Questions tagged [physiology]

The study of the normal function of living organisms and their anatomical parts and the means by which their normal functioning is achieved.

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-1 votes
1 answer
36 views

Membrane Potential Question

Hello, I've come across this question and am slightly confused. The question states that for this scenario the membrane is only permeable to K+, thus would the membrane potential in this state just be ...
-2 votes
1 answer
122 views

How is it known that there are only three macronutrients: proteins carbohydrates and lipids?

It is stated here that in human nutrition, micronutrients are nutrients required generally in less than 100 mg daily quantities whereas macronutrients are required in gram quantities. It is widely ...
22 votes
3 answers
3k views

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?
-2 votes
0 answers
18 views

What happens in aortic valve stenosis?

Normally work done by heart for increasing the velocity of blood is only 1% of total work! In stenosis as the cross section of valve decreases it will cause increase of velocity of blood (Bernoulli’s ...
1 vote
1 answer
64 views

Is it possible to live without iodine? (sea plants, seaweed or fish?)

I’ve come across a few other people asking this question on different forums such as on Quora, and Reddit… With my current understanding, we evolved from sea creatures which is why we still need ...
1 vote
1 answer
51 views

How to calculate the osmolality of Hepes solution?

Here is an excerpt from Kollmann et al. (2020, J. Physiol.): This ring was placed in a recording chamber continuously perfused with 37°C aerated Hepes solution containing (in mM) 136 NaCl, 10 glucose,...
2 votes
2 answers
687 views

How is CO2 and O2 separated in our body during gas exchange?

https://www.msdmanuals.com/home/lung-and-airway-disorders/biology-of-the-lungs-and-airways/exchanging-oxygen-and-carbon-dioxide The image in the above link shows that CO2 and O2 both pass through the ...
0 votes
0 answers
74 views

How do whales swallow food underwater without drowning?

How do whales swallow food underwater without drowning? I know they have a valve that blocks the trachea while the mouth is open and that breathing is made from dorsal or parietal breathing holes or ...
6 votes
1 answer
393 views

What are the three dots (eyes?) on the top of this wasp's head? What species might it be?

I photographed these (unidentified) wasps on a sunny but cool winter day in northern Taiwan because they were conspicuously hanging out on a hand railing and had much lighter coloring than I'd ever ...
29 votes
1 answer
4k views

Why do wasps have "wasp waists"? What's been optimized?

I photographed these (unidentified) wasps on a sunny but cool winter day in northern Taiwan because they were conspicuously hanging out on a hand railing and had much lighter coloring than I'd ever ...
0 votes
1 answer
47 views

Water-soluble vitamins involved in amino acid metabolism in the citric acid cycle

I have never seen anything comprehensively written about the vitamins necessary to metabolize amino acids through the citric acid cycle and gluconeogenesis pathway other than the following diagram ...
0 votes
1 answer
133 views

What is the evidence that women experience a larger cortisol spike than men, when they see domestic clutter?

I'm reading a book "The Organized Mind: Thinking Straight in the Age of Information Overload" by Daniel Levitin. At the beginning of chapter "Organizing our homes" he says that ...
9 votes
2 answers
4k views

What biological constraints are there on how large a spider can grow?

Spiders fascinate me, but what intrigues me the most is just how big some spiders can get, which leads me to my question. What biological constraints (if any) would limit how large a spider could grow,...
0 votes
1 answer
100 views

How do I classify cytotoxicity values, whether a sample is mildly, moderately, or highly cytotoxic?

I used LDH assay for cytotoxicity testing. I have a plant extract which I tested against HepG2 cancer cells. I did three trials, my results were 2%, 6%, and 8% cytotoxicity, respectively. How do I ...
3 votes
0 answers
98 views

Is there a biological determinant for right- or left-handedness?

When I was very young, I was sent by parents to examination where I was told both my hands are dominant in the same way. My parents preferred to make my life easier and chose to focus on my right hand ...
3 votes
2 answers
985 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 votes
2 answers
2k views

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

Why is blood pressure generally higher in more distal arteries?
0 votes
0 answers
22 views

Why both with the hypothalamus in the thyroid-hormone secretion pathway?

