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

learn more… | top users | synonyms

21
votes
3answers
4k 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 ...
4
votes
1answer
203 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 ...
29
votes
4answers
67k views

What's the maximum and minimum temperature a human can survive?

This is a question that has been in my mind since I was a kid. I'm not a doctor, nor even a biology student, just a curious person. What is the minimum and maximum temperature a human body can stand ...
3
votes
1answer
103 views

Elevated position effect on recovery times from upper respiratory infections at rest?

In nursing school, they advice for people with upper respiratory infections to be in a slightly elevated position at the head region when sleeping. My intuition of the reason is that the lymphatic ...
9
votes
3answers
206 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 ...
14
votes
2answers
999 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?
5
votes
1answer
933 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, ...
17
votes
3answers
326 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.
16
votes
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 ?
10
votes
1answer
184 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 ...
29
votes
1answer
766 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 ...
12
votes
3answers
168 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 ...
5
votes
2answers
106 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 ...
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 ...
16
votes
3answers
423 views

Are human fetuses more likely to be male? [duplicate]

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
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
votes
1answer
153 views

Relationship between nerves and axons

I just wanted to get a realistic viewpoint of our nervous system. I understand arteries and veins, but I wanted to know how similar our nervous system is to that? I understand we have neurons ...
3
votes
2answers
958 views

Ill effects of urea and NH₃ on metabolism

What exactly does urea do that harms our body? Does it interfere with our cellular processes or disturbs the colloidal onchotic pressure of our blood? I have heard that NH3 damages the brain. What ...
2
votes
1answer
68 views

Fast standing and the heart's insufficient accommodation of the increased venous return

Assume you are 45 minutes on the supine position. Furthermore: you stand all of a sudden and fast and without sympaticus activity. The venous return (smooth musculature of vessels) accommodates ...
-1
votes
2answers
106 views

What is the name of the condition where no pacemaker cells are active in the heart for a short-time?

Assume that the heart is beating, but no pacemaker cells are working for at least 15 seconds. This would be a very long compensatory pause if extrasystole started it. There may be some low frequent ...
10
votes
3answers
864 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 ...
10
votes
1answer
157 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, ...
5
votes
1answer
88 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 ...
5
votes
1answer
141 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 ...
4
votes
1answer
110 views

How can we measure cardiac output?

I could find a way which could find it by body oxygen consumption and there is another way to measure it by injecting drugs — measuring cardiac output by the so-called “indicator dilution method,” a ...
4
votes
1answer
102 views

What is the physiological difference between cortisone and cortisol?

There is only hydrogen bond different. Cortisol is synthesized by our body, while cortisone is given to the patient. Why you cannot give cortisol directly to the patient? I think the reason is ...
4
votes
2answers
332 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 ...
3
votes
1answer
55 views

Mechanisms of bone growth

The length of a bone is caused by growth of hyaline cartilage which is then replaced by bone tissue. How do cells know whether they should grow the hyaline cartilage? What are the key molecules that ...
2
votes
1answer
71 views

What happens during a Raynauds episode?

Raynaud's phenomenon can be a serious health issue, as the blood flow to the extremities, mainly the fingers is compromised, causing fingers to blanche, and then turn blue. Severe Raynaud's can cause ...
1
vote
1answer
58 views

Gastro-intestinal physiology reference

I am a physicist but I have always wanted to understand how my digestion takes place in as much detail as possible. I have no idea about books or reference on the subject of Gastro-intestinal and ...
0
votes
0answers
34 views

Few innervations to blood sugar regulation

Assume you have a case of young female where the intake of 75 grams of pure sugar leads to a rapid peak of blood glucose level (within seconds) plateau phase with very steady blood glucose level ...
0
votes
1answer
23 views

Which ionic channels of Pacemakers can work in very low frequencies in extrasystole?

At frequency 0-3 Hz. Like computer processors which can work at low frequencies and controlling under- and overvoltage. Normal most significant channels are Ca2+ and K+ that are changing. However, I ...
0
votes
0answers
25 views

Laser surgery to stop damaged Sinus node from beating

I am trying to find any publication about laser surgery to stop the damaged sinus node which cannot anymore beat. I could only find publications which modifies SA node function. I am not sure if it ...
13
votes
0answers
2k views

Why do we experience temperatures below 37 degrees Celsius as 'hot'? [duplicate]

We always prefer to be in 20-25° C, although our core temperature is about 37°? Why is our skin temperature lower than our core temperature?
12
votes
3answers
935 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 ...
4
votes
1answer
102 views

Mechanism of Muscle Growth

According to this video (sorry for the poor reference but it represents my level of understanding in physiology), muscle grow as a consequence of repairing micro-lesions. How are these micro-lesions ...
4
votes
2answers
217 views

Where do the 31 spinal nerves start/meet?

Which part of the brain is the first place (from top to bottom) where all 31 pairs of spinal nerves (on each side) meet? Or if they all start at one place - where is that? Nominally, the beginning of ...
4
votes
1answer
134 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?
3
votes
2answers
372 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 ...
2
votes
2answers
94 views

Why can't we defibrillate the heart within 1 minute after ventricular fibrillation by electroshock?

We mostly can defibrillate the heart before 1 min of ventricular fibrillation by electroshock.Then we often can't do defibrillate it with electroshock. What's the reason and What's the best way to ...
2
votes
1answer
44 views

Why do the size of the phase 1 notch vary among cardiac cells?

The size of the phase 1 notch varies among cardiac cells. It is prominent in myocytes in the epicardial and midmyocardial regions of the left ventricular wall and in ventricular Purkinje fibers. ...
2
votes
1answer
45 views

Do Ants have a sense of Direction?

Do ants understand which way is up or down? Could they differentiate between uphill and downhill?
2
votes
2answers
163 views

Can the body of any organism on Earth live without impairment both in vacuum, and within Earth's atmosphere?

I know from reading that a human in vacuum needs a space-suit to survive. Is the body of any organism on Earth capable of living equally in vacuum, and on/below Earth's surface within the ...
1
vote
1answer
52 views

difference between ischemia and oxygen-glucose deprived medium

Ischemia is roughly defined as insufficient blood flow to a specific region of the body and in the literature it is generally considered as causing oxygen and glucose deprivation in the tissue and ...
0
votes
1answer
30 views

Are there any forms of heart failure where cell size decreases?

I think hypertrophy happens in most of the cases. However, I am not sure if hypertrophy always happens. I started to think about wet lungs (pulmonary reason for the left-sided heart failure). Can the ...
0
votes
2answers
413 views

Converting unit/mg or unit/ml into ng/ml, or vice-versa

I am working with the enzyme Cu/Zn Superoxide (SOD1) and i am quantifying them in ng/ml. However, most past studies has SOD1 quantified in unit/mg or unit/ml, and i need to compare the SOD1 level of ...