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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7
votes
2answers
151 views

How was the guided daily amount (GDA) calculated?

We are constantly shown nutritional information on food packaging stating this food contains "x" amount of your guided daily amount. A linked to the values is here. How were these values calculated? ...
11
votes
3answers
1k views

What happens to dextrorotatory amino acids in humans?

As indicated by this question, most of the amino acids in the human body have the L-chirality. As enzymes also have handedness, what happens to the D-amino acids that end up within the human body? Are ...
9
votes
2answers
329 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 ...
4
votes
1answer
1k 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 ...
1
vote
1answer
57 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 ...
7
votes
3answers
242 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
84 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 ...
19
votes
2answers
660 views

Why is rabies incurable?

I'm still not sure about the mechanics that lead to rabies being incurable. I know that it can be treated before any symptoms show up, but why is it that once symptoms show the person is a dead man ...
6
votes
1answer
135 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
450 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 ...
4
votes
1answer
76 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 ...
2
votes
1answer
311 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 ...
8
votes
1answer
523 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 ...
4
votes
1answer
660 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 ...
7
votes
1answer
375 views

How fast do different organs turn over cells?

It is said that the human body turns over all cells or molecules in 7 year cycles. This is not quite correct, because there are different organs changing at different speeds. My interest is what is ...
6
votes
1answer
622 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
votes
1answer
101 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?
6
votes
1answer
59 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 ...
10
votes
2answers
255 views

What can the timing of human urination tell about the human's physical condition and circadian rhythms?

I've noticed a peculiar phenomenon. A subject drinks 400 ml of water, then observes time until the urge to urinate is felt. The time is 15 minutes. The subject releases water. 14 minutes later another ...
3
votes
0answers
117 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 ...
4
votes
1answer
105 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?
1
vote
1answer
389 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?
2
votes
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 ...
11
votes
1answer
777 views

Is there an evolutionary advantage to crying when sad?

It seems as though the act of crying when sad does nothing to relieve that sadness. Is there an advantage to crying from an evolutionary perspective, or is it the end result of a different process? ...
3
votes
1answer
87 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? ...
4
votes
1answer
79 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 ...
26
votes
3answers
419 views

Is telomere length a reliable measure of health/lifespan?

Several companies are commercializing tests for telomere length such as this one here. I understand the basic mechanism for why telomeres shorten during DNA replication, but how good is the evidence ...
11
votes
3answers
209 views

Does current evidence support the use of resveratrol as an anti-ageing drug?

A while back there was a lot of noise about resveratrol, a naturally occurring phenol which was touted as a potential anti-aging drug due to its role in regulating the SIRT 1 gene. A number of studies ...
5
votes
1answer
732 views

Is there a relationship between efficiency of cellular metabolism and warm-blooded-ness?

My BIO 101 book states that when human cells convert glucose to ATP, the process is only approx 35% efficient, and much of the potential energy is lost as heat. However, that heat is useful to us in ...
3
votes
1answer
432 views

Could inhibition of progerin formation slow the rate at which a body ages?

According to wikipedia, progerin is activated in senescent cells. The protein itself is known to be the cause of a rare affliction 'progeria' - a disease marked by accelerated aging of the body. This ...
1
vote
2answers
558 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
votes
0answers
35 views

Can progerin formation be triggered explicitly? [closed]

Corollary to my question - Could inhibition of progerin formation slow the rate at which a body ages? Is it possible to activate/trigger progerin formation explicitly? Say, by some hormonal/chemical ...
0
votes
1answer
483 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?
5
votes
1answer
1k views

Do hot drinks cool you down?

It is quite the old wives tale that drinking a hot drink cools you down. If you don't really think about it it does seem somewhat logical: increasing temperature will cause your body to try and cool ...
5
votes
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 ...
3
votes
0answers
248 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 ...
5
votes
3answers
524 views

When to measure resting heart rate and blood pressure for following day-to-day trend?

I'd like monitor my resting heart rate and blood pressure to see how they are affected by regular cardiovascular training and other events in life. When should I take the measurements in order to ...
13
votes
2answers
629 views

Does testosterone increase female sexual behavior?

According to my lecture notes testosterone generally increases sexual behavior. Given that it's generally thought to be the male hormone I'm not quite sure whether they mean that it also increases ...
8
votes
2answers
200 views

Is there a consensus on whether or not race exists on a biological level?

The most recent survey I could find was from 1985 which said that 16% of biologist disagreed that "[t]here are biological races in the species Homo sapiens." I was wondering if there's been a change ...
7
votes
2answers
5k views

What are the consequences of voluntary total celibacy?

Psychologically this might be a tough question, but in means of biology, what are the effects of total celibacy on the gonads and the nervous system concerning both man and woman in short and long ...
6
votes
1answer
384 views

Is it purely the nervous system causing vaginal lubrication (arousal)?

My girlfriend was watching some documentary on TLC about a paralyzed woman getting pregnant. I believe that woman still has some feeling, as she spoke about feeling the effects of a bladder ...
-3
votes
1answer
719 views

How does protein help to cure wound? [closed]

I understand that the protein helps to repair body tissues. If I increase the intake of protein, would it help to cure the wound more quickly? I would like to know how does the protein reaches the ...
1
vote
0answers
57 views

Are the intestinal flora substantially different within a diverticulum of the colon?

From the Wikipedia page for the vermiform appendix: This proposal is based on a new understanding of how the immune system supports the growth of beneficial intestinal bacteria, in combination ...
0
votes
1answer
269 views

Why does a drop of water penetrate deep sleep? [closed]

Sleeping under the stars, a breeze carrying a few drops of water came by. The sense of water drops on my arms woke me up. I'm curious Why does the sense of a drop of water on one's body penetrate ...
6
votes
1answer
117 views

Latency to audition in human beings?

On average, in a human being with no neurological deficits, how long does it take for a sound which is sensed in the ear to reach the cortex? Which brainstem structures are most responsible for the ...
4
votes
1answer
137 views

What biological systems are affected by Vitamin B6 (or B vitamins in general)?

B vitamins and particularly the B6 vitamin appears to the one of the main ingredients in energy drinks. There has been anecdotal evidence from people interested in dreaming that ingestion of vitamin ...
8
votes
1answer
574 views

What causes knuckle “popping” and the feeling of relief that comes from it?

Many people like cracking their knuckles. I have always been curious about it. What happens when we crack knuckles? What creates the POP sound? Why do we get a relief-like feeling after doing it?
5
votes
2answers
244 views

Energy use by muscles, actual work done by muscles and more

Lately, I've started exercising in the gym and outside. I've also started to look at the details of food I eat. Food usually has a label saying the amount of energy is inside it. For example, some ...
4
votes
1answer
285 views

Can humans shorten their sleeping patterns?

Can sleeping patterns be trained, or are they genetic? I read that a human needs to sleep at least 4 hours. Can sleeping time be reduced without having a negative impact?
2
votes
2answers
187 views

How might I break down bread into glucose in a model of the human digestive system?

I need to make a model of the digestive system. It would be really nice to actually show it in action, such as by breaking down bread into glucose or something similar. Is this feasible with a small ...