The release of thyroid hormones into the blood is controlled by the hypothalamic-pituitary-thyroid (HPT) axis. Briefly: Cell bodies in the paraventricular nucleus of the hypothalamus detect low ...
-1 votes
1 answer
37 views

Why do damaged joints or ligaments experience inflammation? Why do physiotherapists try to stop inflammation as part of the healing process?

I have had the repeated experience of going to physiotherapists with injuries to ligaments or joints and they all expressly aim to reduce inflammation. I don’t understand this. Our mammalian (and ...
1 vote
0 answers
56 views

What happens to the gamma motor neuron during too much contraction of a muscle?

Suppose a muscle is contracting too much, so we need a reflex to stop it from contracting too much. Contraction of a muscle causes the muscle spindle to go slack, hence the Ia axons and II-axons do ...
0 votes
0 answers
20 views

What elements are affected when dehydrated?

I know that the blood vessels constrict and there is a decrease in water in the blood. Are there any other elements that increase or decrease when the human body is dehydrated?
0 votes
1 answer
20 views

Does this explanation hold good even in case of Mitotracker red?

When the fluorescence intensity is higher when the depolarization is high? The more damage to the mitochondria, the more mitochondrial dysfunction and therefore more fluorescence intensity. So, in ...
0 votes
0 answers
15 views

How are on and off bipolar cells of the retina arranged?

In the retina, there are both on and off bipolar cells. But how are they spread out in the retina? Are they so, that there is one of each after one another? Or are there areas where there are clusters ...
10 votes
1 answer
18k views

Upon drinking water for the first time in a long time, why do I sweat?

If I don't drink water for a long period of time (e.g. 10 hours), as during fasting, and then I break the fast by drinking water, I start sweating. Why is this?
10 votes
3 answers
22k 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 ...
0 votes
0 answers
29 views

Will a 5nm diameter uncharged object make it through the renal glomerular filtration apparatus in humans?

Will a 5nm diameter uncharged object make it through the glomerular filtration apparatus in humans? I think that it should as I have read that the smallest fenestrations are about 10-15nm in size and ...
0 votes
1 answer
460 views

Is Haemoglobin a positively charged Sol?

My book NCERT(Class 12, Surface chemistry) claims that hemoglobin is a positively charged sol. The cytosolic pH in human cells is around 7.4, but fluctuates through the cell cycle according to this ...
1 vote
0 answers
31 views

Tardigrade scaling and survival

Tardigrades have attracted the attention of researchers with their amazing endurance. They withstand enormous temperatures, high doses of ionizing radiation, resistant to harsh atmospheric factors and ...
2 votes
1 answer
144 views

What is total body water and why is it inversely proportional to fat content of body?

In my textbook "Physiology" by 'Linda S. Costanzo' its written that total body water is the amount of fluid present in the body. So my question is that is it just the water content it means ...
2 votes
1 answer
91 views

Why is iron transported across membranes in the ferrous form?

Iron in the diet of animals is predominantly in the ferric form, but it must be reduced to the ferric form by a specific ferrireductase before it can be transported across the cell membrane into the ...
5 votes
2 answers
6k 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: $$Q_{10}=\left(\frac{R_2}{R_1}\right)^{{10}/\left({T_2-T_1}\...
5 votes
2 answers
914 views

What causes inhalation during breathing?

I have read here that the two major inhalation muscles are the (1) diaphragm and the (2) external intercostals. Additionally, inhalation can also be caused by (1) expansion of the abdominal cavity, ...
5 votes
1 answer
4k 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 ...
1 vote
1 answer
234 views

Why does hyperventilation make you feel like you need to breathe more?

Calm Clinic claims: "The problem is that hyperventilation makes your body feel like you're not getting enough oxygen. Essentially, it makes you feel like you need to take deeper breaths and take ...
59 votes
10 answers
18k views

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 ...
15 votes
2 answers
5k views

Why do animals excrete excess nitrogen instead of recycling it?

