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

learn more… | top users | synonyms

6
votes
2answers
140 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 ...
3
votes
2answers
683 views

Physiological indicators of happiness and well being

If I understand it correctly, levels of serotonin in the brain can indicate if a person is happy. What other physiological measures indicate happiness or well being for a humans? I am looking for ...
16
votes
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 ...
1
vote
2answers
182 views

What gases are needed for humans to breathe?

I will be beginning a science project about sustaining life on space stations. I already know that pure oxygen is harmful for humans but would $O_2$ + $CO_2$ be enough for humans to breathe in or do ...
2
votes
1answer
911 views

fibroblast cells and fibers

I am interested in fibroblast cells in human arteries. Here are the things that I am not clear at the moment and I could not find any answer from the literature: What are the dimensions of these ...
2
votes
1answer
51 views

Deep diving in mammals

Mammals like seals often dive and can remain under water for more than 70 minutes. How do seals know when is it the time to come up?
0
votes
1answer
50 views

What is a good review article source for Physiology?

I am looking review articles for Physiology. For instance, Physiological explanation of steps of measurement of the metabolism by Douglas-Haldane. There is no section for Physiology or metabolism in ...
2
votes
1answer
256 views

Ammonia smell after physical exercise? What is the explanation? [duplicate]

After exercising vigorously one can sometimes smell ammonia and it feels like it's coming from within the nose actually. There is no indication that others can smell it when I do (i.e. seems to be ...
2
votes
0answers
72 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) ...
4
votes
1answer
317 views

What causes instinctive behaviour?

Some actions, almost behaviour, exist that are common across a species. For instance, based on personal observation, human babies try to taste anything new they encounter until they are a few score ...
7
votes
1answer
197 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 ...
6
votes
1answer
488 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 ...
3
votes
1answer
44 views

Immunity during pregnancy

I have learnt that our immune system distinguishes self from non-self by using MHC. So a mother during pregnancy should also develop antibodies against the fetus as it is also a genetically different ...
2
votes
1answer
402 views

Why is the blood pressure in the superior vena cava during inhalation less than during the exhalation?

For further investigation into the progress of the blood pressure, we will measure a patient's blood pressure in the superior vena cava measured during inhalation and during an exhalation. His heart ...
0
votes
1answer
98 views

Are humans more aggressive during a full moon? [closed]

Is it true that we are more agressive during the night when there is a full moon? If true, could this be a remnant from times where we needed to hunt for our food and so could see more at night when ...
4
votes
1answer
108 views

What are some examples of scaling laws in biology?

I've seen that metabolic rate scales logarithmically as function of mass for many animals over an extremely large span of parameters. What other scaling laws exist at the individual level?
5
votes
1answer
126 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. ...
-3
votes
1answer
318 views

What are the long-term negative effects of going without water/food for a period of time [closed]

There are no good answers anywhere. so asking: this is not about days of survival without water. This is about long-term negative effects induced from not drinking water for at least the mentioned ...
1
vote
0answers
80 views

Why do ion concentrations change with different secretion rates in pancreatic juice?

Why is it that when secretory rate increases in the pancreas the concentration of chloride ions decreases, and the concentration of bicarbonate increases in the production of isotonic NaCl secretion? ...
2
votes
0answers
78 views

Size of classical liver lobule across species

A classical liver lobule is made up of a central vein and the portal triads. A typical human liver weighs around 3 lbs. , while a typical bovine liver weighs around 12 lbs. I was wondering if anyone ...
12
votes
3answers
156 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 ...
10
votes
2answers
353 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 ...
1
vote
1answer
153 views

What is the energy balance of cooking?

If I cook some food, I get apparently several energetic advantages: thermal : the temperature of the food is closer or superior to the temperature of my body or internal organs, so I do not have to ...
5
votes
2answers
422 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 ...
1
vote
1answer
66 views

Is stereo olfactory ability restricted to humans?

Most animals I see around seem to have two nostrils - humans, snakes, birds, fish .. and so on. From reading online I see that 2 nostrils provide a stereo olfactory effect. This stereo effect is ...
4
votes
1answer
128 views

What limits the size of fish compared to marine mammals?

The largest extant fish species is the whale shark (Rhincodon typus). With a length of 13 meters and a mass of about 20-30 metric tons, the whale shark is relatively small compared to the largest ...
2
votes
2answers
332 views

What exothermic reaction distinguishes warm blooded animals?

I would appreciate an answer specifically in the form of an exothermic chemical reaction. Namely, the one primarily responsible for generating heat in warm blooded animals that does not take place in ...
0
votes
2answers
99 views

Is there any evolutionary/physiological advantage to multi-lateral symmetry?

Just wondering ; I get the impression a large number of multicellular organisms are multi-lateral in their physical structure. Why would evolution/mutation have retained multi-lateral symmetry in an ...
2
votes
2answers
157 views

What chemicals can be detected from one's sweat?

This question came to mind after reading this article. The article speaks of inducing sweating to determine by a roundabout fashion the amount of salt therein. I'm no medic but I find myself wondering ...
8
votes
2answers
390 views

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

Why is blood pressure generally higher in more distal arteries?
4
votes
2answers
294 views

Extraretinal photoreception in mammals? [duplicate]

A Finnish firm Valkee sells light-ear-plugs against thing such as jetlag. I asked a researcher in Aalto university how do they really work and he responded ...
6
votes
3answers
3k 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 ...
11
votes
3answers
791 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 ...
3
votes
2answers
311 views

Why is the frog genome so much larger than a fish's?

As we have heard in the summaries of the human ENCODE project, 80 per cent of junk DNA appears to have an essential function. Many fish have a genome with only one tenth the size of a usual vertebrate ...
5
votes
1answer
956 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 ...
9
votes
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
4
votes
1answer
143 views

How does ethanol interact with insulin?

I know that ethanol increases insulin secretion--could someone explain why? All I have found till now is experimental data analyses. I am interested in mechanism of alcohol consumption.
4
votes
1answer
935 views

Conversion rate of topical Retinol to Retinoic Acid (Tretinoin)?

I'm wondering if someone out there has more information than me. Retinoids have well known metabolic pathways in vivo, and it's usually something like: ...
10
votes
1answer
166 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 ...
3
votes
1answer
2k views

Slow-oxidative fibres vs fast-glycotic fibres

Why do slow oxidative muscle fibres contain more mitochondria compared to fast-glycolytic muscle fibres?
6
votes
1answer
303 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 ...
7
votes
1answer
797 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 ...
5
votes
1answer
131 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 ...
3
votes
0answers
48 views

Patch-Clamping Neurons Resources

Are there any lectures available on Patch-Clamping? Were can I find a mathematical model of Patch-Clamp? (that can be easily implemented in matlab). I have found some step-by-step protocols on ...
9
votes
1answer
578 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 ...
8
votes
1answer
191 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 ...
4
votes
1answer
149 views

Is a raised baseline between T and QRS normal in any ECG lead?

Here are excerpts from an unknown ECG lead. I find it weird that the "baseline" changes after the T wave and doesn't return until after the following QRS complex. Is that normal/expected for any lead? ...
1
vote
3answers
85 views

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
votes
1answer
437 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 ...
3
votes
2answers
166 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. ...