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
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1answer
146 views

Can humans live without their right atrium?

The right atrium is one of four chambers (two atria and two ventricles) in the hearts of mammals (including humans) and archosaurs (which include birds and crocodilians). It receives deoxygenated ...
13
votes
3answers
2k views

Why does hair grow after trimming but remains at a constant length after a while?

Some hair especially body hair regrows after trimming but stops growing after a while. What is the mechanism behind control of hair growth and how is the length limit determined?
4
votes
2answers
263 views

What do biologists mean when they use the term “biological distance”?

Here is its usage. "there is sufficient genetic control to make nonmetric traits useful in anthropological work, and such variables have successfully assigned individuals from distinct geographic ...
9
votes
3answers
366 views

Why did humans become bipedal?

Somewhere in evolutionary history homo started walking upright and became bipedal. You hear these hypotheses that, by walking upright, they could see better across the grassy savannas to escape ...
3
votes
2answers
92 views

How do humans perceive time?

We can see length, and other physical quantities. We can perceive through our other senses like (temperature through thermoreceptors, weight through pressure receptors etc.). But how do we "sense" ...
2
votes
1answer
54 views

How does the genetic material differ between dizygotic twins and ordinary siblings?

I am going to give a rough presentation on twin studies. The terms heritability and concordance are included already, but I struggle with understanding the difference of the genetic material of ...
3
votes
1answer
115 views

Fecundity per woman in early humans

The average fecundity per woman varies a lot from country to country. I call average fecundity per woman the average number of born children per woman. In Homo sapiens, what was the average fecundity ...
4
votes
1answer
99 views

Miscarriage in early humans

Today, about 10 to 20 percent of known pregnancy end in miscarriage. Pregnancy is a biological process that has been very well studied by medicine. As a result, modern medicine helps a lot to prevent ...
5
votes
1answer
63 views

Survival curve in early humans

The survival curve/function describes the probability of a given individual to survive to age $x$. In humans, today's survival function is very much influenced by medicine. This leads me to wonder ...
5
votes
3answers
162 views

Which fruit compounds affect the speed of fructose absorption?

Blood fructose levels are not regulated by insulin in the human body. This means that the body absorbs pure fructose very fast, and it raises the blood fructose levels rapidly. Do fruits/ vegetation ...
0
votes
2answers
140 views

What triggers programmed cell death in humans (from outside the cell)?

What triggers programmed cell death in humans? Is it decided by the brain (for the entire body)? Or is it a local decision of a cell by its environment? Something else? I realize that there might be ...
0
votes
0answers
8 views

awakening effects of light

I tried reading by light from a neighbouring room and felt sleepier than if my own lights were on. Is there a formula for the intensity of light vs physiological preparation for sleep(calcium, ...
5
votes
1answer
148 views

What's the worst that can happen from too much sleep deprivation? Can you die?

It is well known that sleep deprivation causes considerable discomfort in humans (and has even used as a form of torture), but nevertheless there have been people who went through protracted sleep ...
2
votes
1answer
22 views

Relative sweetness

I have noticed that when I eat something sweet, then afterwards, I eat something else that is sweet, the second sweet food is not as sweet as it usually is. I am pretty sure many others have a similar ...
4
votes
1answer
295 views

Besides hemoglobin, what proteins are present in red blood cells?

I knew that mature red blood cells (RBCs) lacked nuclei, but I wasn't aware until just now that they also lacked ribosomes and mitochondria. Most cells in the human body all contain a common laundry ...
8
votes
2answers
216 views

Why don't we see turbulence in the aorta even in normal situations?

I read about the Windkessel effect. Then I read about pulse pressure waves getting reflected from the periphery. If the pulse pressure wave is reflected during diastole and at the same time blood is ...
9
votes
1answer
928 views

What's the smallest size a human eye can see?

During a biology experiment at school, where we would look at waterweeds under a microscope, my teacher said something about that it's impossible for the human eye to see the cells without a ...
2
votes
2answers
55 views

Are we more/less resistant to infectious diseases during an allergic reaction?