I am aware of the different ways animals excrete excess nitrogen (mainly ammonium, urea, uric acid). My question is: why do we excrete excess nitrogen instead of recycling it? How can we explain that ...
1 vote
1 answer
383 views

What triggers the release of gonadotrophin-releasing hormone with the onset of puberty?

I am interested to know the process of development of puberty. During puberty, when boys/girls reache 12-14 (puberty) years of their age, their hypothalamus releases gonadotropin releasing hormone (...
6 votes
1 answer
215 views

Why does hypercalcemia cause muscle weakness, yet hyperkalemia causes muscle excitation?

The reasoning I've been given is that high extracellular $[K^+]$ increases the $E_v$ of potassium; therefore, membrane potential increases and the threshold for action potentials is more easily ...
0 votes
0 answers
74 views

Do whales really sleep "head down"?

Currently there is a broadcast in German TV (see https://en.wikipedia.org/wiki/The_Swarm_(TV_series)) where there was a scene of multiple whales sleeping in suspended state, vertically heads down. The ...
2 votes
0 answers
111 views

Is there any animal known to produce structures of both keratin and chitin?

I began with thinking about the similarities between keratin in its hardest form (fingernails, horn sheaths) and the chitin that composes the exoskeletons of some few beetles I've seen in my life. To ...
0 votes
0 answers
51 views

If the Z-line is pulled from both sides , how does it move to shorten the sarcomere?

When I was considering muscle contraction as a whole, this issue came to mind. Which side should the Z-line of myofibrils shift to when it is being pulled by actin filaments on both sides to which it ...
0 votes
0 answers
55 views

Confusion regarding the role of the capacitor in the electrical equivalent of a membrane

I am having trouble understanding the electrical equivalent of a cell mebrane as it is shown in this picture taken from Kandel: What I cannot understand is the capacitor in the specific image. Why is ...
13 votes
1 answer
7k views

Do colour-blind people see white?

I know that white colour is perceived on excitation of red, blue and green cones simultaneously. It is also said that a colour-blind person doesn't see a particular colour and just perceives it as a ...
-4 votes
1 answer
11k views

Why are plants classified in living things? [closed]

@Volunteers Beware that I am none of the biological magnates. Nor a philosopher. This is just a sign of curiosity. And, I want only an intuition that enables me to see the difference. As far as I ...
1 vote
0 answers
685 views

Osmosis and hydrostatic pressure

I'm confused about the role of hydrostatic pressure compared to osmotic pressure. Q1:If I have a U-tube with a membrane permeable only to water molecules and equal volumes of water on either side ...
30 votes
3 answers
12k views

Does animal blood, esp. human, really have similar salinity as ocean water, and does that prove anything about evolution?

It is an often-repeated claim that human, and in fact all animal blood is salty because we evolved from aquatic organisms, and that blood has a similar concentration of salts as ocean water, or at ...
1 vote
0 answers
32 views

Through what mechanism does ingesting Saturated Fat (but not Mono unsaturated Fat/PUFA) increase Serum Cholesterol.?

I know that the saturated fats you ingest is broken down in the intestines by the bile acids from liver and then re synthesized as triglycerides after crossing the enterocytes. Then these ...
2 votes
0 answers
170 views

Does all CO2 from the blood leave the body through the respiratory system?

I know that the primary way that CO2 leaves a healthy human’s body from the blood is by diffusing into the lungs during gas exchange and then being exhaled. Is there any other way in which CO2 from ...
4 votes
1 answer
119 views

What is the actual molecular mechanism for muscle relaxation?

A number of my students asked what happens to the sliding filaments when muscles relax. For example, in an individual sarcomere, do all myosin heads release all at once or one/few at a time? More ...
77 votes
2 answers
6k views

Do animals exhibit handedness (paw-ness?) preference?

I have been observing my cat and found that when confronted with an unknown item, she will always use her front left paw to touch it. This has me wondering if animals exhibit handedness like humans ...

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