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 LV transmural pressure contribute to afterload?

I've always understood how and why the aortic pressure contributes to afterload on the LV (higher aortic pressure means a greater pressure that the LV must overcome to eject blood; makes sense) ...
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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 ...
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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?
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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 ...
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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?
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What negative effects does heat therapy have on a recently strained muscle?

I've read on the Internet that it is a bad idea to apply heat to a recently strained muscle, and I'd like to understand why -- more precisely, I'd like to understand how the application of heat ...
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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 ...
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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 ...
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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 ...
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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 ...
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Why do rock monitors have such large snouts?

I'm looking into the anatomy of different types of African monitors. I came across the rock monitor, one of the largest lizards in Africa. One of the defining characteristics of this species is it's ...
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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 ...
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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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Glomerular capillary blood pressure is not very location dependent, why?

Question about kidneys. Let Pc; glomerular capillary hydrostatic pressure Pbc; Bowman's sac hydrostatic pressure πc; glomerular capillary colloid osmotic pressure πbc; Bowman's sac colloid osmotic ...
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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-...
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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 ...
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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, ...
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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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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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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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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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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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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 excellent auditory organs (ref1, ref2) and 2) sound can be heard from any directions, contrary to odors ...
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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