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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How brain hemorrhage occur?

I want to more about brain hemorrhage. Like a.) Why only some part of brain only gets affected by high blood pressure? Means more than one position bleeds are possible? b.) The artery gets burst or ...
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1answer
57 views

Is it biologically possible for an adult's eye color to change?

Can it be that the adult eye can change color? Specifically my question is about a unilateral color change, such that the color of one eye remains constant, while the other changes color over time. ...
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1answer
69 views

How common is complete heterochromia?

How common is complete heterochromia? (One iris is a different color from the other) Are there any statistics available for this? If no, why not?
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1answer
26 views

Exact location of E. coli in human body

E. coli lives in lower intestine. But exactly where can we find E. coli, and where is there none (or a really small amount) of it? I need the exact names of parts of the lower intestine where we can ...
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T-cells Question

T-cells are important for efficient vaccination since they have: A. T-cell receptor (TCR) B. CD4+ C. CD8+ D. Memory My gut is telling me it's A since the TCR would recognize the antigens but I ...
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0answers
10 views

Is Norepinephrine beta2 adrenomimetic?

I know that it has alpha1, alpha2 and beta1 effects. It has beta2 receptor where epinephrine can effect. However, to say that it is beta adrenomimetic, I am not sure. That is ligand binding beta2 ...
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0answers
6 views

Ephedrine or pseudoephedrine indirectly central alpha2 mimetic?

I started to think this problem by first thinking if the alpha2 mimetism is possible in either case. It seems to be indirectly in either one. Ephedrine seems to have more prominent effect in CNS. ...
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3answers
115 views

Why is it better to drink room temperature water instead of cold water? [on hold]

My teacher told me that drinking water that is room temperature is better for you then drinking cold water, but she did not tell me why that is. I want to know because I often drink cold water (with ...
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2answers
86 views

Like other animals, why humans don't have species & breeds?

Like other animals, why don't humans have species & breeds ? Even my pet dog is one type of breed, but we (humans) lack breeds & species? What is the main reason?
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2answers
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If human eyes watch an area, what's the shape of its capturing shape? Rectangular? Half spherical?

A normal camera can capture a rectangular image. If human eyes watch an area, what's the shape of the captured region? Rectangular? Half-spherical?
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0answers
14 views

How is the loss of blood estimated after trauma? [duplicate]

How do medical professionals measure/estimate/guess the loss of blood after an accident?
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1answer
47 views

Why do people and animals stretch out their bodies and what is causing this behaviour?

I noticed that my cat which is only 6 months old has started stretching its body from time to time. Then I thought that this motion doesn't seem very natural from another cat's viewpoint, so my cat ...
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0answers
18 views

Is it true that there is a finality in nature? [on hold]

Every biologic thing having its own purpose; for example a carnivore flower that attracts a fly to eat it. Or a flower having seeds that spread with the wind. Or the liquid in which the foetus float ...
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0answers
23 views

What's the max speed that humans could run? [duplicate]

Assuming humans could use all of their muscle strength at once, with no need of cooling or energy, how fast could we theoretically run?
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1answer
111 views

Why can you not tickle yourself?

It's the age old question, why can't we tickle ourselves? If you rub your fingers along your skin, sure there's sensation but you don't break down into a laughing fit (at least I don't :P), if someone ...
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0answers
92 views

Evolutionary reasons why you cannot tickle yourself but masturbate

There are obviously good reasons that explain why you cannot tickle yourself (see e.g. here). This got me thinking why it is possible to masturbate... Wouldn't it make more sense to not being able to ...
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1answer
27 views

Safe level of chlorine in water [closed]

Chlorine is usually mixed in water to make it safe for consumption. What is a safe quantity of chlorine that can be consumed? What are the side effects of chlorine and does this include hair loss? ...
4
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1answer
490 views

What are the advantages and disadvantages of being ambidextrous?

What are the advantages and disadvantages of being ambidextrous? We have two hands and we nearly can't use one and this seems like a weakness, and a stupid one when you first think about it. But ...
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1answer
62 views

Any relevant knowledge/studies about voluntary goose bumps

I'm not entirely sure how normal this is, but since I was a child, I've been able to produce myself voluntarily a "chill" sensation that seems to start on my head and traverse the rest of my body, ...
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6answers
3k views

What is the use of eye banks, if eyeball transplants do not exist at present?

Corneas are donated and transplanted, but not the eyeball. I don't understand. What is the purpose of donating a cornea without an eyeball to a blind person?
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0answers
19 views

What would a human body do with an excess of stem cells? [closed]

This question STEMS (WOO starting right off with the puns) from an lack of understanding of stem cells. My naivety tells me that when a stem cell is introduced to the body, "SOMETHING" tells that cell ...
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0answers
49 views

What proportion of salt in water would make it not dehydrate nor hydrate someone?

Drinking sea water can be deadly as it contains too much salt, basically de-hydrating the body. Normal tap water contains little salt and is good for re-hydration. My question: How much salt needs to ...
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0answers
23 views

What is the biological basis of “energy” that extraverted humans draw from social engagements and introverts expend?

This question is related to this question about introverts becoming exhausted after extended social events on cognitive sciences stack exchange. As I read more on the topic of human ...
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1answer
95 views

What are the disadvantages of forbidding flights to and from the African Ebola region?

After looking through the available Stack Exchange sites, this one seems to come closest to the appropriate place to ask... Popular opinion, including my own, is that banning flights to and from the ...
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3answers
22k views

Why do mammalian red blood cells lack a nucleus?

