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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10
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3answers
327 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 ...
10
votes
2answers
237 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 ...
10
votes
2answers
369 views

Could an “overactive” brain increase the chances of Alzheimer's Disease?

From Raichle ME. 2010. Two views of brain function. Trends in cognitive sciences 14: 180–90: Alzheimer’s disease (AD) is the most common cause of progressive cognitive decline and dementia in ...
9
votes
2answers
25k views

Which shades/hues of color are easiest to distinguish for humans?

I'm trying to represent data graphically and am using a variation of hue/lightness to distinguish one data point from the next. I would like to use a color that would allow me to convey most ...
9
votes
1answer
104 views

Why is there an extended delay before G.M. liver cells are attacked by the immune system?

In this BBC article a trial is described where patients with B-Haemophillia are infected with modified Adeno-associated Virus 8 which contained the genes for Factor IX clotting protein. Trials seemed ...
8
votes
1answer
556 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 ...
8
votes
2answers
628 views

How much weight/volume do microbes occupy within the human body?

Microorganisms constitute the bulk of all the biomass on Earth. I weighed myself yesterday, and wondered how much less I would weigh if I were completely free of bacteria and microbes, inside and out. ...
6
votes
4answers
2k views

Why we have no enzyme to digest cellulose?

As we know, cellulose is the most abundant polysaccharide in nature. Why don't we have any enzyme to digest cellulose?
6
votes
1answer
2k views

What causes the colors we see in eyes?

Genetics aside, what are the biochemical reasons the different colours of human irises? Also, related, how does eye colour change, particularly in childhood? (example: my eyes used to be blue, ...
6
votes
1answer
157 views

How does skin healing work?

I stacked my bike and split my head right open. About three weeks later the scab falls off and the skin is sealed over, like magic! How does it all work? How does the brain know that part of the ...
4
votes
1answer
97 views

What light intensity determines the start/end of a photoperiod in humans?

I'm reading this article, which discusses the influence of Long Photoperiod (LP) and Short Photoperiod (SP) on melatonin production: HIOMT drives the photoperiodic changes in the amplitude of the ...
4
votes
1answer
528 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
73 views

How many different smells can a human recognize?

How many different smells can a human recognize? If the space of smells is not discrete, how many dimensions it has (for example, the space of colors is three-dimensional).
1
vote
2answers
111 views

Which was the last significant event in human evolution? What's next?

At 10.000 BC (12 ka), we became the last of the Homo species on Earth. In evolutionary terms this is a very little time range to something happen, but I'm wondering anyway, in this meantime which are ...
1
vote
1answer
1k views

What would be the best design for spike-and-recovery and linearity-of-dilution validation experiments in one 96-well ELISA plate?

I have searched in the web for a detailed explanation of doing such validation experiment, but unfortunately couldn't find a satisfactory one. I came across the following sources: Thermo ...
19
votes
2answers
6k views

What causes fingerprints to form and why is the pattern formed unique?

I've found research that suggests that the reason we develop fingerprints is because they aid us with feeling surfaces (Scheibert, et al. 2008) and not to increase friction and help with the gripping ...
14
votes
2answers
148 views

Relationship between our microbiome and personalized nutrition

Recently, it has been asked whether there are 'metabolic types' between humans that can benefit from a sort of personalized nutrition. One answer suggested that one discerning factor could be the ...
13
votes
3answers
3k views

What causes the development of antibiotic-resistant strains of bacteria?

I understand bacteria have become resistant to antibiotics due to selection pressures, but how do resistant bacteria process antibiotics when exposed to it, compared to non-resistant bacteria. Also, ...
11
votes
4answers
3k views

What nutrients can humans absorb in the mouth?

For instance, I realise being able to absorb simple sugars in the mouth is pivotal in the rapid action of oral glucose gel. Thus I was wondering what nutrients in general can be absorbed directly ...
11
votes
1answer
723 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? ...
10
votes
1answer
121 views

What portions of the brain have drastic changes in activation when we “sense” someone is there?

I was watching an old Arnold Schwarzenegger movie ("Commando") where he plays an elite soldier (surprise). An enemy tries to sneak up on him, and Arnold says that he smelled the other guy ...
9
votes
1answer
299 views

Can Naegleria fowleri enter through wounds into the bloodstream?

All the sources I've read said that Naegleria fowleri enters the brain through the nose. But lets say that someone had cuts on their arm or leg and they are swimming in water that is conducive to ...
8
votes
1answer
8k views

What is the composition of human feces?

Are there any studies or general information on the composition of human feces? I'd specifically like to know the percentage of carbohydrates and amino acids relative to the amount that was ingested ...
8
votes
1answer
3k views

How does sodium in one's diet affect blood pressure?

