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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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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Does variation in human gut length vary predictably with diet of ancestors?
Background: Numerous online searches, textbooks and other sources seem to pin the average length of the human gut from mouth to anus (oroanal) between about 5-10m in length. To pick a reputable ...
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Why some tissues like small intestine epithelium are able to be replaced so often, yet they are not one of the most common cancers?
My small intestine epithelium cells are replaced thousands times more than my prostate. Yet I'm much more likely of getting a prostate cancer than cancer on my intestine epithelium. Is there a known ...
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Why do children not have the Acid Mantle?
Post puberty humans begin to secrete a substance called Sebum which changes the neutral PH of our skin from ~7 to 4.5-5.5. This has that advantage of serving as a protective line against pathogens and ...
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Which single substance among Potassium and Phosphate has the greatest osmotic activity in the Intracellular fluid?
My physiology textbook mentions that potassium has the greatest concentration ( 155 mEq/L ) in the Intracellular fluid and that I thought would make it the most osmotically active but the answer given ...
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How long does it take to reset sense of smell?
I have noticed that when I go on vacation for several days and then come back home, there is a distinctive, relatively mild paint smell in my apartment complex. However, under normal circumstances, ...
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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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What happens to apetite hormones like ghrelin and leptin when a person in coma?
Don't coma individuals feel hungry? If so, how does the brain senses this condition (as coma is caused by neural death or damage) and switches off gene expression of ghrelin and leptin.
Is there any ...
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What is the lifespan of Skeletal Muscle Cells?
I have read that skeletal muscle cells cannot multiply and are generally not created after early development. However, I have also read that they have a "lifespan" of 10-15 years. Could this lifespan ...
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How long does it take for a new muscle fiber to be connected to motor neuron?
When new muscle fibers are formed through hypertrophy, how long does it take for motor neurons to connect to the new muscle cells in order to be able to control them?
After taking a break from ...
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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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What is the average volume of the human Psychic tear? ("emotional tear")
My goal is to find out the volume of the average human "emotional tear" (Psychic tear - sadness, happiness), specifically when crying. I found a lot of information about Basal tears (constant ...
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What's the ratio of saturated to unsaturated fatty acids in human cell membrane?
It's well established that the fluidity of a cell is largely dependent upon the ratio of saturated to unsaturated fatty acids that exist within the membrane, but, what exactly are the values for this ...
user22020
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Plant vs animal protein digestibility?
The protein scoring methodologies ( https://en.wikipedia.org/wiki/Protein_Digestibility_Corrected_Amino_Acid_Score) rate plant proteins of a lower quality than animal proteins. Now I can understand ...
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Empty room, Room full with stuffs & Auditory adaptation to reflection of sounds
Background
When a room is full with stuffs like furniture, electronic utilities, books etc. it's hard to hear reflections of sounds made by us (talking, playing an instrument, sound from falling ...
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Pee Shiver: Any reliable research about this phenomenon?
I came across 2 webpages about the science of pee shiver.
Link 1
Link 2
I wonder if there any reliable scientific research about this phenomenon. The 2 webpages I have hyperlinked attribute this to ...
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Physiological effects of electrical shocks on human body depending on the energy
When discussing safety of electricity, one usually considers a constant DC or AC current with constant amplitude over a longer time. It is easy to find tables in books or in the web which lists ...
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Changes in spongy urethra during tumescence
How does the columnar cells of spongy urethra expand during tumescence(erection of penis)?
If we assume that the urethra has the length, long enough to sustain tumescence without expansion of cells, ...
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Why are adults so suceptible to dizziness?
I have a child and she, like pretty much all the others it seems, loves spinny rides in the park. Adults often can't stand them.
In fact, I recall going from loving to hating dizziness over the space ...
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Coagulation of blood in small intestine due to trypsin
Trypsin is secreted in the small intestine to convert proteins into dipeptides i.e. to carry out digestion of proteins. However, it is also a coagulating agent which coagulates blood by hydrolysing ...
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Why is there a structural difference between the bicuspid and tricuspid valve?
There are three cusps in the tricuspid valve and only two in the bicuspid valve? Why is there such a structural difference? Does it have anything to do with that there is oxygenated blood on the left ...
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How do we sneeze?
When a stimulus triggers the sneezing pathway, known as the trigenimal nerve network, how do the droplets from a sneeze get created within the nose? What affects the size of these droplets?
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When a muscle contracts, but not all the muscle fibers are activated, what happens to the remaining muscle fibers?
I understand how motor neurons work, but I would like clarification on what exactly is going on when a muscle contracts. For the sake of simplicity, let's just use the bicep as an example. If I do a ...
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What proportion of lung compliance is attributable to alveolar surface tension?
I am reading Guyton and Hall, chapter 38, Pulmonary Ventilation. It states that the two main factors influencing lung compliance are 1) tissue elasticity 2) surface tension elastic force. An ...
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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 ...
user73773
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Has electrical activation, rather than mechanical tension been investigated as a direct trigger for hypertrophy?
Three of the most common theories for what induces hypertrophy are mechanical tension, muscle damage and metabolic fatigue.
The prevailing theory at the moment is that mechanical tension is the main ...
