Questions tagged [human-physiology]

For questions on the biochemical, physical, and mechanical functioning of humans in good health including their organs and cells.

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31 views

Concept of mean systemic filling pressure

Mean circulatory filling pressure (MCFP) in humans was defined by Guyton as "the pressure that would be measured at all points in the entiere circulatory system if the heart were stopped suddenly ...
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50 views

What are biological needs of a person? [closed]

the biological needs of a person may include hospitals, Blockquote consultation with doctors, medicines, and hospital operation or surgery. ...
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45 views

What is “KK1 enzyme”?

In the book "The Kaizen Way" by Robert Maurer, I've read the following: When we’re sitting, our muscles go into a form of hibernation, causing our bodies to shut down the enzyme (called KK1)...
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63 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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52 views

What is the function of human Trypsin Inhibitor if trypsin is secreted in the inactive form of Trypsinogen? [closed]

I was reading about pancreatic digestive enzymes in a Textbook of Medical Physiology and I came across Trypsin Inhibitor. The text stated that: It is important that the proteolytic enzymes of the ...
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1answer
77 views

Why does exhaled air still contain oxygen?

If the partial pressure of oxygen in the atmosphere is 159 mmHg and that inside human alveoli is 104 mmHg, and if these values are fixed or don't change very much, then why does exhaled air have ...
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95 views

Why does this oxygen duration chart have increased times above 30,000 FT MSL?

This oxygen duration chart from an airplane shows the amount of time a pilot can be on oxygen at a specified altitude (in 1000s of feet). For example, the chart shows two pilots able to cruise at a ...
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12 views

Using serotonin for relief from allergies

When someone suffers from an allergy, due some allergens they are given drugs like anti-histamine, adrenaline or serotonin. How does serotonin affects the body to give a relieve from the action of ...
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23 views

How does mannitol decrease intracranial pressure?

What is the mechanism by which mannitol is able to reduce intracranial pressure? Also why aren't other substances used for this purpose such as say sorbitol (an epimer) or in fact any other ...
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How do the biophysics of how cerebrospinal fluid mechanically protects the brain work?

The two mechanisms I've seen mentioned are the cerebrospinal fluid (CSF) acting as a hydraulic cushion or shock absorber, and how CSF creates a micro-gravity environment through buoyancy. I have very ...
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17 views

Why does glomerular filtration result in a filtrate with the same osmolality as plasma?

Unlike the plasma, the ultrafiltrate has no proteins which are prevented from filtering out. Shouldn't the loss of these proteins result in a loss of oncotic pressure and thus a different overall ...
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Why do beta-1 and beta-2 adrenergic receptors result in two completely different effects (though both use Gs pathway)?

$\beta_2$ adrenergic Receptors are $G_s$-coupled 7-TM proteins. Considering that $G_s$ , by activation increases $[\text{cAMP}]_\text{cytosol}$ which inhibits MLCK of smooth muscles (and causes ...
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Why severely increased Ligand (eg Hormones) concentration downregulates the Receptor?

As an example continuous high blood level of GnRH in humans causes a suppression of LH and FSH. This is due to the fact that increased GnRH downregulates GnRH-Receptors . My question is how this is ...
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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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17 views

Topography of motor deficit and spasticity in UMNS

As a medical student, I have been told that upper motor neurone syndrome is a cause of motor deficit and spasticity. The motor deficit is said to be affecting predominantly the extensor apparatus at ...
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21 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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1answer
56 views

Partial pressures of different gas in human blood and how they are calculated?

In Respiratory Physiology, we use the $P_x{O_2}$ and $P_x{CO_2}$ in blood at different regions of the peripheral circulation. From my Chemistry knowledge I know that $P_x$ of a gas in a solution is ...
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37 views

Are intestinal and pancreatic lipases different?

For explaining the action pancreatic lipase, my book wrote this equation:- $$fat\space particles + lipase\rightarrow fatty\space acid + glycerol + lipase$$ But for intestinal lipase, my book has a ...
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25 views

Under which conditions is human energy consumption minimized?

Including but not limited to: body state consumed food composition state of the digestive tract diseases wounds sleep coma, etc.; death excluded environment state temperature light pressure, etc. ...
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42 views

Do pinhole glasses help reduce eye strain?

I've noticed that I can read about 10x longer at screens and books without my eyes tiring using the "pinhole trick" - where you curl your fingers and look through the hole (great explanation here ...
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53 views

Why do arteries have a small lumen? [closed]

My biology textbook says that arteries have a small lumen relative to the thickness of their walls. I understand why they need thick walls, to withstand high pressure and stretch etc. But when ...
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25 views

Why don't we dribble tears through our nose?

Basal tears are tears produced by the lacrimal gland and they lubricate the eye. They are then funneled into the lacrimal sac and then from there into the nose eventually. If this is the case, why ...
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29 views

Why does it take so long to bleed after accidentally cutting yourself?

Sorry if this is not a good site to ask this question, but I recently accidentally cut myself while chopping onions (very minor, no serious harm done), and noticed that it took quite a while before ...
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Which results in greater energy expenditure: consecutive actions, or non-consecutive actions?