Due to high blood pressure, my doctor has recommended I go on a low-sodium diet. So, that got me wondering what it is about sodium that drives this recommendation? What does sodium do to a body ...
6
votes
2answers
141 views

How would the human body adjust to sleep times if we were to live in a place with different day lengths?

You sleep at night and are active during the day that's how things work for humans, but theoretically if a human whose parents lived on earth were to be born in another planet resembling earth but the ...
6
votes
2answers
7k views

Can positive and negative blood type of a couple lead to miscarriage?

I want to know can $+ve$ and $-ve$ blood group of a couple could be a cause of miscarriage in pregnancy?
6
votes
1answer
197 views

Is there a normal human melatonin concentration to light level curve?

I'm looking for a graph or a curve that would show the typical concentration of melatonin in blood or saliva for humans over 24 hours. It would be good to know the photoperiod for the same human as ...
6
votes
2answers
226 views

Is there such thing as a generic “metabolic type”?

A while ago I picked up a book called "Eat right for your metabolic type". The book discussed the effects of the endocrine system on the overall shape and the speed of metabolism. The book outlined ...
6
votes
2answers
251 views

What is the eye muscle status when you stare at distant view through a glass wall?

The book said when you look at object close to you, the eye muscles contract and vice versa. I wonder what will be the status of the eye muscles when I stare at distance view (such as a mountain) ...
5
votes
3answers
2k views

Why does it hurt when you take sweets, if you have cavities in your teeth?

When you have cavities in your teeth taking any sweetend drinks or food causes sensitivity or pain. What could be the reason?
5
votes
2answers
509 views

The probability of indirect human fertilization?

What is the probability of conception in situations when sperm isn't directly ejaculated into the woman's vagina, like: The man's or the woman's hands come into contact with sperm, for example when ...
5
votes
1answer
732 views

The genetic and physiological origins of laughter?

This Wikipedia article defines laughter in many terms, such as... "a visual expression of happiness, or an inward feeling of joy" and "a part of human behavior regulated by the brain, ...
4
votes
1answer
101 views

Getting goosebumps at will

I can get goosebumps at will, regardless of the environment. Its mostly visible on my arms, and I can feel it on my head. It requires some level of concentration to achieve this. My questions are : ...
4
votes
1answer
4k views

Does mixing alcoholic drinks really make you more drunk?

There is plenty of anecdotal evidence ("beer after wine and you'll feel fine, wine after beer will make you feel queer") that mixing alcoholic drink types leads to a stronger effect, but I can't find ...
4
votes
2answers
119 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 ...
4
votes
1answer
284 views

Human sleep cycles and dream times, what influences the timing and intensity? Sleep history included

I'm doing sleep and dreams research and have developed an iPhone application to help me track my bedtime, rise time, sleep onset and also mark dreams. The app also monitors overall activity overnight ...
3
votes
3answers
93 views

Why can't you just take a vitamin? Why you need a healthy diet on top of that?

From what I understand, your body needs certain amounts of vitamins and minerals to maintain health. Why can't we just take enough pills to obtain these vitamins and minerals?
3
votes
1answer
244 views

How are melatonin levels measured in humans?

I'm wondering how it is possible to measure diurnal variations of melatonin levels in humans. I keep reading that there should be a large difference in amplitude between melatonin levels measured at ...
3
votes
0answers
107 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 ...
3
votes
1answer
413 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 ...
2
votes
1answer
50 views

How usable is the Human Metabolic Model to predict biomass?

In order to use the Human Metabolic Model for Flux Balance Analysis of specific cancer cell lines, we would like to know what sort of flux values have been determined for the Human Metabolic Model. ...
2
votes
3answers
447 views

Is there such thing as “half-life” of dopamine?

If a dopamine is released at T=0 and binds to receptor D2, what determines the time when the concentration of this neurotransmitter bound to the receptor reaches half of the original concentration? In ...
1
vote
1answer
27 views

Regarding the relation of observed human nature with evolution and/or genetics [closed]

Can the behavior/psychology of a human be genetic or is it an acquired trait?
1
vote
1answer
29 views

What are good data on the Human Metabolic Model and where can I get them?

Trying to get a good SBML representation of the Human Metabolic Model for use in Flux Balance Analysis and drug targetting (i.e. gene knockout) simulations. What are good sources for these data? ...
1
vote
1answer
113 views

Determining a patients biological age?

I am looking for an algorithm that shows the exact coefficients some variables that have on a hospital patient's chronological age versus their biological age. I understand a lot of the variables ...
1
vote
1answer
70 views

Body's decomposition

Does a human body decompose in a completely sterile environment ? If yes, what decomposes it ? And how fast ? What happens in vacuum ? Can it remain exactly the same ? Thanks
1
vote
1answer
97 views

Agony, Hydrophobia and viruses in the light of evolutionary principles

I'm undergraduate physics student, but I've always been interested in biology. So I have a couple of questions about an application of the evolutionary principles to practice. Agony as the last ...