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

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About the small intestine's Vitamin K absorption and large intestine's Vitamin K absorption

Why in the small intestine does Vitamin K absorb to the lymph, while in the large intestine it absorbs to the blood?
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Physiology of tricuspid and bicuspid(mitral) valves

The tricuspid and bicuspid valves are atrioventricular valves. Both are valves that prevent backflow of blood pumped from the atria to the ventricles. However, the former has 3 "flaps" while the ...
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Skin extra sensitive to heat after burn

I just got my finger burnt (first degree burn $\Rightarrow$ I didn't even bother to bear the wound). It didn't hurt much, even when I pressed the wound. However, when exposed to heat (hot water, but ...
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3answers
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Why does the face turn pale in dangerous situations?

I know what the effects are of a dangerous situation on the brain, i.e., an activation of the hypothalamic-pituitary-adrenal (HPA) axis which eventually results in an increased heart rate and elevated ...
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27 views

What are the effects of diuresis and limited water intake? [on hold]

What are the effects on the kidney when taking a loop diuretic and drinking too little water? Loop diuretics like furosemide cause elimination of water by inhibiting water reabsorption in the nephron ...
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1answer
59 views

How are smell and taste in fish differentiated?

The senses of taste and smell in different fish classes are described as two distinct senses; smell is mediated by the nasal openings, and taste by epithelial taste buds. They are both forms of ...
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1answer
33 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 are classified into W, X, and Y types. However in Gray's Anatomy (40e) they are classified into Midget and Parasol ...
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1answer
1k 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 ...
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1answer
146 views

Dimensionless number for blood volume

Comments from the question How is the blood volume of a living organism measured without killing it? by @Nico discussed that the time of blood recirculation scales with the size of the organism. I was ...
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Why are there no organisms with metal body parts, like weapons, bones, and armour? (Or are there?)

Reading this question, Why are there no wheeled animals?, I wondered why no organisms seem to make use of the tensile and other strengths of metal, as we do in metal tools and constructions. I am ...
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1answer
82 views

How can succinylcholine cause myorelaxation?

I first thought that this is because of prolonged depolarisations. However, I am not sure anymore, because after reading PubChem, the only possible pathways are are Choline agonist. So I would say ...
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1answer
30 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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103 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
101 views

How much heat can a human sustain? [closed]

For how long can a human sustain a temperature of 180 degrees Fahrenheit (82oC) without damage in a confined place? For instance, suppose a person is sitting in a steam-filled room, without external ...
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3answers
68 views

What is the difference between meristem and bud?

Keep reading both terms quite frequently while studying plant physiology. I did some research trying to establish their differences and I learnt that meristems are undifferentiated cells that can ...
4
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1answer
155 views

How efficient is the human body at metabolizing food?

My friend and I were having a discussion over how "efficient" human digestion is. If a human ate a 1000 calorie hamburger, how many of those calories (how much energy) does the body process into ...
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2answers
53 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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1answer
30 views

Why do epithelial cells arrest in response to serum?

Primary epithelial cells, for example human mammary epithelium, fail to proliferate (arrest) in serum-containing medium. Therefore, a common growth medium for epithelium contains pituitary extract ...
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2answers
2k views

Why does an electrical shock freeze up muscles?

Why is it when someone comes into contact with an electrical supply that their body freezes up and is unable to move away from the electrical source? Can someone explain this through a physiological ...
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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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3answers
366 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.
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3answers
190 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. ...
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1answer
72 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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1answer
133 views

Counterintuitive action of Vitamin D?

Vitamin D acts in a way which to me is counterintuitive. It functionally supplemets Parathormone. It in the intestinal tract steps up calcium absorption by altering nuclear gene expression and also ...
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1answer
109 views

What is the convention for log notation in biology?

I'm reading through some oldish (1980s) papers on length-weight relationships in fish and crustaceans. Many report log-log relationships without specifying whether this is natural log, base 10, etc. ...
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2answers
130 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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1answer
96 views

Why is the brain dependent on glucose?

The strict dependence of the (human) brain on glucose has always been puzzling to me. While ketones can substitute for a portion of the brain's energy needs, it cannot substitute completely: blood ...
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1answer
32 views

Does creatine-phosphate (CP) supplementation regenerate NADH?