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Vitamin B12 deficiency Megaloblastic anemic
I have two doubts regarding Megaloblastic anemia which shakes my mind
(1) first is- I know that vitamin B12 is required for thymidine synthesis which is further required for DNA synthesis and so if ...
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Type B Nerve fibres cause exactly what kind of autonomic sensation to the preganglionic neurons?
Ganong's Review of Medical Physiology (25th ed) presents the Erlanger and Gasser classification of mammalian Nerve Fibres as such:
Type B Fibres are concerned with Preganglionic autonomic sensations, ...
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How would our vision be improved if our photoreceptors were not backwards?
I'm curious to how much better human eyesight would be if the nerves from our rods and cones were correctly placed behind the receptors?
Are there any Animal Models with correctly placed ...
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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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ATP and Muscle Contraction
I have a question regarding how molecular interactions manifest in physical actions - such as hanging from a bar. To the best of my understanding, when it comes to the contraction of muscles, ATP is ...
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What is the evolutionary advantage of getting hard nipples when being aroused? Why can they even be stimulated sexually?
I try to understand the evolutionary advantages of the body reactions of nipples and penises/vaginas. I'm confused, because I can explain the evolutionary advantage in a logical & consistent way ...
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Why do I have super vision in purely red light?
I installed some RGBW led strips in my apartment recently.. by some I mean everything is now lit by led strips and there isn't a single light bulb left.
One thing I've noticed over the last few days ...
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Why does the ova remain viable for only a day after ovulation?
The ova remains viable for approximately 24 hrs after ovulation to be fertilised by a sperm.
...chances of becoming pregnant increase dramatically if you have sex during the 5 days before ovulation ...
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Role of neuraminidase in preventing polyspermy in humans
Neuraminidase is a hydrolytic enzyme present in the acrosome of human sperm. It removes neuraminic acid (salic acid) from glycoproteins. I have read in a book that due to this reason it (the enzyme) ...
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More *total* oxygen absorbed by breathing fast or slow?
I have heard that human lungs capture/absorb/process more oxygen by breathing slower.
A) Is the above true?
B) If so, if my primary concern was absorbing the most total oxygen (not most efficient), ...
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Does the humeroradial joint move medially/laterally?
The humeroradial joint is a ball-and-socket joint that, if unrestricted, would allow for movement around all possible axes. However (as succinctly stated from Wikipedia):
the annular ligament, by ...
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Where can I find a list of medical conditions and their incidence rates?
Where can I find a list of diseases and their incidence rates? I'm giving a presentation on Long QT Syndrome, which affects 1 in 2000 people, or 50 per 100,000. I'm trying to find other, more well-...
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Sensing weather conditions through bodily reactions (e.g. dry hands, arthritic pains)
Two fairly known examples of the effect of certain weather conditions on the body are dry hands due to decreased air humidity around us (more commonly in the winter, as described here), and flaring of ...
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Portal Systems in Humans
I was reading about nephrons in my physiology book when i came across this-
The efferent arterioles and peritubular capillaries technically constitute a portal system
But according to Wikipedia, ...
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Why does rapid decompression make you lose useful conciousness so fast?
I was watching Smarter Every Day's episode on hypoxia, and it had an interesting chart that suggested that at 35kft, you have less than 10 seconds of useful consciousness. This number seemed low, and ...
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How to tell if something is an organ or apparatus?
An apparatus is defined as
Physiology. a group of structurally different organs working together in the performance of a particular function.
An organ is defined as:
Biology. a grouping of ...
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Pressure produced by blowing with mouth
I need some figures on the pressure humans are capable blowing with their mouth with zero flow. I only need very approximate figures. I'm guessing around 500mm of water? I haven't got a tube handy to ...
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Why do workouts cause your muscles to feel heavy?
I know that muscle activity causes your muscles to build up lactic acid. Is this the specific reason that your muscles begin to feel heavy? How does this relate to the healing or inflammation process ...
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How does sperm gets oxygen in the female reproductive tract?
At the time of insemination, sperm along with seminal plasma enters in female reproductive tract and the plasma contains fructose for providing the energy to sperm
If the fructose follows just EMP ...
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How do painkillers prevent shock?
I was reading about the Placebo effect and came across this little story:
The roots of the placebo problem can be traced to a lie told by an
Army nurse during World War II as Allied forces ...
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Does Lymph Clot?
According to my professor, lymph has the ability to clot because it contains plasma which has dissolved fibrinogen. He says that as long fibrinogen is present in a bodily fluid, it should be able to ...
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What happens to the gamma motor neuron during too much contraction of a muscle?
Suppose a muscle is contracting too much, so we need a reflex to stop it from contracting too much.
Contraction of a muscle causes the muscle spindle to go slack, hence the Ia axons and II-axons do ...
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What torque can the human wrist take?
Say you are holding a rod in one hand with your tumb on one side and the rest of your fingers on the other. What amount of torque could be exerted onto the rod (with the axis of rotation being around ...
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Why’s brush bordered columnar epithelium found in intestine and not brush bordered cuboidal when I’ve been explained that they have the same function?
I searched for differences between their functions which would result in their positioning but none of it satisfied the answer to my above question.
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