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

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Are all healthy animals more likely to defecate near the end of a rest-cycle?

Just what the title states. It stems from observation & personal experience that a person/dog/cat/monkey is more likely to relieve oneself immediately after it wakes up from the peak-sleep cycle ...
6
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1answer
491 views

What causes the characteristic 'gleam' in the eye of a living being?

The title is pretty much what I seek to know. Unless the other person is play-acting, one can often make out the eye of a living person has a shine-of-life to it; a cadaver does not. Similarly the ...
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2answers
192 views

Why is most tissue cellular?

Most tissue is comprised of cells. Why? It would seem inefficient to have so many individual nucleus, membranes, etc.? Specifically: Not all tissue is cellular. Much tissue is extracellular matrix. ...
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1answer
328 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 ...
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2answers
355 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?
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1answer
784 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 ...
7
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1answer
341 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 ...
8
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3answers
569 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?
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2answers
213 views

Is consuming sugar with food as beneficial as consuming glucose (~half of the amount of sugar)?

A few years back I heard at biology class that sugar's molecule consists of half the number of elements of a glucose molecule. So not counting the energy needed to transform two sugar molecules in one ...
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3answers
260 views

Biological Pathway of Lipid Hypothesis

I've read a lot on both sides of the debate of low carb vs low fat diets trying to make some sense of what is being proposed. The lipid hypothesis runs roughly along the lines that we have lots of ...
4
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1answer
165 views

Is there a way for a 19th century scientist to prove that the octopus doesn't revive?

Say a sophiscated scientist in the 19th century noted that applying soy sauce on a dead octopus leads to movement of the legs, as a result of the voltage differences resulting from the salt in the soy ...
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3answers
155 views
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0answers
57 views

Physiological or molecular difference before and after sleep?

I know that the details of the process of sleep aren't entirely known, but have always wondered why I feel rested after sleep. Biologically, what differences can be directly observed in the human ...
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2answers
372 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 ...
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1answer
2k views

What is the “lifecycle” of an average eschar and what types of cells are involved in each stage?

(after some deliberation in the comments, I've decided to make the question more general) An eschar or "dry scab" often forms at a site of injury over a large cut or sore. It seems as though the ...
3
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1answer
48 views

Is there such thing as “biological cycles” of activity/performance/etc in mammals?

I'm looking for some information about the cycles of increased/decreased activity, mental performance or endurance that are related to a mammal's age and the time of a season. First of all, I'm not ...
17
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2answers
342 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 ...
4
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1answer
176 views

Negative feedback in the fructose metabolism in liver

What happens in liver when large amount of fructose is consumed? I vaguely remember my biochemistry lecturer telling us that the enzymes that process fructose in the liver does not have negative ...
5
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1answer
1k views

Do hot drinks cool you down?

It is quite the old wives tale that drinking a hot drink cools you down. If you don't really think about it it does seem somewhat logical: increasing temperature will cause your body to try and cool ...
6
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1answer
419 views

Is it purely the nervous system causing vaginal lubrication (arousal)?

My girlfriend was watching some documentary on TLC about a paralyzed woman getting pregnant. I believe that woman still has some feeling, as she spoke about feeling the effects of a bladder ...
6
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1answer
771 views

What happens to a human body once a sugary snack is consumed?

I'm looking to understand the effects of sugary snacks and/or drinks on a human body. I'm particularly interested in the timing of the ingestion versus various hormonal levels that may be circadian in ...
5
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1answer
956 views

The genetic and physiological origins of laughter?

This Wikipedia article defines laughter in many terms, such as... "a visual expression of happiness, or an inward feeling of joy" and "a part of human behavior regulated by the brain, ...
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 ...
17
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3answers
331 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.
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0answers
109 views

Dimensionless number for blood volume

Comments from the question How is the blood volume of a living organism measured without killing it? by @Nico discussed that the time of blood recirculation scales with the size of the organism. I was ...
10
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1answer
158 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, ...
12
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2answers
520 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 ...
11
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1answer
109 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 ...
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1answer
193 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 ...
14
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1answer
2k 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 ...
4
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1answer
444 views

Does Amphibian embryo's blastocoel become a primitive yolk sac without yolk?

The mammalian blastocoel becomes yolk sac without yolk according to my professor. I have not found any evidence that such a thing happens in amphibians like frog. I need to be able to compare and ...
6
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2answers
563 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 ...
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, ...
7
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1answer
178 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. ...
3
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1answer
104 views

Are ectopic beats considered sinus rhythm for pNN50 purposes?

One quantification of the heart rate variability of an ECG is pNNx, i.e. the proportion of consecutive NN distances that differ by at least 50 ms. When a premature beat occurs, the preceding and ...
7
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1answer
225 views

Are cerebellar basket and stellate neurons actually different cell types?

The title more or less says it all, but to contextualise a bit: Cerebellar molecular layer interneurons have been classified, probably since Cajal, into the basket cells, which synapse onto the soma ...