The study of the normal function of living organisms and the means by which it is achieved.

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29
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1answer
719 views

What is itching?

What exactly at the molecular level is itching? What physiological function does itching serve, if any? I cant remember the reference but a PLCb3 null mice lost the itch phenotype, so presumably it is ...
21
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3answers
3k views

What actually happens when my leg 'falls asleep'?

Most people have experienced the temporary loss of feeling and tingling in their leg resulting from sitting in an abnormal position for a short while. Usually you get a loss of feeling in your leg ...
18
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3answers
987 views

Why are there no organisms with metal body parts, like weapons, bones, and armour? (Or are there?)

Reading this question, Why are there no wheeled animals?, I wondered why no organisms seem to make use of the tensile and other strengths of metal, as we do in metal tools and constructions. I am ...
17
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3answers
1k views

Do animals exist with an uneven total number of digits?

I recently finished reading Contact by Carl Sagan. In the book they talk about a pattern in the transcendental number like pi or e, and comment that it is found in base 10 or however many fingers the ...
17
votes
2answers
339 views

How does the microbial environment in your gut initiate?

Clearly, a zygote does not harbor any microbes. As it develops, and the alimentary canal tissue is differentiated, I logically assume that there is still no microbial activity in the fetus's gut. I'm ...
17
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2answers
4k 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, ...
17
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1answer
20k views

Why is coffee a laxative?

How does caffeine (or any additional agents) act as a laxative when ingested? I'm interested in the metabolic/signaling pathway.
16
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3answers
301 views

How is the blood volume of a living organism measured without killing it?

How is the blood-volume of an organism measured without killing it? NOTE: The blood-volume of an organism is defined as the total volume of blood present inside that organism.
15
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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 ?
15
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3answers
400 views

Are human fetuses more likely to be male?

Question: From a physiological point of view, when sex is determined in a human fetus, is it equally likely to be male or female? Studies in this area typically measure age at birth, where the data ...
14
votes
1answer
942 views

Why do we get runny noses in the cold?

The most annoying thing for me about being cold is a runny nose. Is there an advantage to having a runny nose when cold? What does having a runny nose achieve?
14
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1answer
1k views

Why do some mammals not have testes in a scrotum?

Coming from an evolutionary approach, Is the only purpose of a scrotum to regulate the temperature of the testes? Knowing all mammals are warm blooded, shouldn't all mammals have testes in a ...
13
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1answer
79 views

What is the mechanism responsible for the periodicity of hiccups?

Hiccups (singultus) are caused by involuntary spasm of the intercostal muscles and diaphragm, producing a sudden inspiration with associated glottic closure. It seems the neurobiology of the reflex ...
12
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3answers
2k views

Why is high fructose corn syrup unhealthy?

I understand that high fructose corn syrup was found to have detrimental effects on peoples' health. Why is this so?
12
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2answers
472 views

Is the 'fluttering feeling' when under stress neurological or physical?

I'm sure that everyone is familiar with the sensation commonly known as "butterflies in the stomach". It is commonly experienced during periods of anxiety or stress (e.g. before high stakes job ...
12
votes
2answers
2k views

How do insects breathe?

Do ants even breathe? If they don't, how do they stay alive? On what resources do they depend upon to stay alive? How are they different form mammals?
12
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2answers
353 views

Is there any reason for the variation in mitochondrial DNA size?

As my textbook An Introduction to Genetic Analysis points out, yeast mitochondrial DNA has approximately 78 kb of genetic data, while the human mitochondrial DNA contains 17 kb. Is there any evolution ...
12
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3answers
158 views

How are long time periods measured in biological systems?

Biological systems are pretty good at measuring fairly long times, for example, menstrual cycles (month), or puberty (years). Counting days or years seems to be implausible, and chemical concentration ...
12
votes
3answers
848 views

How did the huge dinosaurs cope with gravity and loads on bones, etc.?

It's very costly to be a huge animal. Your mass grows in cube when you scale up, but you still only have two/four legs to support the same weight. This increases the pressure that your body needs to ...
11
votes
1answer
104 views

To which distinctions does the term “hymenoptera” refer?

Hymenoptera is an order of insects that includes bees, ants, and wasps. A quick search gives the following etymological analysis of the term hymenoptera. hymen (membrane) + pteron (wing) Does ...
10
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3answers
985 views

Do men have more extreme variations than women?

This question was considered unsuitable for Skeptics and I think it is more suited to BIology than Cognitive Sciences I was reading this article which I found interesting. It is not supported with ...
10
votes
2answers
367 views

Below which temperature human muscles don't work?

When one exposes theirs body parts to cold environment (especially foot and hands), they may be numb, with temporarily blocked both muscles. What is typical body temperature below which human muscles ...
10
votes
1answer
295 views

How can an albatross stay airborne for months?

Albatrosses, of the biological family Diomedeidae, are large seabirds allied to the procellariids, storm-petrels and diving-petrels in the order Procellariiformes. They range widely in the Southern ...
10
votes
1answer
423 views

How long can a bee surive in a jar?

So, some people and I encountered an adventure game where you have a bee in a jar and need to move it from place to place before it suffocates, and someone tried to find out how long a bee would ...
10
votes
1answer
139 views

Were dinosaurs 'hot-blooded' or 'cold-blooded'?