To my understanding, an allergic response is a non-adaptive response of the immune system to some molecule. The molecule in question is therefore "thought by the immune system" to be infectious ...
6
votes
1answer
99 views

When are a female's eggs created?

Since a human woman is born with a set number of eggs, and meiosis is the process by which sex cells are produced, would meiosis in a woman happen before she is born or soon after she was born? If ...
3
votes
1answer
285 views

Why does our voice change when we get affected by cold or cough?

Why does our voice change when we get affected by cold or cough? I observed the voice change thing in so many people including me.
1
vote
1answer
47 views

Specialist evaluation for people aged under 40 years with stage 1 hypertension

Reading the NICE clinical guideline for Hypertension it says... For people aged under 40 years with stage 1 hypertension and no evidence of target organ damage, cardiovascular disease, renal ...
0
votes
1answer
42 views

Spironolactone's role with adrenergic agents in heart failure?

I am studying the treatment plan of adrenergic agents for heart failure. Then, in the group discussion, spironolactone was included. But I cannot understand how it is relevant when considering ...
2
votes
2answers
2k views

Can I drink warm/hot tap water? [closed]

I live in Canada and tap water is drinkable, as a matter of fact, the government puts a little bit of flouride in the tap water so it cleans your teeth. My wife and mom always tells me not to drink ...
1
vote
0answers
487 views

Physiologically, how can stress/anxiety cause neuropathy?

According to the Mayo Clinic, stress/anxiety can cause "pins and needles" (neuropathy) sensations all over the body. But how can this be? My understanding of the sensory pathway is that sensory ...
1
vote
1answer
99 views

Can signals travel “backwards” in the sensory pathway?

My understanding of the "sensory pathway" is that its a linear, directional pipeline as follows: Nerves (fire various signals depending on the type of sensors they are) Fibers (transmit signals from ...
1
vote
1answer
53 views

How and where do nerves share pathways to the brain?

I am interested in understanding how pain receptors send signals to the somatosensory cortex (the part of the brain that registers various nerve signals such as pain, presure, temperatures, etc). ...
1
vote
0answers
27 views

Would blue light be effective to help average people when sunsets come much earlier in the day?

I know people with SAD (Seasonal Affective Disorder) benefit from blue light in the winter as night-time comes much earlier (in the UK, sunset is around 4pm in December, compared to 9pm in June). ...
1
vote
1answer
77 views

What specific sensory nerves act as receptors for “pins and needles” (neuropathy)?

According to this excellent answer, the difference between "pain" and "pins and needles" (neuropathy) is that different receptors (sensory nerves) trigger in reaction to different stimuli. Different ...
4
votes
1answer
112 views

Circulating factors affecting human health/longevity

Circulating factors present in young mice have been shown to promote rejuvenation of aged mice, suggesting that tissues have inherent capabilities to regenerate, and circulating factors may be ...
0
votes
0answers
33 views

Maximum heart rate increase/decrease while physically active [duplicate]

I'm a computer scientist and implementing a heart-rate monitor for physical exercise. While I try to improve my code, I stumbled over the question how fast the heart rate can change within a given ...
8
votes
1answer
184 views

How are bones growing, if bones are not connected to the brain?

If the bones are not connected to the brain, how is their growth controlled? This question is not a duplicate of the question Mechanisms of bone growth, as this question deals with how bone growth is ...
0
votes
1answer
46 views

Effect of Western chicken and GH [closed]

I heard this clause from my teacher one week ago: Chicken are grown in half a year until eaten in Baltic countries - Estonia, Latvia and Lithuania, for instance, [probably in other parts of ...
0
votes
1answer
448 views

Can swallowed fingermails, hair, or skin get caught in your appendix? [closed]

There is a common saying in my place: If you eat your skin, hair or nails, it will be deposited in the cecal (Vermiform) appendix, and can cause appendicitis. (This is mostly told to children to ...
1
vote
0answers
47 views

Cigarette consumption dose-response function WRT health outcomes

I'm curious how health risks (mortality, lifetime probability of cancer, etc) change with cigarette consumption. Specifically, treatring cigarette consumption like a continuous variable, rather than ...
3
votes
2answers
63 views

Hydrophobia Outside of Rabies?

