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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0answers
9 views

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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36 views

Why is it harder to pee after sitting in a car for many hours?

During car rides as a passenger I can't pee as easily as when I'm home. Why?
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1answer
30k views

How can heart disease cause excessive sweating?

According to google: What can cause sudden sweating? Excessive Sweating. A person with excessive sweating has a condition called hyperhidrosis. ... In adults, the most common cause of ...
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2answers
11k views

What is the maximum altitude where humans can survive?

What is the highest altitude that a human can survive without being pressurized? Let's assume that oxygen and heat/insulation are not the limiting factors? Why I asked.
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6 views

Using EMG to measure increases in strength

I have a DIY EMG kit and I know it can be used to measure muscle activation. I am wondering, is there a relationship between muscle strength and the value obtained from the EMG sensors measuring on ...
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0answers
9 views

Are doTERRA essential oils supposed to be swallowed? I don't, but dad does [closed]

He believes that because their oils are expelled mechanically instead of chemically, they're safe to swallow. I tell him that any essential oil from any company is not meant to be swallowed because it'...
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1answer
39 views

RE: Fasting gastric pH vs Normal gastric pH

If fasting gastric pH values are more acidic then why is it recommended to eat no more than three hours before bed time to prevent reflux. It seems at some point during sleep the stomach would become ...
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24 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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17 views

Biochemistry of pleasure of/desire for physical exercise in mammalians and humans?

Are there some known biochemical mechanisms, that induces desire for/pleasure of physical exercise in mammalians and humans? I have heard, that horses can not live without physical exercise and they ...
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36 views

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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17 views

Why people feel more sleepy while doing something that's not interesting even when they are not actually tired? [migrated]

We often see people and students yawning while reading a boring course book. But, when told about something interesting, their sleepiness vanishes. Why and how does this happen? What are the exact ...
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20 views

For how long can the heart be in asystole and then restart itself?

The medication Adenosine is used for the treatment of some abnormal heart rhythms. However, according to Wikipedia, it can cause asystole for a few seconds: Because of the effects of adenosine on ...
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18 views

Do tendons thickened due to a tendon injury/pathology have the same strength as “normal” tendons?

I read in this 2015 study {1}: This study is the first to show that pathological tendons have sufficient levels of aligned fibrillar structure. Pathological tendons may compensate for areas of ...
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32 views

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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1answer
39 views

Passing out from drowning [closed]

How long does it take to pass out from oxygen deprivation? The person is panicked and screaming so they accidentally breathe water into the lungs. So how long would it take for them to pass out? After ...
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1answer
69 views

Sleeping Pill Overdose

How does an overdose of sleeping pills kill? What are the body's reactions to an overdose? In an article published in ScienceDaily, I read that "Sleeping pills owe half their benefit to the placebo ...
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1answer
309 views

Immune System - B-cell receptors

How do the B-cells, which are a part of our body, develop antibodies against antigens of the outside world (outside of our body), which they don't even know about? Is it just a random match?
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1answer
93 views

When does the brain stem appear in humans?

This article states: Once the neural tube closes, at around week 6 or week 7 of pregnancy, it curves and bulges into three sections, commonly known as the forebrain, midbrain and hindbrain. ...
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1answer
79 views

Coronary circulation

It is said that the coronary artery that gives the posterior descending artery(PDA) determines if the heart is right dominant(most cases) or left dominant. Is there any reason to this? Why PDA?
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81 views

What is the significance of different types of papillae present on tongue?

Fungiform, Circumvallate, Filiform, Foliate Papillae are present on the surface of the tongue. They have a role in increasing surface area for taste buds that can be accommodated on the tongue. Each ...
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1answer
105 views

Why does histamine cause bronchoconstriction?

What purpose does histamine-caused constriction serve in lungs during allergies and such, since it's vasodilator in other parts of body. Wouldn't it be more practical to vasodilate lungs so that white ...
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1answer
56 views

How are testosterone levels distributed among men and women?

Wikipedia tells me that men have 7 to 8 time higher levels of testosterone than women, on average. Since the hormone is linked with performance in certain athletic events, my hypothesis, which I ...
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2answers
76 views

Reaction of the body to heat

In massage school we are being taught hydrotherapy -- applying cold and heat to specific areas. It says that when applying cold, first the body goes through vasoconstriction, and then later ...
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4answers
782 views

Why does an increased heart rate mean increased blood pressure?

Say a person starts exercising. If their cardiac volume remains the same but their heart rate increases so that the overall result is an increase in cardiac output, will their blood pressure increase ...
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2answers
54 views

Is it impossible to increase skeletal bone mass, as opposed to just bone density? [closed]

I've heard exercise and resistance/strength training increases the density, but doesn't increase mass. So basically, experimentally or theoretically possible at least, can modern science do this/is it ...
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2answers
38 views

After how many hours water drunk is expelled from the body?

If one drinks a liter of water at 7 am when (in what span) will that water be eliminated through uresis? Is that process influenced by any factors such as empty stomach, sleep or other?
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36 views

Sulforaphane vs. Hyperthermic conditioning (sauna use) which would induce a greater heat shock response in the human body?

