This tag is for questions about the general biological features of human beings (as opposed to the biology of non-humans).

learn more… | top users | synonyms

5
votes
4answers
8k 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
vote
1answer
32 views

Human Demography - Where can I find this statistic?

In "An Introduction to Genetics" by David J. Merrell, copyright 1975 by W.W. Norton + Co., p. 742, in the Chapter "Genetic Counseling and Eugenics," the author states: "... 50% of the women produce 85%...
-3
votes
0answers
23 views

How does Jyoti Amge defy aging? [on hold]

She's over 18 and yet she looks almost exactly like a small version of a normal little kid. How does she have such an undistorted slown down aging unlike Nicky Freeman described at https://au.news....
17
votes
2answers
537 views

Can parts of a human brain be asleep independently of each other, or vary in the times required for them to fall asleep?

I know that some birds and marine animals can continue complicated activity (swimming, flying?) while one hemisphere of their brain is asleep. I'm interested if human brain has some parts of it that ...
17
votes
3answers
4k views

What causes a 'stuffy' or 'runny' nose when you have a cold?

When humans get the common cold, a common symptom is a stuffy or runny nose. Is that the body's immune response or is that the virus's doing?
0
votes
0answers
12 views

Are apples really better for the immune system than most fruit? [migrated]

"An apple a day keeps the doctor away", the saying goes, implying that apples are somehow especially good for the immune system. But does this idiom have any validity to it? Are apples high in ...
0
votes
1answer
40 views

Amino Acid requirement + intake in relation to diet + meat type [on hold]

I was arguing with a friend: I said: The Yulin festivals cannot be condemned by western culture, as we also kill animals in equally cruel ways. She said: It isn't just that the killing is cruel, ...
0
votes
0answers
34 views

Stopping the Gag Reflex: How and why does it work?

I was talking to some friends over the weekend, and one of them made a comment about gagging. He said that he read or watched that clenching your thumb with your other fingers (making a tight fist ...
14
votes
1answer
153 views

What's the mechanism for being mentally tired?

I notice that after long tests, or long periods of critical thinking, my body and mind feel noticeably tired. Why does this happen? Are the neurons in my head not firing as quickly, or is there just a ...
0
votes
0answers
32 views

Why people have less hair than other primates? [duplicate]

Well as you can figure out, most primates such as monkeys, gorillas and chimpanzees, have all their body covered with fur. As we know they are evolutional "relatives" to us humans, but we dont have ...
3
votes
0answers
58 views

Why did we evolve to control our breath?

I had this question in my mind and tried to think of why we would evolve to be able to control our breath. I remembered the Aquatic Ape Hypothesis, which makes a lot of sense and would explain it, ...
1
vote
0answers
41 views

Why is sex pleasure giving activity but not childbirth?

Asking from an evolutionary viewpoint. Sex is a pleasure giving activity so that it encourages reproduction and spreading of genes. But childbirth ,the most crucial part of the reproductive process, ...
4
votes
1answer
90 views

Can the human body create glucose out of fat?

I read conflicting views about whether or not the human body can create glucose out of fat. Can it?
7
votes
4answers
13k views

Why do men have a higher hematocrit (red blood cell count) than women?

The hematocrit, also known as packed cell volume (PCV) or erythrocyte volume fraction (EVF), is the volume percentage (%) of red blood cells in blood. It is normally 45% for men and 40% for women. so,...
4
votes
1answer
51 views

Cancer biology: Can tumors form from cells that are genetically identical to non-cancerous cells?

Can a tumor begin to form without any genetic mutations? I'm specifically interested in a tumor which could later lead to cancer.
0
votes
2answers
51 views

How is UV light damaging DNA as the chromosomes are deep in the cell?

When UV light is on your skin it has to go through the cell membrane and to the membrane of the core. So it looks like that the DNA is protected. But it probably isn't. But can't membranes not been ...
0
votes
1answer
30 views

Does mechanotransduction of cells play a role in the biocompatibility of titanium?