RELATED: Why does rabies cause hydrophobia? Agony, Hydrophobia and viruses in the light of evolutionary principles Has hydrophobia been found outside of rabies? I have only seen it ...
0
votes
1answer
33 views

Deeper Learning in Physiology? [closed]

I am a Pharmacology and Toxicology major at a large state school. I was only required to take physics I and II. (algebra based) At first I thought that was fine, but I soon began to realize that I ...
8
votes
1answer
458 views

How does the cornea breathe during sleep?

The cornea is not supplied with blood vessels and so exchanges gases directly with the atmosphere. So how does it breathe during sleep when our eyes are closed?
7
votes
1answer
2k views

Can a human acquire a memory of an animal? [closed]

I would like to know if it's possible for a human to acquire an animal memory. I mean, animals store their memories in their brain, right? And so do we, humans, store our memory. So, is it possible ...
5
votes
1answer
105 views

Effect of closed eyes on balance?

Suppose you want to stand on one leg. Doing it eyes open is not that difficult, but doing it eyes closed seems to be difficult. Why?
8
votes
1answer
671 views

Do the right-handed people tend to use the right side teeth of their jaw to chew food more often than the left-handed people?

And vice versa, do the left-handed people tend to use the left side teeth of their jaw to chew food more often than the right-handed people?Or the frequency of food chewing distribute fairly to both ...
2
votes
1answer
163 views

Why can't people talk while inhaling?

Why do we have to exhale in order to talk? From looking on Wikipedia, it seems like it has something to do with the glottis, but I'm not clear on the mechanism that makes speech sound so different ...
1
vote
1answer
44 views

Anesthetics, specifically inhaled anesthetics

I have had a look at previous inhaled anesthetics and many of them appear to be fluorocarbons. What could be the mechanism behind fluorine's anesthetic properties? Is it the specific bonding pattern ...
9
votes
3answers
382 views

What causes feeling of feet falling asleep to be delayed?

This answer explains the sensation of extremities "falling asleep" as a result of sustained pressure on a nerve. The answer links to an external web page that says that the feeling "quickly goes away ...
0
votes
1answer
34 views

How can Pyridostigmine have the indication of Myasthenia?

I am thinking how pyridostigmine can be used in the treatment of myasthenia gravis. Its similar compound (neostigmine) is also anticholine esterase. This compound has the indication of myasthenia ...
0
votes
1answer
109 views

How does anger relate to blood pressure?

Anger is an emotion generated by neural processes in the brain and is associated with elevated blood pressure. How can an emotion, which is totally related to brain, result in blood pressure changes?
12
votes
2answers
2k views

How was birth control realized in ancient days? [closed]

In ancient days, there were no birth control methods like condoms or contraceptive pills available. How did they control pregnancy?
2
votes
1answer
94 views

How to manage fat-gluten oxidation in celiac disease?

Assume you have been in non-gluten diet 20 years. You built mass 8 mass with substances containing gluten (endogenous gluten stored in fat). Then, celiac disease is diagnosed. You have been 3 ...
-1
votes
1answer
59 views

To understand side-effects for nebivolol's beta1 selective pathway in PubChem? [closed]

Assume you have a drug nebivolol. When nebivolol is used as beta1 selective drug, beta2 is mostly for side effects, but this is not clear from PubChem. I do not know any cases where nebivolol is used ...
1
vote
1answer
47 views

Clonidine's adrenonergic nature?

I am little confused here. I used the term adrenoagonist and sympatholytic to describe the compound. However, my teacher says that the correct term here is adrenomimetic -term. My understanding of ...
3
votes
1answer
758 views

After vasectomy, where does the sperm go?

After vasectomy, where does the sperm go? Vasectomy Procedure cuts only vas deferens, But Our Testes still produces sperm, if there is no output for sperm, where does it go?