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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Does decompression sickness (the bends) ultimately come from the change in pressure in the lungs, or the actual total ambient pressure over the body?

I am not well versed in physiology, and I've found the literature available to me confusing on this point. Mostly I'm going off of wikipedia, mind you. The article on Decompression Sickness' Mechanism ...
Mia's user avatar
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T-tubules in Muscle Cells

I understand that T-tubules are common to striated muscles such as skeletal and cardiac muscles (with smooth muscle cells having caveolae) but what precisely (if any) is the difference in the T-...
Mason Shah's user avatar
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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 ...
Mason Shah's user avatar
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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 ...
Dr Tenma's user avatar
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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 ...
imrobert's user avatar
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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 ...
Lecifer's user avatar
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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,...
Jasmine's user avatar
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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 ...
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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 ...
uhoh's user avatar
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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 ...
uhoh's user avatar
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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 ...
Blue Various's user avatar
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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 ...
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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 ...
user265902's user avatar
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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 ...
Grazlewacky's user avatar
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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 ...
Maria's user avatar
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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?
Suikurix's user avatar
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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 ...
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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 ...
Nur Ahmed's user avatar
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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 ...
Hypnos Stratagem's user avatar
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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 ...
dtn's user avatar
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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 ...
Lakshya Kumar Singh's user avatar
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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 ...
mathlander's user avatar
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1 answer
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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 ...
Karthikeyan's user avatar
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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 ...
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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 ...
cash999's user avatar
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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 ...
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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 ...
Kani Pen's user avatar
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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 ...
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What happens if we lose voluntary control of our breathing?

Breathing can be controlled voluntarily, even though it is automatic. What happens if a person loses voluntary control of their breathing? How much would it effect day-to-day life? What are its ...
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NMDA receptor depolarization

I learnt that two factors for NMDA receptor channels opening are: 1)Binding of glutamate 2)Depolarization of postsynaptic cell (to remove the Mg+2 block) Given that depolarization starts in axon ...
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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 ...
Sanjay Biswas's user avatar
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Can color-blind people see the effect of combining red, green, and blue light beams?

When combined, red, green, and blue light beams result in white light. This effect is observed by most of us, but can color-blind people also see this effect?
Jordan G's user avatar
4 votes
1 answer
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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 ...
theforestecologist's user avatar
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Electronic properties of neurons [closed]

This is about the electronic properties of neurons. When a signal is sent from 1 part of the brain due to a stimulus,are neurons considered voltage or current sources?
Miss Mulan's user avatar
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1 answer
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Why does a non-functional retinoblastoma protein cause tumours in the cells of the retina specifically?

I know that the name of the protein itself is the retinoblastoma protein - but that's only because the result of a pathogenic variant is retinoblastoma. I'm trying to kind of reverse engineer the name ...
Zuhair Qureshi's user avatar
3 votes
1 answer
140 views

Why does there have to be two muscles to control the size of the pupil?

In dim light, the circular muscles relax and radial muscles contract to allow more light to enter the eye, and vice versa in bright light. Why is there the need to have two muscles when probably the ...
user1039203's user avatar
3 votes
1 answer
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Simultaneous activation of myosin kinase (MLCK) and myosin phosphatase (MLCP)

Reading about smooth muscle cells, I stumbled upon this sentence in Guyton & Hall, Textbook of Medical Physiology (14th ed): When the myosin kinase and myosin phosphatase enzymes are both ...
ConfusedMedStudent's user avatar
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Pulse pressure, vascular physiology

I always though compliance of a vessel is a thing that prevents systolic pressure to goes up a lot and also prevents the diastolic pressure to goes down a lot, and that works because in ...
J122's user avatar
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1 answer
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Solar Celiac Plexus location in body

Where is the Solar (Celiac) Plexus located in relation to the ribcage? I am reading this on the internet, and trying to learn more. "The solar plexus — also called the celiac plexus — is a ...
mattsmith5's user avatar
2 votes
0 answers
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How is the Staverman's reflection coefficient in the Stirling equation determined?

The Stirling equation is expressed as follows $J = Kf ([Pc-Pi] - σ [πc - πi])$ Here, capillary hydrostatic pressure (Pc) and Bowman's space oncotic pressure (πi) favor filtration into the tubule, and ...
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4 votes
1 answer
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Ischemia-induced deploarization in excitable cells

I have read in many sources that ischemia-induced depolarization is due to the opening of ATP-sensitive potassium channels and inactivation of Na/K exchangers [1,2]. However, K-atp channels are inward-...
kljiuklk 1's user avatar
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1 answer
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How does a stimulus causes a voltage change in nerve cell?

I know about the opening of voltage gated sodium channels and then how the membrane becomes depolarized when the rise of potential greater than threshold occurs. But what happens initially after the ...
Kaniksha's user avatar
2 votes
0 answers
27 views

What are the implications for a small bird flying at high altitudes?

Are the aerodynamics of a bird flying at high altitude significantly different than a bird flying at low altitude? I would imagine a bird adapted for low, short flights (such as between bushes and ...
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Why does the Corpus Luteum produce more Progesterone than Estrogen?

In the human ovarian cycle, follicular cells produce only Estrogen in high concentrations (to my knowledge). Yet after ovulation and formation of CL, which should be the remnant follicular cell mass, ...
Sriram Patnaik's user avatar
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Why does the sympathetic nervous system constrict in heart failure?

As I learn about heart failure in medical school, we are consistently taught that one of the compensatory responses to heart failure (and the accompanying reduction in cardiac output) is for the ...
to_change's user avatar
2 votes
1 answer
554 views

How could microplastics accumulate in the bodies of marine mammals?

I have read several literature reviews and studies on the effects of microplastic particles on fish and invertebrates (one example includes the review by Franzellitti et al. (2019)) and there are ...
Maddie Matei's user avatar
1 vote
1 answer
220 views

Entry of particulate pollutants into the nasal cavity

NCERT Chemistry of Grade XII (India) writes Particulate pollutants bigger than 5 microns are likely to lodge into the nasal passage, whereas particles about 10 microns enter the lungs easily. I'm ...
Ansh's user avatar
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5 votes
1 answer
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Which animal has the smallest percentage of their body mass made up of water?

It's a "well known" and interesting "fact" that the human body is made up of "mostly water". With percentages from 65% to 90% often being repeated as if they were exact ...
Harthag's user avatar
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3 votes
0 answers
39 views

Does the kidney regulate sodium balance or total body sodium

Imagine the following situation. You have a person who initially eats 10 mEq/day of salt. He then, at t=0 begins to eat 150 mEq/day of Na, and will continue to do so, because you're forcing them to, ...
to_change's user avatar
2 votes
0 answers
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What benefit do cardiomyocytes accrue by requiring calcium induced calcium release (relative to skeletal myocytes)?

According to 2 sources I've read, in contrast to skeletal myocytes, cardiac myocytes need calcium to diffuse in to result in contraction. One source says that they need large amounts of calcium to ...
Robert S's user avatar

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