Were dinosaurs hot-blooded or cold-blooded? NOTE: The popular term 'hot-blooded' means having an internally maintained average body temperature, which is generally more than that of the surroundings, ...
10
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1answer
176 views

Does stress physically age our body?

Going by the assumption that stress eventually triggers a flight/fight response, and the subsequent realization that flight/fight puts the body in a system of readiness to use it's available resources ...
9
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2answers
1k views

How do we know the presence of light when our eyes are closed?

Last night I laid on my bed and tried to go to sleep with the light off. I closed my eyes (but hadn't gone to sleep). My younger brother touched the wireless mouse (which had laser) for the laptop. ...
9
votes
4answers
6k views

What is the cause of muscle cramps?

According to wikipedia, muscle cramps are caused by myosin fibers not being able to break free from the actin filaments during contraction, resulting in a prolonged contraction. Obviously a lack of ...
9
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2answers
2k views

How do the lungs act as a sieve to trap blood clots?

Does anyone know? I'm curious to find out as my human anatomy and physiology book doesn't go into much detail on how the lungs function as such
9
votes
1answer
608 views

Is trembling an advantageous response during periods of anxiety?

I originally had planned to ask about whether there was any biological truth in the popular phrase "shivering with fright". However, after doing a fair bit of googling it seems that there is a lot ...
9
votes
1answer
189 views

What are the effects of caffeine on the mammalian circulatory system?

A friend of mine told me an anecdote about his mother, who drank too much caffeine, to the point she became hypotensive and would pass out. Because caffeine acts as a stimulant, I'm assuming the ...
9
votes
3answers
153 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 ...
9
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3answers
741 views

How are our senses dimmed during sleep?

Our senses are not as sensitive during sleep compared to wake. There is an arousal threshold during sleep that only when it is overcome will it wake a person up. My question is how is this arousal ...
8
votes
3answers
523 views

What triggers meiosis in gonadal cells?

What specific biochemical processes are involved in inducing meiosis rather than mitosis? Why are gonadal cells the only cells in the human body which do undergo meiosis?
8
votes
2answers
346 views

Where do the bacteria within the vagina originate from?

I understand that it's feasible the bacteria within the gastrointestinal tract originate from the food we eat and air we breath, but where does this population of microbes originate from?
8
votes
4answers
442 views

Do tall people have more cells?

Within a single species, how does the relative number of cells in the body relate to the relative size of the organism? Let's say we take two humans, one of them is 6 feet tall and the other one is 5 ...
8
votes
2answers
427 views

Why is blood pressure higher the more distal an artery is?

Why is blood pressure generally higher in more distal arteries?
8
votes
1answer
194 views

Does the oxygen concentration equilibrate between red blood cells in the liver sinusoids?

In the sinusoids of the liver, venous blood from the hepatic portal system mixes with arterial blood from the hepatic arteries. Do oxygen molecules move between oxygenated RBCs and non-oxygenated ...
8
votes
1answer
93 views

Why pouring salt in the wounds is painful?

Pouring salt in the wounds is so painful. I am sure you all experienced this. whats happend there?
8
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1answer
1k views

Effects of beer on muscle recovery after exercise

I noticed it several times that when I drink beer (even one bottle) after some heavy workout, the next day my muscles are more stiff than other times, and not the same way... Is it because that ...
7
votes
2answers
905 views

Do snakes get dizzy?

I've seen snakes get twirled around in bags and was just curious if they get dizzy. I have not done any tests because snakes scare me.
7
votes
5answers
326 views

Why is the human body able to repair a broken bone and not a heart muscle?

The human body can repair skin/organ laceration, fractures, even repair nerves - albeit the duration and rate of recovery differ. For instance: The burn scar on my arm from the hot soldering iron ...
7
votes
2answers
1k views

Can human organs be transplanted indefinitely?

I watched this movie, where they rented hearts to people for a year. I wonder if it is possible to transplant a heart indefinitely from person to person, or does the heart have a lifetime? So, do ...
7
votes
3answers
173 views

Where does extra blood come from to fill your muscles during exercise?

Let's say I go to the gym and lift some weights an hour. During this time my arms will grow due to the "pump" -- the extra blood rushing in to feed the muscles. For example, I've measured about 2-3 ...
7
votes
1answer
550 views

Crusty eyes in the morning

Often, after waking up from a night's sleep hard, flaky, pale yellow crystals are deposited around the eyelids (which easily wash off with water). What are these? Why are they yellow? What are they ...
7
votes
1answer
720 views

Does the human ear adapt to noise levels?

I have noticed lately that if I go to sleep, when I have my radio running, it is on lowest volume, I still consider it kind of loud. In the morning, when being on the edge of waking up, I hear the ...
7
votes
1answer
300 views

Do mosquitoes need to pump blood out of the host?

Many species of mosquitoes have bloodsucking females. When they bite a host, do they need to pump? Or does the sheer blood pressure combined with capillary action suffice to make the blood rush into ...
7
votes
1answer
175 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
1answer
70 views

Excretion of monovalent and divalent ions in sharks

I have heard that sharks excrete $\ce{Na+}$ and $\ce{Cl-}$ by their gill surfaces but divalent ions like magnesium are excreted through feces. What could be the reason behind this?
7
votes
2answers
617 views

Can humans transdermally absorb minerals from ocean water, and if so how much?

According to several studies quoted here, chemicals can be absorbed by the skin transdermally, at least under certain conditions. When it comes to elements in seawater like sodium, magnesium, ...