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
votes
1answer
546 views

What forms the human amniotic sac?

I am trying to understand the formation of embryonic disc for human and chick so the following question is related to here about formation of embryonic disc. I had thought that the amniotic sac forms ...
4
votes
1answer
289 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 ...
7
votes
1answer
396 views

Which human body hormonal systems exhibit 24 hour diurnal cyclical activity?

I'm researching the possible connection between the dream content and the activity of various organ or hormonal systems within the human body. I'm looking for information on biological cycles within ...
4
votes
1answer
140 views

What are the constraints when growing an artificial brain?

Are there any experiments on growing artificial brains from brain tissue? What are the constraints? Will such tissue grown to the mass greater than that of human brain surpass it in intellect or it ...
5
votes
1answer
764 views

Do eye muscles relax when you close your eyes?

I wonder whether the eyes muscle relax when you close them. Common knowledge told us the eyes muscle get tense when you stare at nearby object. If you close your eyes, you eye lids have 0 distance ...
7
votes
1answer
501 views

Why do people look different after a long sleep?

What happens during a long sleep that makes people look odd when they have just woken up? Why doesn't the same phenomenon occur in the case of a person who lies down for an extended period of time, ...
6
votes
1answer
5k views

Does consuming sodium benzoate (preservative E211) cause problems during pregnancy?

There seems to be strong evidence to support the claim that sodium benzoate (E211) causes hyperactivity in young children, e.g. Bateman et al. (2004) and McCann et al. (2007). This leads me to ...
12
votes
1answer
4k views

Why does scar tissue change color?

I was wondering why, when you are cold, scar tissue turns bluish or purple while original skin stays the same color. The only thing I can think of, is that maybe scar tissue gets less circulation ...
7
votes
1answer
215 views

Does cooking ginger reduce its anti-nausea effect?

There seems to be strong evidence to support the hypothesis that eating ginger helps reduce nausea e.g. during pregnancy (e.g. Vutyavanich et al.). It seems that gingerol is the active ingredient in ...
5
votes
2answers
485 views

How are the gene sequences of individual sperm and egg cells “randomized”?

What I mean by "randomized" is, in the place where an egg cell or sperm cell is made, what is the mechanism by which each one is not made identically? Though I am a layman, I'm pretty sure that if the ...
13
votes
1answer
378 views

Is it correct that the body only responds to the most painful stimulus?

I'm rather ashamed to say that this question is partly based on an episode of House. I have previously heard that, if there are multiple simultaneous painful stimuli, the mind will only feel the ...
2
votes
1answer
82 views

Is the protein in teardrops still attached to cells, or is it released and free-flowing?

A ScienceDaily article says that the protein in teardrops can kill bacteria. But how does it reach the bacteria?
17
votes
2answers
3k views

What is the mechanism behind “acquired” alcohol tolerance?

I can understand natural variation in alcohol dehydrogenase (ADH) in a population leading to variation in rate of inebriation (after controlling for other variables -- e.g., mass, food consumption, ...
10
votes
1answer
123 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 ...
12
votes
2answers
177 views

Why is the microbial ecosystem of the gut so susceptible to disruption by pathogens?

From all accounts, it seems as if the Escherichia, Enterobacter, etc. that live and thrive in the human gut are pretty well entrenched. I know that these microbial populations are often analyzed as ...
12
votes
2answers
2k views

How does a brain distinguish stimuli?

If all the brain ever "sees" is action potentials, how do we know that one set of action potentials denotes a flash of light, another one signifies a loud sound, etc ?
8
votes
1answer
2k views

Effects of Polyphasic vs Monophasic sleep in humans

Why do humans practice monophasic sleep cycles? When altering one's circadian rhythm to a Polyphasic sleep schedule, how much would that affect development? Is Monophasic sleep (once per day) ...
9
votes
1answer
109 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 ...
7
votes
1answer
161 views

Can oxygen diffuse out through the lungs?

Let's say you accidentally walk into a room pressurized with pure nitrogen (or you're jettisoned into space). Within a couple of seconds, the partial pressure of oxygen within your lungs drops to 0. ...
7
votes
2answers
498 views

Where does vasoconstriction occur in limbs?

When cold or in shock a person's blood vessels constrict in order to preserve heat or to move blood flow to protect vital organs. I am interested in the mechanism by which this is achieved. Does ...
10
votes
2answers
1k views

Do human beings have pheromone receptors?

What is the current consensus on whether or not humans have receptors that detect pheromones? If there are purported receptors, in what anatomical areas are they located? With what organ systems do ...