What exactly is mechanotransduction as the information varies between sources. Some sources indicate that mechanotransduction is the underlying principle where cells pull on the surface they grow on ...
2
votes
0answers
73 views

Why does it take many sperm for one sperm to fertilize an egg?

Hundreds of acrosomes must undergo exocytosis to digest holes in the zona pellucida. This is one case that does not bear out the adage, “The early bird catches the worm.” A sperm that comes along ...
0
votes
1answer
59 views

Evolution to store limited Fat

Why are our bodies not evolved to store only limited amounts of fat, which won't kill us with all diseases associated with obesity? Wouldn't obese people die faster and clean the gene pool for people ...
4
votes
2answers
10k views

Applying saliva to mosquito bites

Is it true that; when you apply your own saliva to a mosquito bite it would stop itching ?
7
votes
1answer
4k views

Why do people sleep with their eyes open?

It's a fact that some people sleep with their eyes open, but why does that happen? Is it normal behavior, not a symptom of any sort of disorder? Are there any (dis)advantages to sleeping with eyes ...
1
vote
1answer
12 views

How do molecules signal pre synaptic neurons to activate? [closed]

How do molecules signal pre synaptic neurons to activate? and also is it more the structure or the elements in the molecule that allows it to activate the neuron also how do molecules bind to ...
4
votes
0answers
78 views

Do animals have different taste preferences within the same species?

Humans (especially children...) seem to dislike certain foods or drinks, that other humans seem to like. Common examples are coffee, french cheeses, olives, milk, fish and cabbage. Are there examples ...
9
votes
1answer
15k views

What is the standard deviation of adult human heights for males and females?

The wikipedia article on human height reports mean height for many different countries by sex but it does not report standard deviations. What is the standard deviation of adult human heights within ...
1
vote
2answers
112 views

How do I tell if the mosquitos in my New York City apartment can carry Zika?

The species that carries Zika, A. aegypti, is unlikely to be found in New York. However, the related species A. albopictus is prevalent and quite concerning. So this question is focusing on A. ...
3
votes
0answers
31 views

Why does crippling pain exist? [closed]

Some kinds of trauma can cause pain so severe that it makes you unable to move or do anything at all. It may put you out of action and unable to help yourself because of how excruciating it is. ...
0
votes
0answers
43 views

Is there an evolutionary advantage associated with migraine? [duplicate]

I have read Wikipedia article on Genetics of migraine headaches and I don't buy it Because genetics influence susceptibility to migraine, it can be shaped by evolution. Fitness-impairing ...
1
vote
2answers
65 views

Difference between water and tea [duplicate]

My friend heard that tea is worse for drinking than water because "cells have a special membrane and tea has special supplements and membrane doesn't let tea pass and this is why skin is dry even when ...
2
votes
1answer
83 views

Which part of the reflex arc takes the longest time?

If the reflex arc is composed of 4 parts: Activation of sensory receptors, Conduction to and from the CNS, Transmission across the neuromuscular junction & Activation of the muscular contractile ...
3
votes
2answers
70 views

What neurons make up the CNS?

I generally see it written that there are three types of neurons, classified by projection: (1) sensory neurons, (2) interneurons, and (3) motor neurons. Now, in the CNS, I don’t think there would be ...
2
votes
1answer
319 views

Is reproduction intrinsically part of life? [closed]

If all of the characteristics of life are required for something to be defined as living, how can we account people or other life that can not reproduce?
2
votes
2answers
47 views

Why is oxygen and CO2 measured in pressure instead of mmoles/L like other ions?

Na, K, Cl...All measured in mmol/L in plasma. Why is oxygen and CO2 measured in pressure (mmHg)? (I guess it has something to do with them being bound to RBC but I don't know why the difference).
0
votes
1answer
104 views

Why does the Vas Deferens detour over the pubic bone?

