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

learn more… | top users | synonyms

7
votes
1answer
61k views

What causes random long white body hairs?

I'm sure many of you have experienced this - you scratch your back or brush your hand over your arm and find a ridiculously long thin white hair, sometimes as long as 3 or 4 inches. I know a few ...
7
votes
1answer
852 views

What really happens when a body is tired?

This may be anecdotal; please feel free to vote to close. After staying awake for an extended duration, I usually find myself having to take extra effort to focus my eyes on an object. Similarly ...
7
votes
1answer
201 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 ...
7
votes
1answer
200 views

Why are some menstrual cycles irregular?

A friend of mine asked me this today, and I didn't know. I remember studying the menstrual cycle a few years ago, but I can't remember the details (other than it was very hormone-related), and so I ...
7
votes
3answers
170 views

How does one maintain balance sleepwalking?

Anectodal. Feel free to shoot it down. Walking is an acquired skill; As far as I'm concerned exhaustion causes disorientation. Even after waking up it sometimes takes a second or so to get balanced. ...
6
votes
2answers
1k views

Do women have testosterone?

In a documentary on fitness I saw it was stated that women can't get big like men because of their low concentration of testosterone. If it is true that women have testosterone, where is it made? Why ...
6
votes
1answer
457 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 ...
6
votes
3answers
4k views

Why does having cold hands hurt?

(1). Why does having cold hands create a painful sensation? Is it a physical effect, maybe a protection mechanism from evolution? (2). Why, if one's hands are cold, does it feel as if they are more ...
6
votes
2answers
121 views

Does muscle get bigger by increase in size of individual cells or increase in number?

Somewhere in the back of my mind, I have the claim that a muscle never increases its amount of cells but, if the muscle gets bigger, it's simply because individual cells get bigger. The book Anatomy ...
6
votes
1answer
386 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
votes
1answer
5k views

What is the normal duration of human sexual intercourse?

Wikipedia is saying: Men's typical ejaculatory latency is approximately 4–8 minutes How the researchers measured this? How did they know if the test subjects weren't suffering from premature ...
6
votes
1answer
553 views

Cat purring: What are some possible underlying mechanisms behind purring and bone remodeling and formation?

http://www.scientificamerican.com/article.cfm?id=why-do-cats-purr The article above says that cats purr mostly when they're wounded or under duress. They hypothesis that cats purring leads to ...
6
votes
2answers
154 views

Would muscle fatigue still occur if aerobic conditions for a working muscle is maintained?

Put another way if the muscle is given everything it needs to contract and do work will it ever get tired or have a reduction in energy efficiency? As far as I understand muscles depend upon a ...
6
votes
1answer
180 views

Understanding Membrane / Resting Potential from the perspective of ions?

From wikipedia article RESTING potential: "there is no actual measurable charge excess in either side. That occurs because the effect of charge on electrochemical potential is hugely greater than ...
6
votes
2answers
521 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 ...
6
votes
1answer
125 views

Task-dependent “reversed” handedness: why use left hand for some tasks? How is it controlled by the brain?

I am right-handed. Which means that when I hammer down a nail, I hold the nail in my left hand, with which I can hold it straight and at a controlled position. This is true in situations where the ...
6
votes
3answers
97 views

Why do I feel funny in my tummy when riding a virtual roller coaster?

I've ridden a virtual roller coaster on an Oculus Rift. I felt tension as I went up to the top, but more interestingly I actually felt my stomach drop when I went down the steep drop on the other ...
6
votes
1answer
704 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 ...
6
votes
1answer
495 views

Why does it hurt more when you touch a nerve directly?

I am not a biologist nor know much about biology (so please explain in layman's terms) however I have always been curious as to why this is. What causes the difference in pain between touching an ...
6
votes
3answers
133 views

What gaseous substances do humans emit?

Other than CO₂ and Methane what other gases do humans produce or emit? For example, does skin decomposition, or aerobic respiration emit any special gases that people don't normally realize or know ...
6
votes
1answer
322 views

Can I estimate leaf temperature from air temperature? What other information would be required?

Physiological measurements such as respiration rate and assimilation rate depend on temperature. Most papers report tissue temperature (e.g. leaf temperature for leaf measurements), although some ...
6
votes
2answers
129 views

What type of force holds my body rigid & doesn't make it collapse?

My query is that as atoms & its molecules have inter & intra molecular forces,like that only what type of force keeps the cells bonded to each other & prevent it from collapsing ever ...
6
votes
1answer
102 views

Disproportion in cranial nerve innervation?

The cranial nerve innervation is highly disproportionate, as far as humans are concerned. I am not sure of the advantage of being innervated by cranial nerve versus being innervated by a normal ...
6
votes
1answer
284 views

Why is membrane potential not zero at equilibrium?

For the squid giant axon, the membrane potential computed by the Goldman equation is -60mV. And the Nernst potentials are (the differences between the K+ and the Na+'s Nernst potential and the ...
6
votes
1answer
166 views

How is hibernation/aestivation different from anesthesia?

How do hibernation/aestivation happen? I read on wikipedia that a squirrel injected with the body fluids of a hibernating fellow is more prone to hibernation. If hibernation/aestivation are driven ...
6
votes
2answers
92 views

Why does anxiety cause diarrhea or constipation?

