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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2answers
126 views

Ultrasound during pregnancy

In a hospital I can see a long queue of pregnant women waiting for their turn for ultrasound. Is it safe to go through the ultrasound during pregnancy, especially during last few weeks? Is ...
9
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1answer
2k views

What determines testosterone exposure in womb, baby's genetics or mom's body?

I read this article which has the following quote: The ratio between index and ring finger is believed to be linked to exposure to the male hormone testosterone in the womb. And I wonder what ...
12
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2answers
235 views

Why do most breast cancers occur in women?

According to Korde et al. (2010): Male breast cancer accounts for less than 1% of all cancers in men and less than 1% of breast cancers. This raises the question: Why do most breast cancers ...
3
votes
1answer
246 views

What is the relationship between Homocysteine and Norepinephrine metabolic cycles?

I've been researching neuromodulators and have taken a look at the Norepinephrine/Noradrenaline system. The diagram of biosynthesis of Norepinephrine is presented in the wikipedia article: ...
8
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3answers
478 views

Does human digestive system benefit from eating same kind of food consistently?

Here's the reason why I'm asking: I've heard that it takes some time for pets(cats/dogs) to adjust to a different dry feed, where the new feed has to be mixed with the old one, slowly replacing the ...
2
votes
1answer
7k views

Ramifications and possibility of a diet consuming exclusively of human semen

Semen is a thick, nutritious liquid, rich in vitamins (such as C, B12), amino acids, lipids, monosaccharides (fructose), et cetera. Can semen's ability to fulfill the needs of human organism provide ...
0
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1answer
251 views

From which ancestor species did humans inherit orgasm?

From what ancestors did humans inherit orgasm? Do fish experience orgasm? Are the male and female orgasm the homologues that can be traced to the time when there was no difference in sex between ...
4
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1answer
2k views

What does vitamin B6 and B12 absorption depend upon?

I'm looking at my question about homocysteine metabolism and am doing a followup inquiry into vitamins B6(Pyroxidine) and B12(Cyanocobalamin). I've found this interesting bit about vitamin B12 and am ...
9
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2answers
487 views

Do twins “run in the family”?

My wife and I recently found out that we are going to have twins and so nearly everyone asks if we have a family history of twins. Now I know that the answer for me is that it doesn't matter—as ...
6
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1answer
951 views

Are there any effects of elevated Cysteine levels on cognitive function?

I'm looking at this diagram of homocysteine metabolism and see two distinct pathways that the amino acid may get metabolized to: with vitamin B12 it gets converted back into methionine, while with B6 ...
2
votes
1answer
67 views

What is the role of Homocysteine in cognitive function?

I'm looking at this link : Homocysteine and cognitive impairments and am looking for more information on specific cognitive impairments associated with elevated levels Homocysteine. That article is ...
14
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2answers
35k views

How many human cells are there in our body, on average?

How many human cells are there in our body, on average? Wikipedia says 1013: Bacterial cells are much smaller than human cells, and there are at least ten times as many bacteria as human cells in ...
3
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2answers
154 views

Is it possible to correctly identify presence of Y chromosome with external physical test only?

I asked a question related to the third sex, and I came to know that its always possible to categorize a human to male or female with presence of Y chromosome. Now, I have another question. Is there ...
16
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6answers
2k views

Human evolution: Where *exactly* did the first human come from, whose parents were not?

Layman here. So I have never really quite understood this facet of human evolution, (or any other for that matter), in that, I understand the evolutionary process, but I get lost on the 'border' ...
4
votes
1answer
118 views

Is there an advantage to having cellulite

There are many ads nowadays advertising cellulite removal, and it causes me to wonder if there is an advantage to having cellulite or if it is just a result of too much fat unevenly spread? Is it ...
4
votes
2answers
497 views

Does making yogurt from non-pasteurized milk work against possible disease bacteria?

