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0answers
15 views

Retinal eccentricity to colour sensitivity [duplicate]

Colour perception goes out to 50 degrees but is the sensitivity to RGB. Question is it the same in the four quadrants of the retinal field? That is if the red colour sensitivity eg is 30 temporal ...
5
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1answer
104 views

What's the worst that can happen from too much sleep deprivation? Can you die?

It is well known that sleep deprivation causes considerable discomfort in humans (and has even used as a form of torture), but nevertheless there have been people who went through protracted sleep ...
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0answers
32 views

If what we eat can be seen in our hair, then to what degree can our food affect the “look and feel” of our hair?

It looks like most things (or everything?) that we consume, whether it is a food, drink, or something we smoke (like e.g. some drug like marijuana) ends up in some amounts in our hair. If this is the ...
0
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1answer
38 views

How is oxygen and carbon dioxide exchange mediated by hemoglobin? [closed]

Oxygen is transferred by hemoglobin from the lungs to tissues, while carbon dioxide is transferred by hemoglobin from tissues to lungs. How is this regulated bidirectional transfer mediated?
3
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1answer
887 views

Why does the stomach ache if you take a brisk walk after lunch or dinner

After eating your lunch or dinner, if you take a brisk walk, most of the time your stomach aches. Why does that happen? What happens with respect to the body metabolism?
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2answers
228 views

What do biologists mean when they use the term “biological distance”?

Here is its usage. "there is sufficient genetic control to make nonmetric traits useful in anthropological work, and such variables have successfully assigned individuals from distinct geographic ...
4
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1answer
76 views

Does transplanted heart have full sympaticus without medication?

I am reading this and this where I am considering this sentence [N]o baseline parasympathetic innervation [in transplanted heart]. Does this sentence imply that the heart work then in full ...
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2answers
64 views

Does the cellular response to every receptor work the same way?

I heard somewhere that activating any receptor results in the same intracellular response (signaling) which involves NF-κB. If that is true, I hardly understand how the cells distinguish between ...
2
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2answers
62 views

How do humans perceive time?

We can see length, and other physical quantities. We can perceive through our other senses like (temperature through thermoreceptors, weight through pressure receptors etc.). But how do we "sense" ...
2
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1answer
44 views

How does the genetic material differ between dizygotic twins and ordinary siblings?

I am going to give a rough presentation on twin studies. The terms heritability and concordance are included already, but I struggle with understanding the difference of the genetic material of ...
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0answers
48 views

Why do we have butt hair? [duplicate]

Why do we have hair on our butts? From what I understand, hair is generally used for warmth, but it seems like our buttox would be one of the last places on our body that would need warmth. Moreover, ...
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1answer
449 views

Do the right-handed people tend to use the right side teeth of their jaw to chew food more often than the left-handed people?

And vice versa, do the left-handed people tend to use the left side teeth of their jaw to chew food more often than the right-handed people?Or the frequency of food chewing distribute fairly to both ...
19
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1answer
2k views

Why do we have five fingers?

Humans (and other humanoid mammals) have five fingers in each hand. Curious to know, why five? Wouldn't more fingers be more useful? Is there any evidence that it used to be different and natural ...