Anxiety sometimes cause diarrhea, sometimes constipation, and sometimes both. It's interesting because it seems their underlying neurophysiology is somehow different. What are underlying physiological ...
5
votes
3answers
141 views

Is it possible to have life in vacuum?

I just got struck by curiosity now: Intuition says no, but I've never had confirmation of it.
5
votes
1answer
839 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, ...
5
votes
1answer
137 views

What protocol does the nervous system use?

I just read How does an inhibitory synapse communicate to the cell body of a neuron? and found myself asking this question ... hopefully I'm not asking the same thing Any body possessed of a nervous ...
5
votes
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 ...
5
votes
2answers
80 views

Why do small organisms make faster movements than big organisms?

I hesitated to ask this question because it seems so obvious and intuitive. However, I am not able to explain this tendency. Background It seems to me that small organisms make faster movements than ...
5
votes
1answer
92 views

By what mechanism can hypoglycemia induce fainting?

Hypoglycemia (Low blood sugar) is said to be among the potential causes of human-faintings. I was wondering by which mechanism this happens. Google search results are abundant; there are lists of ...
5
votes
1answer
116 views

Would my hands sweat this much if I wasn't wearing gloves?

I've wondered about this for a long time, and hopefully someone here has a reasonable answer. I'm a cell and molecular biologist, and much of my time at the bench is spent wearing (usually nitrile) ...
5
votes
1answer
255 views

Skeletal muscles in clam

Although skeletal muscle fatigues fairly rapidly, clams have a protein called paramyosin that allows them to sustain contractions for up to a month. What might be the role of paramyosin at the ...
5
votes
1answer
1k views

How much gas is exchanged in one human breath?

When we breathe, our lungs absorb a portion of the oxygen in the air, and replace it with some amount of carbon dioxide and water vapor. Typically, how much $O_2$ (in grams, milliliters, or moles for ...
5
votes
3answers
146 views

Do dogs have something different about their physiology that allows them to pant without hyperventilating?

I was wondering this as I considered how effective panting would be for humans as a means of cooling.
5
votes
2answers
73 views

How do diving marine mammals avoid decompression sickness?

How do marine mammals, whose very survival depends on regular diving, manage to avoid decompression sickness or "the bends?" Do they, indeed, avoid it?
5
votes
2answers
9k views

What could cause hairs to gray at the tips but not the roots?

I have noticed that some of my sporadic gray hairs are gray at the tip side but oddly, not near the roots. Some are even only gray in the middle. I find all of this very counter intuitive, and I ...
5
votes
2answers
466 views

What metabolic activities are performed by a developing human fetus's liver?

I understand that organ function varies with the stages of development. Does a fetal liver EVER perform lipogenesis, gluconeogenesis, make bile, etc? Or does it only begin performing these actions ...
5
votes
1answer
36 views

Components of the concept of Developmental Noise?

Developmental noise is a concept that correspond to the amount of possible phenotypic variance of a given genotype in a given environment. Intrinsic noise (aka Cellular noise) is a component of ...
5
votes
3answers
251 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 ...
5
votes
1answer
47 views

Examples of genes involved in plastic responses

Adaptive plasticity involves sensing the environment and responding adaptively to it. Intuitively, I would think that this process may ask for a more or less complex genetic machinery of regulation of ...
5
votes
1answer
71 views

How does a Na+/H+ antiporter drive osmosis in this “osmotic motor”?

This recent paper in Cell describes a cancer cell using osmotic pressure to move in confined spaces. The cell preferentially inserts Na+/H+ antiporters in the leading membrane. I want someone to ...
5
votes
1answer
27 views

How does anadromous fish physiology “know” to switch from salt to freshwater and back?

What mechanism allows anadromous fish (like salmon) to switch from salt to fresh water and back? How does the fish "know" to switch its physiology and do other fish possess the biochemical machinery ...
5
votes
1answer
79 views

Competition for mates in sea horses

This source here ...research has shown that it is STILL the males that compete for females. says that male sea horses compete for mates but this source here Females exhibit a ...
5
votes
1answer
132 views

functional hypocholesterolemia due to very high HDL or low LDL?

Nutritional and medical recommendations about cholesterol seem to focus exclusively on hypercholesterolemia, and as such, they provide only a maximum desirable level for LDL and a minimum for HDL. ...
4
votes
1answer
174 views

Body size, what are the evolutionary trade-offs?

Background Considering just the "Kingdom Animalia" branch of organisms. It is clear that bigger does not necessarily mean better - there is large variation in body size... From the 94 µm long ...
4
votes
3answers
134 views

How does strength of a pulse related to EKG(ECG)?

There are variabilities in the heart rate as well as strength of heartbeats. I want to know if one can predict which heartbeat will be strong or weak based on the corresponding EKG/ECG signal. I am ...
4
votes
2answers
66 views

Is the empty GI tract a hollow tube with air inside, or is it generally collapsed until food is eaten?

I have heard that "air in the GI tract" results in flatulence and burping etc, however I initially assumed that the "empty" GI tract was a hollow tube filled with air anyway. So on an empty stomach ...
4
votes
1answer
356 views

How does a pine cone open?

When a pine cone is wet, it remains closed. However, when it's dry it opens again. From the perspective of physics or biomechanics, what is the mechanism that allows a pine cone to open and close as ...