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 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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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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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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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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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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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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61 views

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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Will renal blood flow decrease in response to dehydration?

If dehydrated, does the correction of ECF osmolarity happen slowly enough for ECF (and therefore plasma) volume to be temporarily depleted and therefore reduce renal blood flow? If dehydration is ...
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Why does increasing the space constant increase conduction velocity in myelinated neurons if nodes of Ranvier are constantly spaced?

If depolarisation at one node of Ranvier triggers, by passive conduction, an action potential at the next node of Ranvier, why does increasing the space constant increase conduction velocity? Surely ...
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Can severe vasoconstriction increase systolic blood pressure?

I know that, vasoconstriction results in increased total peripheral resistance which is responsible for the rise in diastolic blood pressure. Also, cardiac output is responsible for the systolic blood ...
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58 views

How does noradrenaline result in rise of systolic blood pressure even when the cardiac output is decreasing?

Systolic blood pressure[SBP] depends on the cardiac output. When Nor adrenaline is given there is vasoconstriction due to alpha-1 action on blood vessel, vasoconstriction results in increased total ...
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is ventricular depolarisation same as depolarisation during nerve impulse conduction? [closed]

Does the change in membrane charge accumulation occur in a similar way in heart and nerves cells?
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Na+ / K+ ATPase: How does it restore resting membrane potential? [duplicate]

Could not find any sources talking about this (in a clear manner). If the Na+ / K+ ATPase pumps 3 Na+ out for every 2 K+ it pumps in, thus making the cell more negative, why is the Na+ / K+ ATPase ...
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237 views

At small axon diameters (<1 µm), why does myelination not increase neuronal conduction velocity?

As per the diagram below (and other graphs available online), why do unmyelinated fibres have a higher conduction velocity than myelinated fibres when the axon diameter is less than around 1 µm?
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Asexual Reproduction Of sponges through endogenous or exogenous budding?

I was studying asexual reproduction in sponges and came across two website Wikipedia of Gemmule and there is a line.... Only Endogenous Types of Buds develop into New Sponges. Then as I was reading ...
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Taking cold shower / drinking cold water after / during training

(I am a new-comer in biology SE so sorry if violated any rules) Effect of cold showers after intense training I have read the answer to this question, but it seems there are discussions on the ...
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Why largest cats so much larger than canids?

It is striking to me that there is no dog-like creature larger than a wolf while there are at least two species, tigers and lions, many (at least twice and probably 3 or 4) times the size of the ...
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What is the pH of cytosol? And plastids?

My teacher ask this question, and I answered 7 to 7.4, but she said it's wrong. I read a lot and found the same answer (wikipedia) I'm here asking for confirmation of this and the pH inside & ...
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122 views

Humans best at long distance running: purely physiological or is it a function also of ability to pace?

I have read that although certainly other land animals are much faster over short distances, a human can run down any other animal over time, so that if a human is hunting like a gazelle, etc. ...
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What happens to intrinsic factor exactly at the terminal ileum, where B12 is absorbed?

IF is very important for IF-dependent B12 absorption in the terminal ileum, the mechanism by which most of dietary B12 is absorbed. The B12-IF complex bind to IF receptors on enterocytes, but does the ...
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What causes paresthesia from compression?

Compression of a nerve causes loss of afferent and efferent information in it. What is the physiological basis of this?
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51 views

What are some good books on oncology?

I'm looking for some book suggestions on oncology, preferably I want them to be fairly recent. I am not worried if they are fairly technical, as long as they have good accurate content and layout.
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What is blood pH for different animals?

So we all know that humans average blood pH is 7.4. But is it the same for the animals? I need examples of animals with the same blood pH as humans and the ones with different blood pH. I guess dogs ...
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202 views

Is breathing a reflex action or is it an intrinsic process?

The process of breathing is controlled by respiratory centers in the brain stem. Do these centers have an innate activity, i.e., just send out signals to breathing muscles intrinsically, and have the ...
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Does a tubular sodium reabsorption cause a stimulation of β2-adrenergic receptors?

