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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24 views

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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436 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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1answer
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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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15 views

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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1answer
30 views

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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1answer
73 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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30 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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1answer
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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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1answer
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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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Why is phagocytosis not included as a type of receptor-mediated endocytosis?

A common classification of endocytotic processes groups them into Phagocytosis, Pinocytosis, and receptor-mediated endocytosis (1) & (2). But Phagocytosis involves the use of specific receptors ...
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239 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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2answers
134 views

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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1answer
26 views

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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Getting confused by neutralizer, fixator and stabilizer muscles

I know that neutralizers may also be classified as stabilizers because it is their ability to keep joints balanced that holds motion along a specific path. A fixator muscle is a stabilizer that acts ...
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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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Specific and non-specific endocytosis

I am confused as to what endocytic processes are termed specific and non-specific. I am only sure of pinocytosis as a non-specific process but I can't successfully put phagocytosis in the right ...
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1answer
116 views

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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2answers
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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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What is the physiological function of the CoV-2 targeted ACE2-Mas receptor pathway on lung/nasal epithelial cells?

CoV-2 targets ACE2 receptor on epithelial cells, pneumocytes, as well as nasal cells which seem to be cells of the nervous system (loss of smell is a symptom of Covid). ACE2-Receptor is rather well ...
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1answer
99 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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1answer
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Why Can't Muscles Push When They Return To Their Original Length?

I understand that muscles can only contract and shorten and thus can only pull, but why can't a muscle push when it relaxes and returns to its initial length?
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How to estimate oxygen consumption of an average human during different activities?

I've tried to find some resource on the internet but had little luck. I'm looking to see if there's any data on average oxygen consumption of average to well trained humans during different activities....
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140 views

What stops myosin during muscle relaxation?

I understand that when the muscle is relaxed tropomyosin blocks myosin binding sites on actin filaments thereby preventing muscle contraction. What I am concerned with however, is whether myosin ...
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2answers
112 views

Is water movement across cell membrane purely diffusive or it always requires channels?

If we see nephrons, in the descending part of Loop of Henle (LoH), water movement is allowed but solute movement is not. On the contrary, in ascending LoH, solute movement is allowed but not water. ...
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Does The Sympathetic Nervous System Increase or Decrease Urination?

According to my book: Sympathetic nervous system stimulation, leads to the release of Norepinephrine(Noradrenaline), priming the body for the "Fight or Flight" response. It is also stated ...
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Why does dryness irritate mucosal surfaces, and what exactly is this “irritation”?

The mucosal surfaces of the body function to moisten the epithelial linings and keep them from becoming dry. Why is this important? As an example, the respiratory tract moistens and warms the air that ...
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1answer
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Question on thick filaments

In this photo, I know that the arrows pointing towards the M-line of sarcomere on actin filaments are due to the power strokes of myosin heads. However, what I don't understand are the arrows on the ...
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55 views

Understanding muscle tone

I am relatively new to Physiology, and I've just learnt about muscle tone. I however find it difficult to understand the electrical changes that initiate (and/or accompany) muscle tone in smooth ...
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Summation on muscles

I am learning myology and encountered 2 problems in tetanus and summation: Unfused tetanus is just a continual summation of twitches if I am not mistaken. However, is it a MUST for summation / ...
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what powers power strokes

I am wondering what really powers the myosin head to undergo the power stroke to push the actin filaments towards the M-line. I have 2 thoughts: when ATP in the myosin head gets hydrolyzed, the ...
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1answer
32 views

What inhibits linkage between actin and myosin filaments

What is the mechanism behind the inhibition for cross-bridge linkage between actin and myosin filaments in the binding-tilting cycle? There are 2 possible ways that are in my mind: a. Tn-I (tropnin-I)...
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What is the difference between muscle contracture and muscle rigor

My text says muscle contracture is a state of sustained muscle contraction due to depletion of energy. And muscle rigor is the stiffening of muscles when they're depleted of energy. So, what exactly ...
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1answer
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Does electrotonic spread/conduction occur in saltatory conduction?

Even as textbooks, and almost all web pages I've seen so far, explain electrotonic spread/conduction as the passive current flow along an axon, they do so with continuous conduction only. Apart from ...
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Do birds have pharynx like mammals? [closed]

I saw this in Wikipedia: Birds do have a larynx, but unlike in mammals, it does not vocalize. And this pdf in Google. It claims that birds do have a pharnyx. Do birds have a structure called pharnyx?...
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Why does increasing concentration of extracellular sodium have no effect on electrical gradient of potassium? [duplicate]

I learnt that the permeability of an ion across the membrane contributes to the membrane potential as much as(or even more than) its concentration and electrical gradients. And so far I've made peace ...

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