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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3
votes
2answers
51 views

Are nutrients absorbed in human esophagus?

Following this question regarding absorption in human oral cavity (sadly not yet fully answered), I'm curious if any nutrient absorption occurs during the descent of food through the esophagus. And ...
-1
votes
0answers
32 views

What is it a swell in the body? [on hold]

When I get hurt, for example injuries to a bony part causes it to swell...like a little mountain. What is it actually? Does it happen in other places on the body?
4
votes
1answer
48 views

Are some facial features more important than others in human facial recognition?

I'm often surprised by the human ability to correctly identify other individuals despite significant modifications due to ageing, hairstyle, injury etc. But, sometimes the addition of a beard and a ...
8
votes
1answer
2k views

What is the female equivalent of the morning erection that some men experience?

There was question about what causes "morning wood." It was answered that the erection in the morning is caused by decline of norepinephrine during REM sleep. Which in part allows to prevent ...
-1
votes
0answers
25 views

Why Muscle Popups? [on hold]

I am a swimmer, I swim 6 times a week 3 hours every time. After almost every train when I get to absolute rest, my hand muscle popup... and just lately I have noticed that once in a while my ...
0
votes
0answers
12 views

What are the differences between benign tumor and injury tumor? [on hold]

What are the differences between belign tumor and injury tumor? and Why injury tumor (for example when you get hurt and it swells) can not turn to malignant, and belign tumor can turn to malignant ...
2
votes
1answer
208 views

What are hot spots on human body?

Recently I have just discovered that a certain amount of the mobile phone frequency can be absorbed by human tissues. For example, this is the SAR info of iPhone 4s: Head: 1.180 W/kg 1 g Body: ...
6
votes
1answer
38 views

Can people with paralyzed eye muscles see?

As far as I am aware, the saccades of the eye are central to sight perception. If the eye is held still, the human stops seeing, even if light is reaching the retina and the visual pathway is intact. ...
1
vote
1answer
51 views

Role of Calcium and Magnesium in capacitation/acrosome reaction

During the acrosome reaction, the activation enzyme present in the sperm dissolves the corona radiata and zona pellucida enabling the sperm to reach the plasma membrane of the egg. Also calcium and ...
4
votes
2answers
33 views

What’s the reason for isovolumic contraction and isovolumic relaxation?

During cardiac cycle, there are two periods in which the heart volume doesn’t change, but there is a change in tension/pressure. It takes about 0.25-0.35 second to achieve this change. I searched in ...
1
vote
1answer
40 views

What specific sensory nerves act as receptors for “pins and needles” (neuropathy)?

According to this excellent answer, the difference between "pain" and "pins and needles" (neuropathy) is that different receptors (sensory nerves) trigger in reaction to different stimuli. Different ...
1
vote
1answer
35 views

How and where do nerves share pathways to the brain?

I am interested in understanding how pain receptors send signals to the somatosensory cortex (the part of the brain that registers various nerve signals such as pain, presure, temperatures, etc). ...
2
votes
0answers
35 views

How is atrial muscle stimulated, when the Atrioventricular (AV) Node is heart main pacemaker? [closed]

When the sinoatrial (SA) node is blocked, the atrioventricular (AV) node is heart pacemaker and controls ventricular contraction. The heart then beats 40-60 times per minute. What happens to atrial ...
-1
votes
0answers
29 views

What is the most recent cytokine discovered in human? [on hold]

Has anybody found an updated list of all cytokines in humans. I will appreciate that. To the best of my knowledge it is IL-32, is there a more recent one?
2
votes
1answer
26 views

Is it possible to estimate how much variation in common phenotypes is predicted by genetics?

Phenotypes such as; skin color, eye color, nose shape, lip size, limb proportions, and skull shape. Im trying to find a source for this quote. "If you ask what percentage of your genes is reflected ...
0
votes
0answers
23 views

What opens the lower esophageal sphincter(LES)? [on hold]

Is it true that the lower esophageal sphincter does not open under voluntary control? When a person swallows food, does something act to open it? If so, how is this opening mechanism called, and how ...
5
votes
1answer
187 views

Evolutionary reasons why you cannot tickle yourself but masturbate

There are obviously good reasons that explain why you cannot tickle yourself (see e.g. here). This got me thinking why it is possible to masturbate... Wouldn't it make more sense to not being able to ...
-3
votes
0answers
17 views

Do bigger things smell more or build more odor? [on hold]

My mother is always saying that, "The bigger the animal, the more the smell." I was wondering, at least to what degree (if it's actually true), how well this would apply. For example, my girlfriend ...
5
votes
2answers
120 views

Why do skin and nail go blue in cyanosis?

I have learned that Cyanosis presents with blue skin and nails. What is the reason for the blue coloration of the skin and nails? Why wont the skin and nails turn another color in the visible spectrum ...
-3
votes
1answer
40 views

Could we engineer humans to behave like insects? [closed]

First off, though complex, I'm assuming insects are at an earlier evolutionary stage than humans. That being said, could humans be genetically engineered to behave like insects? I'm not talking about ...
1
vote
1answer
48 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
votes
1answer
23 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 ...
3
votes
2answers
116 views

Why do human ears have a lower boundary for the lowest energy perceivable signal than eyes?

I am currently hearing a lecture about human machine interaction. The lecturer is not a biologist (neither am I, we are both computer scientists), but he makes some statements about biology which I ...
1
vote
1answer
29 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 ...
0
votes
1answer
38 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
votes
1answer
3k 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, ...
0
votes
0answers
21 views

Are certain genetic conditions/disorders predicate of weak genetics? [closed]

I have social anxiety, borderline personality disorder, phobias, mild obsessive compulsions, and other vague emotional problems therein associated with previously noted problems. My theory: I am ...
1
vote
1answer
18 views

What is the biological basis for tiredness after eating?

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 ...
1
vote
1answer
171 views

Perception of distant lights without glasses

I am fairly short-sighted and wear glasses pretty much all the time. Naively, I would expect that when I take my glasses off, the image I see should look very much the same as as a photograph that's ...
6
votes
1answer
84 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 ...
1
vote
2answers
91 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 ...
5
votes
1answer
949 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 ...
2
votes
1answer
28 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 ...
0
votes
0answers
18 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 ...
1
vote
0answers
14 views

Why am I feeling more hungry when lying on my back? [closed]

I noticed that when I lie on my back I feel more hungry than in all other positions. How is it possible?
0
votes
1answer
33 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?
2
votes
2answers
49 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
votes
1answer
49 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
votes
2answers
98 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 ...
1
vote
0answers
20 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 ...
7
votes
2answers
75 views

How can we measure cardiac output?

I could find a way which could find it by body oxygen consumption and there is another way to measure it by injecting drugs — measuring cardiac output by the so-called “indicator dilution method,” a ...
5
votes
2answers
79 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 ...
5
votes
1answer
36 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
votes
1answer
97 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? ...
10
votes
3answers
3k 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.
25
votes
1answer
14k views

How does laughing gas (N₂O) work?

Laughing gas (N2O), well, makes people laugh. How does just a gas make us do that, there has to be some hormones at work... So, I wanted to know how this works? What is the mechanism?
11
votes
1answer
165 views

Why doesn't HDL cause diseases like LDL?

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
votes
1answer
45 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 ...
3
votes
1answer
79 views

Why do men have a higher hematocrit (red blood cell count) than women?

The hematocrit, also known as packed cell volume (PCV) or erythrocyte volume fraction (EVF), is the volume percentage (%) of red blood cells in blood. It is normally 45% for men and 40% for women. ...
11
votes
2answers
139 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 ...