I read the study "The Role of Aldosterone in Obesity-Related Hypertension" and there is one thing I didn't understand. They write: "According to norepinephrine-induced tubular sodium reabsorption, ...
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Electrical transmission vs Chemical transmission

"The advantage of electrical transmission, apart from speed, is it can favour synchrony in firing. For example, in the brain stem a nucleus called the inferior olive can generate oscillations due to ...
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What does sympathetic and parasympathetic 'tone' mean?

My professor's lecture notes say that " The basal rate of firing is called “sympathetic tone” and 'parasympathetic tone" , but a table I found on the internet says that the parasympthetic system has ...
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Is there any case in which excitability increases with lowering the RMP?

My professor says , at a more negative RMP, less sodium ion channels are inactivated, so if you take 2 of the exact same neuron with the same threshold potentials, and try to excite them starting from ...
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Im struggling to see how these are presynaptic terminals/knobs and not post synaptic

How are these presynaptic terminals ? The action potential is generated at the axon hillock and moves down the axon (in this case to the right) , then at the end of the axon should be axon terminals ...
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116 views

Why is the ratio between action potential and threshold value called the 'safety factor'?

"All­or­Nothing Principle. Once an action potential has been elicited at any point on the membrane of a normal fiber, the depolarization process travels over the entire membrane if conditions are ...
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What was the evolutionary benefit of enclosing hemoglobin in cells?

The ancestral solution to oxygen transport is with hemoglobin (or, similar proteins) dissolved in blood (or, "hemolymph", but, basically, dissolved in water. ) What was the advantage of enclosing the ...
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350 views

Osmosis and hydrostatic pressure

I'm confused about the role of hydrostatic pressure compared to osmotic pressure. Q1:If I have a U-tube with a membrane permeable only to water molecules and equal volumes of water on either side ...
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Are ligand gated channels saturable?

A major difference between simple diffusion and facilitated diffusion is that facilitated diffusion has a maximum transport and velocity; the rate of diffusion is limited, whereas in simple diffusion, ...
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235 views

Nernst equation and equilibrium potential

Solutions A and B are separated by a membrane that is permeable to Ca2+ and impermeable to Cl−. Solution A contains 10 mM CaCl2 , and solution B contains 1 mM CaCl2. Assuming that 2.3 RT/F = 60 mV, ...
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Do endocrine cells always lie adjacent to capillaries?

The circulatory system transports plasma contents to the body via the interstitial circulatory system, reabsorbed with the lymphatic system. Cell metabolism "waste products" are transported into the ...
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Are there any animals that are unable to hear the human voice?

Humans and animals have different hearing ranges. The frequency range of a human, for example, is stated with 20 Hz to 20 kHz, whereas the fundamental voice frequency is stated with 125 Hz for men, ...
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Why do patients with type 2 diabetes not show the body wasting seen in type 1 diabetics?

Type 1 diabetes results from the destruction of the cells in the pancreas that produce insulin, while type 2 diabetes is characterized by so-called "insulin resistance", presumably a reduced ...
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How does chest wall compliance affect functional residual capacity (FRC)?

The functional residual capacity is made up of expiratory reserve volume (ERV) plus the residual volume (RV) - i.e. the volume of air remaining in the lungs after passive expiration. Compliance of ...
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Why would it be beneficial for cortisol and corticosterone to exhibit pronounced anti-inflammatory activity?

These questions are always a little silly (as we will never truly know), but it always struck me as odd that corticosterone and cortisol exhibit pronounced anti-inflammatory activity. Because these ...
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Why is arterial pO2 normal in carbon monoxide poisoning?

Arterial blood gas measurements often show that pO2 is 'normal' even though haemoglobin is bound to carbon monoxide with high affinity. Is this because there is still oxygen bound to some subunits of ...
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1answer
26 views

Is mucus significantly affected by the presence of ions?

In mucus, there is besides water and the mucins (Proteins for mucus), there are Ions like $Ca^{2+},Na^{+}$, etc. I have read that These Ions can Control the mucus swelling, i.e. the volume that the ...
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Why does higher venous volume increase atrial pressure?

If the cardiac output stays the same (hypothetically, although obviously it doesn't stay the same), then why does higher venous volume increase right atrial pressure? Shouldn't the flow rate be ...
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What is the human energy consumption by organ?

The human brain uses about 25% of the human body's metabolic energy. How are the other 75% spent, in terms of portioning to its various systems? I thought this could be answered by a simple search, ...

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