In the past, when there was no pasteurization, could making yogurt from milk lower the chance of getting infected by bovine tuberculosis (or other diseases from infected milk)? For example, would ...
7
votes
3answers
270 views

What alternatives are there to the amyloid hypothesis?

Given the recent failure of the Bapi clinical trial, there is a lot of questions that have arised from he amyloid hypothesis. However, I can't really think of many other mechanisms that don't involved ...
4
votes
1answer
615 views

Why do rod cells not recover after bleaching upon exposure to bright light?

I'm confused as to why, when exposed to bright light, rod cells cease to function. I understand that exposure to bright light bleaches all of the rhodopsin, but...so what? Why doesn't the bleached ...
6
votes
1answer
776 views

What is Mendelian Randomization, and how is it used to infer causality in epidemiology?

Studies of human traits and diseases are inherently confined to observational studies, known as epidemiological studies. This can make it very hard to determine what actually causes a particular ...
10
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3answers
417 views

Athletes: nature vs. nurture?

Having watched a lot of olympians the last few weeks, I was struck by how many of them have actually spent their wholes lives/careers training for their one event (be in running a marathon, or ...
4
votes
1answer
89 views

During human ageing, which immune cell sub-types are most affected?

It is now well established that human ageing is accompanied by an increase in systemic, low-grade (chronic) inflammation, sometimes termed inflammaging (Franceschi, 2007). This is in part due to more ...
6
votes
1answer
158 views

Why are pilots under the illusion of gaining altitude without doing so?

We had a lecture about the balancing systems of the body (mainly the otolith organ / semilunar canals) in which a case was described where a pilot crashed into a ship. He was supposed to keep his ...
4
votes
1answer
858 views

When is the lactase in lactose-free milk active?

Recently we have started suspecting that one of our children has hypolactasia (lactose intolerance), and so accordingly I have had my first exposure to lactose-free dairy- and dairy-like products. In ...
3
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1answer
375 views

How does the brain instinctively know the math behind Newtonian Physics?

A 10 year old child does not have the intellectual power to accurately calculate the energy required to throw a ball an arbitrary distance. Yet they are able to accurately throw a ball at a ...
6
votes
1answer
801 views

Is there a biological basis to physical attraction?

Is there something encoded within us that makes us attracted to, e.g., someone taller or shorter with blonde or brunette hair with green or blue eyes? Or, is this phenomenon completely based on ...
6
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1answer
105 views

What is the biological mechanism linking temperature and probability to be infected with a virus?

It is common knowledge that when you're cold you could get a cold. What is the mechanism linking temperature and viral infection?
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2answers
1k views

Is there any biological reason that professional swimming is dominated by white people?

I suppose that the question should be turned around to "Why is it extremely rare to see black people competing in professional swimming?" because it is the absence of this phenotype while watching the ...
3
votes
2answers
151 views

What is the biological basis for a human's ability to think clearly and be aware while “fighting/competing”?

I'm interested in learning more about the biological systems or hormones or parts of the brain that affect short term (<15 minutes) ability to concentrate attention on the task and be aware of the ...
3
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0answers
132 views

What controls the feeling of discomfort/comfort before and after sleep?

I'm interested in which biological systems or hormones are involved in the following phenomenon: Before sleep it may be difficult to find a comfortable position, and muscular aches and pains are more ...
6
votes
1answer
61 views

On the effect of polluted air on health. Is it more gradual, or more immediate?

I've heard time and again that living in São Paulo (a large city in Brasil) takes 1.5 years from your life expectancy. The allegation is that this happens because of air pollution. I am just ...
4
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1answer
113 views

Is there a correlation between incidence of type 1 diabetes and vitiligo?

Does the data indicate that if you have one, the probability of you having the other is higher than that of someone who doesn't have the one?
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1answer
575 views

Is sperm contagious?

