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

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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 ...
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1answer
238 views

Are the byproducts of mammalian digestion simply depleted versions of the food or liquid consumed?

When mammals consume food and digest it or drink fluids that are then filtered by their kidneys, are the waste products generated simply depleted versions of what they consumed? Are there other ...
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264 views

What is atrial fibrillation? [closed]

I am wondering exactly what a-fib is (causes and symptoms). I would really appreciate having a sample of an EKG with it (because in my limited research, I have found it nearly impossible to find just ...
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2answers
127 views

Is vision a vestigial sense for deep ocean species?

Sunlight doesn't penetrate beyond a couple of hundred feet from the surface of the ocean. Species that exist at greater depth probably live in a state of perpetual night; yet from a quick google image ...
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1answer
40 views

Do goosebumps always appear in the same spots on the skin?

Often one gets goosebumps when one is cold. I am curious whether the precise location of the goosebumps on, say, one's leg changes from occurrence to occurrence or not? In case if their precise ...
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1answer
91 views

Loss of appetite during fever

It is a well-known phenomenon that sickness like the common flu is often accompanied by reduced appetite. Why do sick people stop eating?
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3answers
294 views

Is there a known glucosepane cross-link breaker?

I read the following on wikipedia: There is, however, no agent known that can break down the most common AGE, glucosepane, which appears 10 to 1,000 times more common in human tissue than any ...
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2answers
158 views

Do people with gout live longer?

Antioxidants reduce damage to tissue (by scavenging the free radicals) and thus may reduce ageing.It is known that Uric acid is a very good antioxidant. People with gout have excess accumulation of ...
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137 views

What is lack in sense of smell called?

People who lack the sense of hearing, vision and speaking are called Deaf, Blind and Mute. But what is the person called if he/she lacks the sense of smell? Is there any case like that?
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2k views

Why Doesn’t Hypercalcemia Cause Muscle Spasms?

If you have more calcium in the cell, wouldn’t more attach to troponin and initiate muscle contraction? Why does hypercalcemia cause muscle weakness instead of spasms?
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528 views

When glucose production is low, the brain begins using ketoacids as energy… how does that work?

Can someone very generally describe how the brain consumes ketoacids/ketone bodies when blood glucose has been completely depleted?
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1answer
379 views

What’s the reason for isovolumic contraction and isovolumic relaxation?

During cardiac cycle, there are two periods in which the heart volume doesn’t change, but there is a change in tension/pressure. It takes about 0.25-0.35 second to achieve this change. I searched in ...
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182 views

What are the factors that control the speed of propagation of neuronal signals?

If we consider an analogy between a wire and a neuron there may be some resemblance between the factors controlling the data flow rate. For example the increased width of wire leads to decreased ...
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4answers
377 views

Why do the humans become sleepy after meals?

I don't know about all the mankind, but I know enough people, who becomes sleepy after their meals. Also, I'm not sure, what kind of food do they consume, but I personally get sleepy almost from any ...
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1answer
3k views

What are the units of Q10 (temperature sensitivity)?

$Q_{10}$ is the increase in a rate (e.g. activity of an enzyme) observed with a 10° temperature increase. According to Wikipedia: ...
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1answer
39 views

How do cold conditions help organ transplants?

Body organs are kept cold in-between explanting them from the donor and implanting them in the new host. How do these cold conditions help organs to stay viable while they haven't fresh blood, energy ...
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1answer
385 views

Hydrogen Peroxide on Open Wounds

I know that H2O2 is a chemical with high oxidative potential. It can deliver nascent oxygen which can destroy bacteria. I understand that open wounds have cells that are dividing at a fast rate to ...
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1answer
87 views

Do human visual functions degenerate due to genetic factors or by external factors?

Does eyesight primarily deteriorate 'naturally' due to genetics (genomic/epigenomic factors), or due to external factors such as normal wear and tear, or disease? By normal wear and tear I include ...
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1answer
3k views

NADH inhibits gluconeogenesis?

I was told in a physiology lecture that alcohol inhibits gluconeogenesis because 'NADH produced from ethanol catabolism leads to product inhibition'. But is NADH not a reactant coenzyme of ...
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1answer
135 views

How does regurgitated food go to the 3rd stomach chamber instead of going to the 1st?

Ruminants are known for their regurgitation of food; the food goes through the 1st and 2nd stomach chambers, then returns to the oral cavity in cuds. The cuds then come back into the stomach, but this ...
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1answer
162 views

How does sepsis affect heart function?

I have intuition that sepsis with infection can cause: spastic functioning of heart during systole heart working spontaneously in snatches during systole atrial fibrillation first contraction of ...
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2answers
201 views

What are the physiological roles of Hydrogen sulfide?

I am thinking why hydrogen sulfide has its effects in the body. For instance, it is one Salmonella's virulence factor. I am not sure if such a balance equations holds H2O + H2S ←→ ... Actually, I ...
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1answer
839 views

Why does caffeine consumption cause one to urinate more?

What is the physiological mechanism behind the diuretic effect of caffeine?
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1answer
78 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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1answer
78 views

Difference in reptile inner ear and otosclerosis

In reptiles, the sound is conducted from the tympanic membrane to the inner ear by a single bone. In the disease otosclerosis the stapes of humans become fused to the other middle ear bones( or to ...
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2answers
96 views

Why we have to damage our muscles to build them?