I was surprised to learn that the vas deferens detours over the pubic bone instead of taking the obviously more direct path. https://human.biodigital.com/widget?be=u1P&uaid=1ly5V Because I would ...
3
votes
2answers
64 views

Is saturation of olfactory cells able to create a feeling of another odour when it stops?

I'm looking for at least one scientific study about how odours could impact human olfactory system and create some phenomenon that could be loosely compared to retina remanence. As an example, with ...
1
vote
0answers
59 views

Why does sex give people pleasure [closed]

My question is Why does sex give people pleasure? I know that the pituitary gland secretes sex hormones and the sex organs receives the signal. How is it related to dopamine at last? Through ...
-1
votes
0answers
20 views

Does oxyhaemoglobin is less likely to unload oxygen in the presence of 2,3BPG?

Red blood cells may contain a molecule known as 2,3-bisphophoglycerate (2,3BPG). When 2,3BPG binds to haemoglobin a higher partial pressure of oxygen is needed to bring about 50% saturation of ...
0
votes
1answer
79 views

Acrosomal enzymes and the female reproductive tract

My textbook wrote that the reason why acrosomal enzymes are so securely contained within the sperm (thus needing capacitation to facilitate their release) is to prevent any premature release in the ...
12
votes
1answer
8k 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 ...
-3
votes
1answer
59 views

Is it necessary to remove a bullet from the body? [closed]

So here is the proof: William Lawis Pace lived with bullet in his head for many years & even hit 100. However, both in real life and movies, we often see doctors struggling to remove bullets ...
1
vote
1answer
92 views

Which are the last cells of the human body to die?

When somebody dies, which are the last surviving cells of his/her body? Those of hair, nails, or some other obscure but resilient cells? Shedding light on why and how they are so vital might boost ...
3
votes
1answer
56 views

Living on pure glycogen?

I was recently fascinated when I learned about polysaccharides (I am a biology newbie) and was wondering about some of their properties. After doing some googling I was unable to find any information ...
1
vote
1answer
56 views

How do cancers eventually lead to death / other debilitating symptoms? [closed]

With regards to people I know or have read about who live with cancer, most of their symptoms are results of chemotherapy, surgical interventions, etc., which have the goal of eradicating the cancer. ...
1
vote
1answer
30 views

Resting stage of primary oocytes

In my biology textbook, I read that the primary oocyte gets arrested in the early stages of meiosis in prophase I (diplotene stage). I wanted to know why this is so. I searched google, and this ...
2
votes
3answers
7k views

What organs are absolutely needed by the human body?

The title is my question: what organs are absolutely needed (fatal if injured/removed) by the human body and perhaps animals in general? I'm not asking which organs are mechanically replaceable, but ...
0
votes
0answers
20 views

Lyonization and Turner's syndrome

If lyonization is basically inactivation on X chromosome, and Turner's syndrome patients have only one existing X chromosome, what is the difference between healthy women with inactivated X chromosome ...
17
votes
1answer
604 views

How fast can a human run?

I'm a runner (cross country) and I'm always amazed at how fast Olympic sprinters are. There's a lot of hype about those in the 100-meter dash being the fastest in the world, and we're constantly ...
1
vote
1answer
113 views

How can alcohol cause blindness?

Strong alcoholic beverages (e.g. moonshine) are reported to have caused blindness amongst some people. How exactly can alcohol make someone go blind? Is that because different forms of "rubbing" ...
13
votes
3answers
5k views

What is the evolutionary reason behind the fragility of teeth?

Almost all organs in the human body have a rather large threshold within which the organ or tissue is capable of repairing itself using materials supplied by the body, whether it's made from organic ...
3
votes
1answer
2k views

Does a woman contain all the genes needed to make a man?

I know the answer of inverse is at here, but how about this question? I also read this question, can I imply to human that a woman can also contain all the genes needed to make a man? Edit: I ...
4
votes
1answer
8k views

Which blood vessel carries the most impure blood?

There is a question in my Biology textbook: "Which blood vessel in the human body carries most impure blood after few hours of meal." The answer is given as Renal artery. But I think the ...