I’m curious to know which would induce a greater upregulation of heat shock proteins, consuming sulforaphane or putting the body through heat stress such as using the sauna. Sulforaphane reference- ...
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11 views

Can disorders involving involuntary muscle twitches and spasms have a hypertrophic and increased residual muscle tension effect?

Meaning disorders specifically like myokymia, myoclonus (positive and negative) and fasciculations. From the section of the literature I've seen, sometimes passing mentions are made when the disorder ...
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25 views

Why different people have different Sympathetic reaction

We all know that sympathetic mechanism is similiar in humans . Why people react differently for example one may ran after seeing a lion while other may keep standing or may shout without escaping ?
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1answer
65 views

Is it correct that the nicotinic acetylcholine receptor has nothing to do with Dopamin?

As I know Dopamine is almost exclusively produced via metabotropic receptors, is it possible for a nicotinic ACH receptor to influence a dopamineric neuron? Can a nicotinic ACH receptor cause a ...
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1answer
26 views

Can motor neurons in the brain stem start movements?

Supposedly (consciouss) movement is started in the cerebral cortex. But some time ago I've read a research which stated it might be possible some movements (not specified which ones, probably mean ...
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1answer
58 views

Does every protein starts with Methionine amino acid [duplicate]

During process of protein synthesis we need AUG Codon to start translation .As we know this codon codes for Methionine amino acid so can we say that every protein starts with Methionine amino acid ?
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1answer
721 views

Why clotting does not occur during Menstruation

As we know when we get injured our body's clotting systems stop the bleeding. So why does it take days for menstruation to stop ?
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1answer
69 views

Is it possible for human beings to feed through the nose?

There is a prediction on a futurology site that food can be eaten by inhalation https://2050.earth/predictions/smell-can-feed-you Although aerosol foods do exist they are still eaten by the mouth. ...
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0answers
17 views

In oscillometric blood pressure measurement, why do we assume that highest oscillations correspond with mean arterial pressure?

As far as I've seen, the point on the oscillometric curve where there are greatest oscillations represents the mean arterial pressure (MAP). My question is - why? What is the logic behind this ...
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1answer
40 views

How is fructose absorbed into the body

I’m finding contradicting methods of Fructose transfer to blood page no 264(10)One of which saYs fructose is absorbed by simple diffusion And another sources like this say that fructose is ...
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2answers
152 views

Why is urea not converted to ammonia in the body?

After the liver processes metabolites to produce urea and other by-products, these travel in the blood to the heart, then they are oxygenated, and some travel through the renal artery to the kidneys. ...
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0answers
62 views

Does our brain use up more ATP after smoking cannabis?

kind of an amateur here. If the firing of the neurons' signals uses up some ATP, and smoking cannabis makes them fire off more quickly, do our brains use up more ATP to sustain that rapid firing?
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1answer
49 views

human body in an environment where temperature is above body temperature

What would happen if humans were to live in an environment where the temperature is above the body temperature? Does the human body have a mechanism to cool the body? When the surrounding ...
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0answers
20 views

Pulse Oximetry, what significance does a decimal place hold?

I work in a sleep research lab. We have a couple of Masimo pulse oximeters that report pulse oximetry values in terms of integers (e.g. 90, 91, 92, etc.). Now our principle investigators used to use ...
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1answer
55 views

How deep could a human swim with SCUBA apparatus?

Using normal SCUBA apparatus and wet suit, how much pressure can the human body withstand? This is assuming that they descend as gradually as necessary for their body to make adjustments. What would ...
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2answers
846 views

Wim Hof Method claims Alkaline Blood is Good. Contradictions? Counterproof?

The Wim Hof Method claims, that it is beneficial to have alkaline blood. On the other site there is the medical claim that if the pH-value is not within the range of 7.36 – 7.42, enzyms are ...
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79 views

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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0answers
633 views

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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1answer
125 views

Where would vegetarians/vegans get a substitute of hemo/myoglobin from?

As far as I understand, there is a difference in the iron absorbed from meat than from other sources like grains and vegetables. If this is the case, is it possible that not ingesting the hemoglobin ...
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1answer
1k views

Is it possible to have sleep paralysis while sleepwalking?

At least from a conceptual level, these two disorders don't conflict. The effect of sleep paralysis is being conscious while having the inability to consciously direct motor functions. Sleepwalking is ...
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1answer
6k views

Ejaculation without orgasm: is this possible to do it at will without external stimulation?

I know that ejaculation without orgasm is possible for human males with external stimulations, e.g. prostate massage. My question is, can a human male perform full ejaculation without reaching orgasm ...
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1answer
111 views

Is there any way bicondylar/bigonial, bizygomatic or bitemporal breadth can change in adults?

Without cosmetic surgery or etc., are there any cases/example wherein a human adult has had a change in significance regarding these regions of the face? I have seen many anecdotes where people have ...
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0answers
12 views

Contracting mouth muscles as reaction to taking in specific food items

When eating very specific food items, especially confectionery like (salty) liquorice, (it feels as if) the muscles of my mouth contract, right when it hits my tongue. Does anyone know why this ...
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1answer
112 views

Can the heart generate its own rhythm independent to the SAN?

My textbook and a revision guide, which I believe is a reinterpretation of the textbook, state that: The SAN initiates waves of excitation that usually override the myogenic action of the cardiac ...