I have the following facts: It is possible to convert ATP <-> creatine vice-versa. (ref - non scientific) CP supplementation protects against metabolic syndrome. ref1 ref2 Fructose digestion ...
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1answer
64 views

How is ATP involved in muscle contraction?

The sliding filament mechanism as explained by my text does not elaborate on how ATP is involved in the cross bridge binding and contraction process. How does muscle contraction utilize ATP? In my ...
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1answer
24 views

Are there fish with a double circulatory system?

Our courseware materials say there are such fish, but the internet suggests fish only have a single circulatory system. Thanks!
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0answers
38 views

What are those visual and auditory reflex controlled by the midbrain? [closed]

The midbrain is a centre for certain visual and auditory reflexes. But what are those reflexes exactly? My study book says that these reflexes are, e.g., responsible for moving the eyes to view ...
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1answer
79 views

Why do fingers swell during cold winters?

When exercising, tissue in the hands may swell. This may be caused by the muscles generating heat, which leads to blood being pushed to the vessels closest to the surface of your body to dissipate the ...
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1answer
25 views

Where does the exudate comes from during inflammation?

During inflammation transudate and exudate is formed by vessels. I would like to make sure if it comes from arterioles, venules, or both, and the reason why.
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3answers
78 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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1answer
40 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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3answers
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Why is high fructose corn syrup unhealthy?

I understand that high fructose corn syrup was found to have detrimental effects on peoples' health. Why is this so?
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46 views

How many mitotic divisions do haploid cells undergo before fertilization?

Background This question is about human physiology and gametogenesis. A spermatozoid is not necessarily the direct "offspring" of diploid cell. Stated differently, a spermatozoid cell can be the ...
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0answers
58 views

Why can we control our breath rate but not our heart rate? [closed]

Even though we cannot survive for more than few minutes if we stop breathing or if our heart stops, why is it so that our heart beat is controlled involuntarily while breathing can be voluntarily ...
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1answer
111 views

Similarity between a heart attack and a spasm

When someone is having a heart attack, could it be considered , in some situations, a spasm? Below, I have written how I believe the process may work. The heart is basically a muscle working ...
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4answers
770 views

How can we differentiate between respiration and breathing?

I am a student of 10th grade, and I eagerly want to learn biology. What is the difference between respiration and breathing?
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2answers
88 views

What is the effect of persistent hypothermia on cardiac performance?

I define persistent hypothermia in this thread about the mechanisms of persistent hypothermia. The Graph of Katzung et al. in Pharmacology about Heart Failure: I am thinking which parts here are ...
9
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2answers
100 views

Why can good music raise goosebumps?

Listening to really good music right now, I was wondering why it raises goosebumps. Is there any physiological reason for this reaction to specific wavelengths or something? EDIT: Due sometimes ...
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2answers
155 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
54 views

Does breathing air containing 3% carbon dioxide gives you a headache?

As far as I know, breathing air containing relatively high levels of CO2 may get you a headache. I also know that CO2 level in the fruit bodies of peppers can reach levels as high as 3% at certain ...
3
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0answers
38 views

How many cells are there in the apical meristematic tissue?

How many cells are there in the apical meristematic tissue? Looking at this picture... , I would tend to think that there are few hundreds cells in the meristem tissue. But I guess this is a ...
3
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1answer
111 views

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

Why is there the need to map these everyday words into another set of words, it seems to complicate matters. Is it done mostly out of tradition or is there some logical basis to it?
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2answers
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Why do men have a higher hematocrit (red blood cell count) than women?

The hematocrit, also known as packed cell volume (PCV) or erythrocyte volume fraction (EVF), is the volume percentage (%) of red blood cells in blood. It is normally 45% for men and 40% for women. ...
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1answer
109 views

Why should or shouldn't we allow the human body to take its natural course? [closed]

For example, when you are sick but don't feel thirsty, this could be due to baroreceptor reflex that is attempting to readjust salt and water balancing. Why shouldn't a patient be left thirsty and ...
4
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1answer
98 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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2answers
120 views

When glucose production is low, the brain turns into keto acid as an energy source, how does this work?

Can someone very generally describe how the brain consumes keto acid when blood sugar has been completely depleted?