How did the red blood cell in humans get to lose its nucleus (and other organelles)? Does the bone marrow just not put the nucleus in, or is it stripped out at some stage in the construction of the ...
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0answers
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left to right hand eidetic memory affection [closed]

If a child who was left handed is made right handed, will it affect his eidetic memory ? I need to know please. No information from other sources. I tried
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0answers
21 views

How does proximal centriole of human sperm function?

I've read that the human's unfertilized oocyte ( stuck at metaphase 2 of meiosis ) lacks centrioles and that it completes meiosis 2 after fertilization as sperm gives its proximal centriole. Then what ...
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2answers
581 views

Which sex has higher variance of reproductive rate in modern societies - male or females?

Who has a more varied reproduction rate in modern western societies - men or women? The average rate is the same of course, but I wonder which sex have higher variance - higher variance means that ...
2
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1answer
71 views

How are arms different than legs?

Ok, this is a bit of a tangent question, but it came up yesterday and I didn't know the answer: How are arms and legs defined physiologically? For example, we say humans have two arms and two legs, ...
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2answers
124 views

Can human survive falling from 30,000 ft without a chute?

If someone falls 30,000 feet without a parachute; what are the chances of survival if they landed in the water?
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2answers
6k views

Does sour food cause sweating?

While eating sour food or candy, I start to sweat if it's sour enough. My body feels much hotter although my actual temperature is the same, my forehead starts sweating a lot and I feel like it just ...
3
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1answer
28 views

How does the body really react to exposure to the vacuum of space?

I've seen sci-fi movies where the effects the body being unprotected in outer space are wildly different. In one movie, a guy radios for someone who's been ejected into space to breath all the air ...
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1answer
14 views

What is 'independent assortment'?

What is the definition of 'independent assortment'. I tried researching this term but came back with two results: alleles assort themselves independently of different alleles the alignment of ...
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2answers
53 views

How hot can a beverage get without burning the tongue?

What is the maximum temperature that a beverage can be without burning the tongue? I suspect there's a maximum temperature that the surface tissue of a tongue can withstand without being damaged ...
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0answers
26 views

Why does a pacemaker have a negative pulse?

Why is the first phase of the pulse from a pacemaker cathodic?
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1answer
1k views

Why do we have five fingers?

Humans (and other humanoid mammals) have five fingers in each hand. Curious to know, why five? Wouldn't more fingers be more useful? Is there any evidence that it used to be different and natural ...
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1answer
25 views

Clarification on BMI formula

In the BMI formula= (Weight) X 703) / (Height^2) , what does 703 represent? What is a reliable source that I can cite for this answer? weight= lbs height= inches
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3answers
268 views

How does a person get AIDS?

I am inquisitive to know about how a person contracts AIDS. Among the common masses it's still the belief that having sex with multiple partners causes the disease but that is not the case when read ...
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0answers
24 views

if woman could live to the age of 150 at what age would they go through menopause? [closed]

Ive been wondering this for a while, I watch star trek and other geeky stuff (no offense.) but i would like to my question if you could give to me, if humans could live up to 150 of age or past that ...
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1answer
23 views

Does vitamin D form crystals in the blood with calcium and magnesium?

I read on a vitamin-D product (2000NE) that I should not use calcium and magnesium with it, because it can result crystal formation in the blood. I googled, but find anything about this. Is it true? ...
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2answers
23 views

How does the cell regulate different metabolic pathways?

I heard somewhere that cells use different nucleosides bound to triphosphates e.g. ATP, GTP, CTP and other modified compounds: NADH, NADPH to distinguish between different metabolic pathways and so ...
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1answer
32 views

Does the cellular response to every receptor work the same way?

I heard somewhere that activating any receptor results in the same intracellular response (signaling) which involves NF-κB. If that is true, I hardly understand how the cells distinguish between ...
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3answers
2k views

Is there any use of CO₂ in human body?

We all know CO₂ as a waste product of metabolism . Does CO₂ have any helpful role , apart from having a role in pH of blood ?
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1answer
89 views

What is atrial fibrillation?

I am wondering exactly what a-fib is (causes and symptoms). I would really appreciate having a sample of an EKG with it (because in my limited research, I have found it nearly impossible to find just ...
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1answer
35 views

Like size and colour constancy, why does the brain not maintain focus constancy?

I have progressive myopia. I grew up with perfectly normal eyes but slowly started getting myopic. The thing is, my brain knows (or should know) what the world looks like -- it knows that far away ...
2
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1answer
31 views

Relieving pain by massage

How come the pain in our body, primarily due to excessive physical exercises, vanishes after having a massage? What is the mechanism?
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0answers
26 views

How to evolutionary explain menstrural cycles synchronization?

Sorry, I can not indicate the source, but I read that menstrual cycles of women who live in the same house over time sync. Is it true? How does it work?
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1answer
2k views

What are differences between formation of embryonic disc in chick and mammal embryo?

Exam question which got lowest average points in my university: 1/5 average. No markscheme available so my attempt below. I assume that embryonic disk prefers to germ disk such that Formation prefers ...
2
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1answer
31 views

What is the most recent well-attested common ancestor of chimpanzees and humans?

Humans and chimpanzees are related and thus have a most recent common ancestor. Of course pinning down this precise point is essentially impossible, so I'm interested in close ancestors of this most ...
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1answer
34 views

What are studies linking dietary choices over life with probability of reaching higher ages? [on hold]

Are there big studies that link diet and lifestyle choices with the probability of reaching a certain age? What are their conclusions?