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

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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 ...
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181 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 ...
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190 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 ...
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138 views

Enlargement of thyroid gland

Why does thyroid gland enlarge both in hypothyroidism and hyperthyroidism? Hypothyroid goitre is due to lack of iodine in diet and hyperthyroid goitre (Exopthalmic goitre, Grave's disease) is due to ...
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377 views

Where do most mutations come from, mitosis or meiosis?

According to this (old) paper there are 10 times more mutations during meiosis than during mitosis. One reason for that is that recombination often causes replication error and therefore mutations. ...
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189 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 ...
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170 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. ...
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33 views

Why do Arctic predators accumulate vitamin A?

Top predators in the Arctic are known to accumulate vitamin A, often to levels that are toxic for human consumption. A 2012 study by Senoo, Imai, et al. found that the livers of several predator ...
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155 views

Why do people in the scientific community use terminology such as renal, hepatic, cardiac instead of kidney, liver and heart? [closed]

Are there differences between renal, hepatic, cardiac and kidney, liver and heart? Is the "jargon" used more commonly because of tradition, or is there some definitive biological basis to it?
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213 views

Why does haemoglobin's affinity to oxygen decrease at high altitudes?

My class 12 NCERT book says, Pg 226 The body compensates low oxygen availability by increasing red blood cell production, decreasing the binding affinity of haemoglobin and by increasing breathing ...
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3k views

The number of nipples (breasts) a species has?

Only mammals have mammaries and mammary glands. What evolutionary factors determines the number of mammaries (nipples/teats/breasts) a species has? Is it always an even number?
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Do women experience more bonding hormones than men after sex?

Does Oxytocin (or any other bonding hormone) increase more so for women than for men after sex? Someone told me that it increases 4-fold for men and 12-fold for women (unconfirmed). Is there any ...
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348 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 ...
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37k views

Why are (some) cats attracted by bleach?

(Sorry if this question is only partly biological) I have noticed that several cats (including the one that keeps sleeping in my house), are fond of the odor of bleach (eau de Javel) and chlorine. ...
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153 views

Question about epinephrine

In my class we were told that adrenaline (or epinephrine) causes vasoconstriction. My question was I had always thought that people took this via an EpiPen when they were having an allergic reaction. ...
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223 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?
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116 views

Does transplanted heart have full sympaticus without medication?

I am reading this and this where I am considering this sentence [N]o baseline parasympathetic innervation [in transplanted heart]. Does this sentence imply that the heart work then in full ...
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141 views

What is the reason behind more severe proteinuria in nephrotic syndrome than in nephritic syndrome?

Why is there less protein loss via urine in case of nephritic syndrome than in case of nephrotic syndrome?
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331 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.
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198 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 ...
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34 views

Do pharmacodynamics and pharmacokinetics of the drug in animals are the same as in human?

I'm trying to understand the purpose of different clinical trial phases, and the following question comes into my mind : Do pharmacodynamics and pharmacokinetics of the drug in animals are the ...
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299 views

How do animals handle light refraction in different media?

For a human, when diving underwater, everything is blurry because of the water's different refractive index compared to that of air, which we are accustomed to. How do animals, like turtles, seals or ...
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4k views

Why does a blood test show ethanol when no alcohol was consumed?

Why would ethanol show up in a blood test if a person had not been drinking alcohol in many years. What are other reasons for showing ethanol?
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3k views

Slow-oxidative fibres vs fast-glycotic fibres

Why do slow oxidative muscle fibres contain more mitochondria compared to fast-glycolytic muscle fibres?
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118 views

Are there any situations in which phenylephrine is preferred to pseudoephedrine?

In the mid 2000s in the US, due to issues of drug enforcement, pseudoephedrine containing medications were brought behind the pharmacy counter and in most cases require ID, and phenylephrine was ...
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42 views

How does the muscle return to its resting state after muscle contraction?

