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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6 views

Why light fighters have better cardio than heavyweights?

In boxing, lighter fighters, like featherweights and lightweights, seems to have a better 'cardio' (they get tired well slowler) than, for example, heavyweights. Why this happens?
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0answers
30 views

Why sex is not allowed for children? [on hold]

Why sex is not allowed with children? As age increases, there will be decrease in sex hormones in males.
2
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1answer
14 views

Why are sperm cells not attacked by the female immune system? [duplicate]

Whenever a foreign particle enters into someone's body, it is attacked by the white blood cells. I just want how it is that, when sperms enter the female body, they are not attacked by the the woman's ...
5
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2answers
2k views

Why don't breast enlargements leave any marks of surgery on breasts?

If we get stitches, we get marks left on the skin, but there are no marks for breast enlargements. I saw a YouTube video about a breast enlargement wherein a doctor makes a cut. Where does the cut ...
3
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1answer
25 views

SNPs and locations

I am new to reading raw DNA. When comparing two people's raw data, why does one person have a different SNP than the other, at the same location, on specific chromosome? But on a different chromosome ...
4
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2answers
89 views

How does menstruation proceed during one period?

I'm simplifying things here: A. Does a woman bleed constantly, like a drop every 10 minutes? Two hours without pad or tampon and your underwear is dirty? or B. Does a woman bleed suddenly a ...
7
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3answers
100 views

Which fruit compounds affect the speed of fructose absorption?

Blood fructose levels are not regulated by insulin in the human body. This means that the body absorbs pure fructose very fast, and it raises the blood fructose levels rapidly. Do fruits/ vegetation ...
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0answers
24 views

Why do humans not regrow arms and legs? [on hold]

We regrow some things but not arms, legs, fingers, toes, ears, etc. Why not? Ignore this: I am being warned my question does not meet quality standards so I am adding this paragraph.
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0answers
16 views

Why does my silver hair now have gray roots [on hold]

My hair started turning gray/silver at an early age. After years of coloring it, I finally stopped coloring it ten years ago. I developed a beautiful head of silver/white hair. Slowly, my roots ...
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2answers
41 views

What are the differences between a benign tumor and swelling?

What are the differences between a benign tumor and an injury related swelling? And can swellings due to injury turn into a benign tumor?
2
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0answers
43 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
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0answers
31 views

Length of sleep time

Why do we wake up after 6-8 hours of sleep ? Why don't we sleep for lets say 20-30 hours ? What mechanism is it that controls when to wake us up and how does it determine the moment that we should ...
4
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1answer
57 views

What kinds of cells does human saliva contain?

I have heard that our saliva contains cells. What cell types can be found in human saliva?
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0answers
10 views

Swellings with Variegated consistency

I am interested in knowing the names of all swellings with variegated consistency. I have come across the following: Malignant swelling with partial necrosis Caseated tuberculous lymph nodes ...
1
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1answer
23 views

Dehydration from caffeine, alcohol and other

Tea, Coffee, Beer, Coke etc… I wonder if the benefit from amount of fluid we get from them is bigger or smaller then the handicap of dehydration. In other words it is worth to drink them if we want ...
2
votes
1answer
41 views

Dehydration by a tea, coffee, beer etc

For the long time I am trying to find out if the following is truth: They say that some beverages dehydrates. I heard that about tea (sometimes green, sometimes black, sometimes both), coffee, beer ...
2
votes
1answer
219 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: ...
3
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1answer
62 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 ...
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0answers
40 views

What is it a swell in the body? [closed]

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
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1answer
49 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
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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 ...
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0answers
27 views

Why Muscle Popups? [closed]

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 ...
7
votes
1answer
46 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
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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 ...
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1answer
42 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
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1answer
37 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). ...
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0answers
29 views

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

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
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1answer
28 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 ...
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0answers
23 views

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

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
194 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 ...
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0answers
18 views

Do bigger things smell more or build more odor? [closed]

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
124 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 ...
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1answer
43 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
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1answer
50 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
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
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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
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1answer
30 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
39 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
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, ...
1
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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
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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
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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 ...
1
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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
977 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
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1answer
30 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
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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
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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
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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
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2answers
55 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 ...