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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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, ...
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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 ...
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11 votes
1 answer
521 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 ...
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1 vote
1 answer
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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 ...
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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 ...
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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, ...
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2 votes
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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 ...
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What are the possible causes of Lactase persistence?

Lactase enzyme which is responsible for the digestion lactose (a disaccharide milk sugar) normally its production decreases when a young mammal is weaned but mostly Humens continue to produce this ...
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2 votes
2 answers
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Why does damage to myelin sheath in multiple sclerosis lead to a decrease in information reaching the brain from sensory receptors?

In multiple sclerosis(MS), myelin sheath is attacked and damaged. When this happens, there is a decrease in the amount of information reaching the brain from sensory receptors. How and why does a ...
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15 votes
2 answers
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Can mosquitoes be attracted by our voice?

In the dark, mosquitoes use CO2 to find blood host like us. However, 1) they are known to have an excellent auditory organs (ref1, ref2) ) and 2) sound can be heard from any direction, contrary to ...
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Where does nitrogen go or come from as its partial pressure in different parts of the lungs decreases or increases?

Here's a table from Guyton and Hall Textbook of Medical Physiology showing the partial pressures of gases in different types of air: We can see that as the partial pressures of some gases decrease or ...
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In renal tubules, do intraluminal, intracellular, and interstitial CO2 compete to form H+ and HCO3-?

From Guyton and Hall Textbook of Medical Physiology, Chapter 31: Bicarbonate ions do not readily permeate the luminal membranes of the renal tubular cells; therefore, HCO3− that is filtered by the ...
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Does an "empty stomach" have acid in it?

I know that the pH of the acid in an empty stomach is higher than a stomach with food. I was trying to understand how water passes through stomach to intestines with the absence of food. But this ...
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1 vote
1 answer
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Why do blobfish become bloated when they are brought to the surface?

There are several things that can happen to deep sea creatures that are brought up to the surface, but none of them explain why the blobfish becomes deformed. Blobfish don't have swim bladders, so ...
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Effects of high extracellular fluid calcium ion concentration - what's the reason behind it?

The Guyton and Hall Textbook of Medical Physiology, p. 76, says: For example, a high extracellular fluid calcium ion concentration decreases membrane permeability to sodium ions and simultaneously ...
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Why does distention of the veins not decrease their resistance in the first case but decrease it in the second?

Here are two quotes from Guyton and Hall Textbook of Medical Physiology, Chapter 20 (emphasis mine): Why is venous resistance so important in determining the resistance to venous return? The answer ...
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3 votes
1 answer
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Why does vasodilation increase blood flow in the capillaries, but decrease it in the chest during inspiration?

From Guyton and Hall Textbook of Medical Physiology: Every time a person inspires, the pressure in the thoracic cavity becomes more negative than usual, causing the blood vessels in the chest to ...
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5 votes
2 answers
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Why is Heart Rate Recovery after exercise reasonably well described by a mono-exponential decay?

I have been measuring my heart rate recovery after exercise and I see that it can be fit reasonably well using a single exponential: $HeartRate(t) = HR_{max} \times e^{-t/\tau} + HR_{resting}$ This ...
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2 votes
1 answer
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After digesting food, where does the energy go before being stored by the body?

I'm trying to piece together a simplified model on how the energy flows in the human body. From what I understand: We store enough ATP for around 2 seconds of maximum exertion We store enough ...
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1 answer
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How much percentage of substance does liver take in one pass?

The portal vein system is to feed the absorbed nutrition and toxin (defined as "substance" here) to liver first for it to take them up as fast as possible, before they reach other organs ...
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Medical Physiology

I've come across the topic of the influence of inhaled ammonia (caustic ammonia) on breathing rate and some cardiovascular changes. All of this stuff is thought to be mediated through the fifth ...
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Why do people make "aaagh" noises when they make an effort (e.g. trying to hit a ball hard)?

I'm referring to, for instance, grunting in tennis. It refers to how many tennis players make loud "aaagh" noises when hitting a ball. In daily life, people often also do this when trying to ...
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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 ...
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1 vote
1 answer
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Why does the time to reach equilibrium across a membrane decrease with concentration?

We're learning about flux and Fick's law and there's one point I'm having trouble understanding. Assuming we have a higher concentration of a species on one side of a membrane, I understand that ...
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0 votes
1 answer
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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 as the cell is replicating according to ...
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1 vote
1 answer
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What are the roles of ATP and ADP in muscle contraction?

I've always known that the hydrolysis of ATP generates ADP, P, and energy, so I'd assume that if energy is necessary in a given process, ATP hydrolysis should occur (or another exothermic process). ...
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If blood vessels mostly aren't supplied by parasympathetic nerves, how effects through M3-ACh receptors are mediated?

Blood vessels throughout the body mostly aren't supplied by any parasympathetic fibres. But the effects of ACh through M3-ACh receptors would infact release NO (which acts on VSM and causes ...
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-1 votes
1 answer
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Which processes in the human body depend on natural selection among cells?