A person may have a cold or any other disease that is an airborne-infection. Is their sperm also contagious? Should the person take any precautions?
8
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1answer
740 views

A timeline of the odds for survival for fertilized eggs and fetuses

I'm looking for data to build a timeline of the odds for survival of a fertilized egg, i.e., What are the odds it'll last a week? What are the odds it'll last a month? 2 months? (and so on ...
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votes
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 ...
4
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1answer
105 views

Are there any situations in which phenylephrine is preferred to pseudoephedrine?

In the mid 2000s in the US, due to issues of drug enforcement, pseudoephedrine containing medications were brought behind the pharmacy counter and in most cases require ID, and phenylephrine was ...
10
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1answer
203 views

Does stress physically age our body?

Going by the assumption that stress eventually triggers a flight/fight response, and the subsequent realization that flight/fight puts the body in a system of readiness to use it's available resources ...
8
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1answer
338 views

How do the pharmacodynamics of the NSAIDs differ and are there “resistant” COX phenotypes?

I know that the non-steroidal anti-inflammatory drugs (e.g., aspirin, ibuprofen, naproxen) affect the enzymes cyclooxygenase (types I and II). Is there any difference in the degree to which these ...
3
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1answer
91 views

Predictable microchimerism

I read in New Scientist recently that microchimerism occurs between previously born siblings and grandparents, not just the mother. Do we know which parts of the genome are likely to be transferred? ...
2
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1answer
2k views

What is the “lifecycle” of an average eschar and what types of cells are involved in each stage?

(after some deliberation in the comments, I've decided to make the question more general) An eschar or "dry scab" often forms at a site of injury over a large cut or sore. It seems as though the ...
4
votes
1answer
88 views

What are possible health risks to women having large numbers of children?

What is the possible health issue the women would face in this record? The record for most children born to a single couple belongs to the first wife of Feodor Vassilyev of Russia. In 27 ...
14
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1answer
1k views

Are human bodies programmed to die?

Following from this question: What is the evolutionary advantage of death?: Is there any evidence that human bodies have systemic self-destruction built into their developmental program? I'm not ...
6
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2answers
483 views

What is the relationship between migraines and histamine?

A family member suffers from migraines so I have been reading a little around the subject. There seem to be any number of "triggers", but I have seen mention several times of the role of histamine ...
5
votes
1answer
738 views

Total amount of CO₂ / Oxygen in Bloodstream in Humans

How much carbon dioxide and oxygen from/for respiration are in the bloodstream at any one time? (mass per litre of blood or similar) And would there be much more aside from the blood in tissue, e.g. ...
5
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2answers
7k views

Why do we sweat after drinking water and running?

Why do we sweat after running? Also we sweat sometime after drinking lots of water. Why it is so? Can someone please enlighten me in this regard?
14
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1answer
2k views

Why does hair turn grey or white, and why does it happen later for some?

The question is pretty simple: what is happening molecularly when hair turns grey or white? I would imagine that it is due to the lack of a particular compound. I'm also interested in why some ...
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2answers
800 views

Shouldn't evolution have taken care of baldness already?

It is my understanding that the hair on the head is there to protect us from sunburn. I've never seen a bald animal, so isn't evolution in charge of addressing these type of things? How is it that ...
0
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1answer
612 views

Are there examples of the green beard effect in humans?

Green-beard effects are genes that: Produce an effect that can be detected Produce preference to others with the same effect Are there any examples of this in humans?
4
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2answers
170 views

What is the purpose of the adrenal medulla?

The adrenal medulla is less of a 'real' endocrine organ like the others in the endocrine system and much more an extension of the sympathetic nervous system. In fact, its chromaffin cells are modified ...
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1answer
2k views

What are tendons made of specifically

From what I read on wikipedia they are made of collagen. Collagen is just a protein. Right? How is this collagen structured (I imagine like fibers). Aren't there cells in this fibers as well? From ...
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0answers
307 views

What is the timing of information assimilation within a human brain? [closed]

A little background: I'm an avid dreamer and have great dream recall, sometimes up to 5-7 per night. In my experience, I can sometimes trace some elements of the dream to an event that occured ...