Is there a difference in energy expenditure when performing the same set of movements consecutively vs non-consecutively? Example: You jump in-place 1 time, stand motionless for 1 minute, and then ...
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63 views

By what physiological mechanism do we not feel microbes (bacteria, etc.) living on our skin?

Background I know our bodies have a handful of ways to threshold our awareness of sensory stimuli: Neural density Sensory acuity I assume really tiny stimuli could fit between receptors e.g., ...
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Why and how do red bone marrow concentrations in humans change during traditional aging?

I have found several pictures that suggest this is the case. As for peer reviewed papers I've found plenty of papers hypothesizing and testing as to the why of changes in populations of HSCs, a few ...
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48 views

Why doesn't copper affect human skin?

It's been known for a long time that copper has antimicrobial properties, but if it is so potent, why does it seem to have no effect on human skin or really any large animal?
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Origins of the body mechanics theory

In physical therapy and occasionally in sports coaching, there's often a precise description of the mechanics of what happens during the movement (which muscles are engaged, which joint moves where ...
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20 views

How do precordial leads measure electrical changes in the heart?

In precordial leads the electrodes from limbs are connected to a common point via resistors. What is the potential at the common point?
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25 views

What percent of mucle growth is possible without steroids consumption?

I am interested to know, if someone does bodybuilding exercises with good rest, enough protein, high presure workout, etc, but without consuming any steroids, how much of muscle gorwth is possible for ...
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134 views

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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20 views

What's the function of vitelline circulation in human embryo?

Why do we need a vitelline circulation if we already develop a placenta to gather all the nutrients we need? Is it an evolutionary remain?
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34 views

How much blood do we have when the heart first starts to beat?

How much blood do we have when the heart beats for the first time? It should be between the third and fourth week of embryonic life.
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Reflex muscular activity in three months old fetus

At the end of the third month, reflex activity can be evoked in aborted fetuses, indicating muscular activity This quote is from Langman's Medical Embriology. Have I misunderstood it or it is ...
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206 views

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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59 views

What happens when a human ingests a large meal, and after a short time follows it up with a large amount of indigestible carbs?

A human eats a large meal and indigestible carbs (IC) with such a timing that the IC arrive to the small intestine when it is already full and busy breaking down and absorbing the meal. What would ...
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39 views

What is the relevance of the constant in the clearance equation?

I have seen the equation for drug half lives described variously as (0.7xVd)/Cl, (0.693xVd)/Cl, and (ln2xVd)/Cl. What is the origin of this numerical constant in the numerator? What does it signify?
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28 views

Physiology of hyperpolarization

In my textbook, it is stated that after the closure of potassium voltage-gated channels and during hyperpolarization, potassium leakage channels allow potassium influx passively and this returns the ...
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1answer
58 views

Was there a time in Earth's history when some animal life existed on land but humans could not have breathed?

I understand that higher oxygen content allowed insects and arachnids to grow much larger than today and I wonder if this additional oxygen would have been toxic or unhealthy for modern humans?
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70 views

Is there a nomenclature for human physiology?

Back when I studied botany in high school, the teacher taught us the nomenclature for botanical terms. I think there should be something similar for human physiology. Understanding how the name was ...
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108 views

Why is glomerular filtration called a non selective process?

According to Biology NCERT Class 11, Page 299, "Filtration is a non-selective process performed by the glomerulus using the glomerular capillary blood pressure." But the glomerulus filters out blood ...
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60 views

How does energy conversion happen (chemical to mechanical?) in moving body muscles?

From my understanding, the brain sends electrical pulses through neurons to different part of the body to initiate a movement. My question is, how is the movement realized? For example, in a train, ...
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14 views

Would DMSO Be An Effective Solvent For Creating A Transdermal Absorption of NMN + Pterostilbene + TMG In Humans?

I've read conflicting information on this. If not DMSO, is there a better solvent to use?
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How does the descending branch of the loop of Henle equilibrate concentration?

I'm learning physiology and I have a hard time figuring out how the cortico-papillary gradient is created. Most explanations go as follow: 1) Sodium is pumped out the ascending branch into the ...
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56 views

Why are human wastes yellow?

Except for the feces, which is more brownish, all the human wastes (urine, earwax, snivel, phlegm, and rheum) are usually yellowish. Why is that? I heard that urine is yellow due to bilirubin(?). What ...
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296 views

How much does capillary action contribute to blood flow to the human brain?

The BBC News Universal Wonders short video Why water is one of the weirdest things in the universe says after 01:50: Water molecules can float upwards against the ...
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77 views

Jungle blindness?

Can people who live in green scenic areas like a jungle be more exposed to green light causing them to not be able to perceive green light as well as someone who may live in a desert void of color? ...
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55 views

Sexual Reproduction in Humans

Is the human egg cell (ova) considered motile? We know that is is not actively motile but it is transferred via the fallopian tube to the uterus. Does that make it motile?
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Partial muscle fibre contraction

I'm being taught that: a muscle fibre spans the entire length of the muscle, from the originating tendon to the inserting tendon. The question is, can a muscle fibre contract only partially? Say, if ...
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30 views

What adaptations does the human body have to handle frequent and sustained changes in orientation?

Most animals are horizontal with the ground. When they lie down, they get closer to the ground, but their orientation does not change. Humans, on the other hand, stand up straight and tall, ...

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