Are there processes in the human body which occur via natural selection among cells? Could anyone provide examples? E.g. when tissues are conditioned to be stronger, such as a rock climber's skin ...
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5 votes
2 answers
464 views

Pathogens vs Microbes and the Immune System

I hope my question isn't too basic or silly. I am currently learning about infectious diseases in Year 11 Biology right now, and I'm stuck at the concept of pathogens and micro-organisms. Whenever I ...
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6 votes
1 answer
186 views

Is there a function for urea in sweat?

In ureotelic organisms, ammonia is converted to urea for excretion primarily in the liver and, to a lesser extent, in the kidneys. However, sweat also contains trace amounts of urea. Is this small ...
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How do smooth muscles function without myoglobin?

Myoglobin serves important function of Oxygen storage in Skeletal and Cardiac muscles. However, It is absent in smooth muscles. Why is it absent in smooth muscles? Why smooth muscles don't need ...
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1 vote
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What is the term for the physical and behavioral changes that occur in an adult species due to the change in their hierarchy?

For example, when a chicken becomes a rooster its crest becomes larger and their feathers become more colorful. Dominant male lions get larger and darker manes. Also, can these changes also occur ...
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3 votes
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Why does (insulin induced) hypoglycemia stimulate ADH secretion?

Intuitively, I understand that ADH (Anti Diuretic Hormone) is responsible for maintaining osmolarity, and increased serum osmolarity is a stimulatory factor for its release-- ADH increases water ...
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6 votes
1 answer
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By what mechanism do cephalopods regrow limbs?

As far as I can tell, there are two types of limb regeneration: epimorphosis and morphallaxis. Epimorphosis is used by animals such as amphibians and various phyla of worms, while morphallaxis is used ...
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5 votes
1 answer
113 views

How much light can pass through the human eyelid?

My sister tells me that at night when the lights in the room are off that she can see the ambient outdoor light from neighboring buildigns and streetlights through her eyelids (i.e., when her eyes are ...
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1 vote
1 answer
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GHK Equation and Action potential

Can GHK equation be used to predict the membrane potential even if the cell is not at resting state? To say it again, can we use GHK equation at every moment during Action potential? I'm confused ...
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1 vote
1 answer
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Can oxytocin travel from one cell to another via gap junctions?

Oxytocin is a 9-residue secreted peptide. As a hormone, can it travel through gap junctions, assuming that it is stored in pre-synaptic neuronal vesicles?
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3 votes
0 answers
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Hodgkin-Huxley Model and Propagation of Action Potential

I'm studying Hodgkin-Huxley model of action potential, and I have some confusion. In the well-stated HH model, we have time constants for each ion currents, described as the reciprocal of the sum of ...
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Maximum Allometry of aquatic mammals omitting Kleiber's Law

As far as I understand, blue whales cannot get any physically larger due to the extremely demanding caloric intake it has on consuming large quantities of krill, not due to any other physiological ...
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1 vote
0 answers
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What is the water content of avian blood?

I'm doing a work about heavy metal contamination in seabirds. I have found that the toxic threshold for Cu in blood is 1,15 μg/g wet weight. That number refers to an average between some seabirds. I ...
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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 ...
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0 votes
1 answer
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Do factors other than concentration gradient and membrane permeability affect the diffusion potential?

If, hypothetically, the concentration gradients and the permeability of 2 different ions (Na+ and K+ for example) in 2 separate solutions are the same, will the diffusion potentials be different? I'm ...
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1 answer
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How do birds eliminate oxygen free radicals [closed]

Birds breathe in a lot. Do they produce a lot more of oxygen free radicals than mammals? And how do they cope with oxydative stress? Thanks!
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-3 votes
1 answer
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If you only ate fruits, vegetables or smoothies would you be able to skip drinking water?

If you only ate fruits, vegetables or smoothies would you be able to skip drinking water? I do not see some animals (like squirrels) drinking water daily (doesn't mean they don't have a water source) ...
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2 votes
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Is it incorrect to assume alveoli as spherical and distinct, especially when analysing lung inflation/deflation?

I have recently read the paper "Laplace’s Law and the Alveolus: A Misconception of Anatomy and a Misapplication of Physics". To summarise it, here is a section from its abstract: The ...
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Is my understanding of the Bergmann's rule correct? (mass is secondary)

According to Wikipedia, Bergmann's rule applies because animals living in colder areas have greater surface-area-to-volume ratio. If I understand that correctly, the advantage of the bulkier bodies ...
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4 votes
1 answer
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What is Lysoferrin?

I was going though my Guyton and Hall Medical Physiology when I came across the name of an antibacterial lysosomal enzyme - Lysoferrin. It said that Lysoferrin "binds to iron and other metals ...
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1 vote
2 answers
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Garden Hose Analogy for Blood Vessel Resistance

I've been trying to reconcile the resistance component of Poisseuille's law with a mental analogy of a garden hose; specifically, I had assumed that the effects of reducing the radius of a blood ...
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How can the pressure during contraction vary between the left and right ventricles?

After reading this passage from my physiology textbook (Vanders Physiology p. 384), I'm confused about how exactly the right and left ventricle can create markedly different pressures as they pump ...
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Is there any correlation between animal diet and blood pH?

The alkaline diet claim that as we humans have a slightly basic pH we shouldn't eat acidic food like meat (I think they claim that meat ashes are acid). I was wondering that if carnivores animals ...
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