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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Are all skeletal tissues (such as exoskeleton) connective tissues?

I can't actually find a general answer for this. The search results only say that human skeletal tissues are connective. There is no result about whether clam shells, or ant exoskeletons, are made of ...
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How does the blood move if its velocity at the vessel wall is zero?

Laminar flow is the normal condition for blood flow throughout most of the circulatory system. It is characterized by concentric layers of blood moving in parallel down the length of a blood vessel. ...
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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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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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cAMP actions on body [closed]

I know that several processes are mediated by cAMP. I searched for a chart or handbook containing all processes increased or decreased by cAMP. I have a good collection about such topics but the ...
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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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530 views

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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86 views

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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67 views

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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123 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 as the cell is replicating according to ...
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52 views

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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121 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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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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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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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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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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59 views

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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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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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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127 views

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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Blood cell lineages

Blood cells are often spoken of as arising from three lineages -- erythroid, myeloid, and lymphoid lineages that will respectively produce the red cells; the platelets, granulocytes, and monocytes; ...
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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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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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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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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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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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338 views

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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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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Why do people's hands get cold for the first half an hour and then suddenly they are warm when they are doing exercise outdoors in winter? [closed]

When people do exercise outdoors in winter at temperatures less than zero degree celsius, their hands are quite cold and hurt for about half an hour. Then, there is a sudden rush of blood into the ...
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Why doesn't the concentration of one ion affect the concentration gradient of another ion across a plasma membrane?

In the initial stages, some ion channels across the plasma membrane open to allow for ions to flow down their concentration gradient into or out of the cell. I understand that each ion's overall ...
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Quantitative Physiology Textbooks Recommendations?

I am currently completing a 2nd year (UK) Mamamilian Physiology Module and a Neuroscience Module. However, my degree is also 40% Maths and Statistics. So in order to learn the content better, I am ...
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Do the posterior legs of mosquito plays the role of antenna?

I have had this question for years and this stems from the observation that when I bring my hand close to a mosquito lying on some surface (e.g : wall) I see its posterior legs - which are in a ...
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Why is urobilinogen reabsorbed from the gut just to be excreted via the kidneys?

The Wikipedia article on Urobilin states: Bilirubin is... excreted as bile, which is further degraded by microbes present in the large intestine to urobilinogen... Some is reabsorbed into the ...
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How does gas equilibration occur in the alveolus, numerically?

I am attempting to model gas exchange across the alveolar membrane. My main question is there a direct exchange of O2 molecules for CO2 molecules? If so, then my model predicts (assuming alveolar ...
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111 views

Why is the current flow shown to be flowing from the negative area towards the positive area?

When I was studying the ECG chapter in the book "Guyton and Hall Textbook of Medical Physiology", I noticed something odd in one of the pictures: As you can see the current is shown to be ...

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