I know that when ADP binds to the myosin head, it moves along and as it does so, it releases the ADP. The ATP attaches to the myosin head and releases the myosin head from the actin filament. Then the ...
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58 views

Unable to identify a muscle of the anterior thorax

I was watching an YouTube Anatomy Video which goes over the major muscles of the anterior superficial thorax. There is a structure present throughout the video which goes unmentioned, and I can't seem ...
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250 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 ...
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81 views

Alternating Ovulation

I have often heard that right and left ovaries alternate in releasing ovum. Is it always true? What controls this rhythm? Is it simply because the other ovary is unresponsive to LH or FSH? If so, ...
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440 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 ...
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322 views

what are the mechanics of sweating?

The causes of sweating aside, i.e. I'm not interested in which and how nerve signals are transmitted to sweat glands. But I would like to read a detailed account on what a sweat gland consists of, ...
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700 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 ...
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171 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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1answer
171 views

Why are some human injections intraperitoneal?

In humans, what benefit do intraperitoneal (IP) injections(old/cheap rabies vaccines, or cancer related injections) offer versus traditional intramuscular injections? For example, where I live, the ...
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271 views

What is the relationship between W, X, Y and P, M retinal ganglion cells?

In Guyton and Hall Textbook of Medical Physiology (12e) the retinal ganglion cells (RGCs) are classified into W, X, and Y types. However, in Gray's Anatomy (40th ed.), RGS are subdivided into midget ...
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176 views

Can carnivores survive on a (processed) vegetarian diet? Why or why not?

There are many differences in for example the digestive system between carnivores, herbivores and omnivores. It seems that in certain kinds of species adaptability with respect to diet is possible. ...
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1answer
291 views

Why mosquito bite is confined to a certain shape?

I think this problem should be asked in a physiology forum rather than biology@ stackex but I'll give it a try. So my question is simple - why a mosquito bite is usually confined to a certain shape ...
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1answer
49 views

What are the molecular mechanisms that make the turtle brain more resistant to hypoxia?

I know that turtle brains, particularly those of individual species that hibernate and burrow are particularly resilient to hypoxia and any tissue damage secondary to a hypoxic event. What are the ...
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394 views

How is ammonia removed from the colon?

“Lactulose is also used to reduce the amount of ammonia in the blood of patients with liver disease. It works by drawing ammonia from the blood into the colon where it is removed from the body.” ...
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2answers
3k 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 ...
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1answer
54 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 ...
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1answer
82 views

What causes anorexia nervorsa?

I've heard of anorexia nervosa being a severe loss of appetite. I'm wondering what causes such disease in humans?
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126 views

What is the impact of stress on the human body?

Can stress trigger any changes in the human body? I'd like to know more about things less commonly known than, for example: sweating and tiredness. What are the long term risks of chronic stress? Do ...
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1k views

How are arms different than legs?

Ok, this is a bit of a tangent question, but it came up yesterday and I didn't know the answer: How are arms and legs defined physiologically? For example, we say humans have two arms and two legs, ...
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606 views

Why do I breathe out of BOTH nostrils?

After reading the question why do I only breathe out of one nostril I realized that breathing out of both isn't common. I have always breathed out of both, and when I get a stuffy nose, or a runny ...
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1answer
98 views

Relationship between mN and mg in vessel contraction studies?

What is the relationship between mN and mg as the units involved to measure the changes in contraction? A tool most widely used is an instrument called myograph. In these exoeriments, either units of ...
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147 views

Why do humans circulate monosaccharides instead of disaccharides as in plants?

Plants transport food mostly in the form of disaccharides like sucrose but humans transport them in the form of a monosaccharide - glucose. What is the reason behind this ?
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73 views

How much can you learn about species variation from a skeleton?

I just read about the discovery of the 1.8-million-year-old human skull in Georgia, and how it suggests that early humans were all one species instead of distinct ones. Would an archaeologist ...
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1answer
2k 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: ...
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300 views

Why apes started to contemplate and become altruistic? [closed]

I was asking this first on philosophy forums, but it is suggested, that answer could be found from evolutionary view of point, so here we go: Again my question raised when thinking of myths, their ...