I know that new muscle cells are made when actin fibers are disrupted. My hypothesis is that muscle mass is limited, from birth, and that nutrients (protein) are only directed to grow muscle when ...
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1answer
582 views

Is the swimming pool water harmful to frogs who jump in? If so, how?

Here is an odd question: Frogs have permeable skin. Indeed, via capillary action, frogs absorb water through their skin. Chlorine is in principle a harmful substance. I am sure what percentage of ...
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1k views

How does Bernoulli’s Principle apply to the cardiovascular system?

Below are graphs which illustrate the cross-sectional area, velocity, and fluid pressure through each vascular segment of the cardiovascular system. It makes sense that velocity and cross-sectional ...
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67 views

Determining how much energy a plant takes in?

I asked a question on WorldBuilding.SE, "Are diamond berries possible?". This led to asking a question on Chemistry.SE about the amount of energy required to burn a 1 ct. diamond (−6.527kJ). The ...
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2answers
4k views

Difference between facilitated diffusion and secondary active transport in cells

Specifically, what is the difference between facilitated diffusion carrier processes (passive transport) and secondary active transport co-transport processes (active transport)? They seem to be the ...
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1answer
75 views

Liver - Regeneration in Cirrhosis

Liver is the most resilient of the human organ (on par with or next to skin). A very interesting experiment on liver regeneration is here. Even if two-thirds of the liver is removed, the remaining ...
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1answer
573 views

Antihistamine's effect on insulin secretion and tiredness

Antihistamines are known to cause tiredness. The essential hormones of the body are insulin (glucose), parathyroid hormone (calcium) and aldosterone (Na-K ATPase, sodium). I am thinking how this ...
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1answer
26 views

Polarized epithelium and localization of ion channels

I'm trying to learn more about polarized epithelial cells of the gut. I am familiar with classic brush border transporters localized to the apical memebrane to facilitate nutrient absorption. I am ...
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1answer
508 views

Is there a maximum pain threshold?

Is there a maximum threshold of pain a Human can experience, beyond which point there is no noticeable difference? I ask this question in part to better understand the definition of pain and its ...
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1answer
154 views

Why does hypertension occur in obstructive sleep apnea?

What is the physiological mechanism behind systemic hypertension resulting from obstructive sleep apnea?
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602 views

How does Humira work when injected into patients with rheumatoid arthritis?

OK, I have rheumatoid arthritis and I've been injecting Humira 2 times a month for the last 8 months. As far as I know rheumatoid arthritis is simply an immune system disorder which makes the immune ...
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52 views

Effect of arteriole dilation on vein

If an arteriole leading to a capillary bed is dilated will the pressure in the vein coming out from the bed decrease ? Will the velocity of blood in the vein change ?
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3k views

What is the genetic basis of blood type (ABO) system?

What is the genetic basis of the A/B/B+/O/etc. blood type system? Are there definitive loci that correspond to each or can multiple different genotypes produce the same antigen profile? Also, is the ...
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1answer
116 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 ...
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1answer
44 views

Doesn't the sarcomere contract during isometric contraction?

During muscle contraction, the lenght of the sarcomere changes, length of myocyte changes and so does the length of muscle. However, if the length of muscle is not changing length as in isometric ...
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1answer
54 views

Does food continue to stay sequential once it is inside my body?

I may be very off on many scientific details here, but I'm always all ears. As far as I understand, any food that is eaten goes to the stomach, gets broke down even further into smaller food ...
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1answer
37 views

classical conditioning paradigm for hippocampal learning

I wanted to know what a suitable classical conditioning experiment would be to analyze learning and memory capabilities in rodent models with respect to hippocampal long-term potentiation. For ...
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1answer
53 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. ...
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1answer
75 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 ...
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2answers
190 views

Electronic cigarettes (e-cigs), any health risks?

Background: An electronic cigarette (e-cig or e-cigarette) is a battery-powered device which simulates tobacco smoking patented in 1963 by Herbert A. Gilbert. It generally uses a heating element ...
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1answer
676 views

What are the highest and lowest possible pH, paCO2 and HCO3 in the blood of living human?

What are the highest and lowest possible values of pH, $paCO_2$, and $HCO_3$ in the (arterial or venous) blood of a living human being?
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2answers
628 views

Correlation between muscle size and absolute strength

Is there a linear connection between muscle size and the power it can produce? If not, why? And what is the true correlation if any, can it be described with an appropriate function? What other ...
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1answer
171 views

Attachment of muscles during molting in insects

Normally, insects' muscles are attached to their exoskeleton but what happens to this attachment when they are moulting? Sorry if this is an extremely silly question but I have wondered about it for ...
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1answer
293 views

Need of Creatinine Phosphate

In muscle cells most of the ATP's phosphate is with creatinine phosphate. So why is the displacement of the phosphate group done ? Is it because creatinine phosphate would give it's phosphate more ...
3
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1answer
172 views

How is olfactory acuity rated/measured?

Acuity of one's sight is rated on the 20/20 scale. An online search appeared to indicate there is no comparable 'standard' to rate olfactory acuity. How is acuity of the olfactory system rated?