The study of the normal function of living organisms and the means by which it is achieved.

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What gaseous substances do humans emit?

Other than CO₂ and Methane what other gases do humans produce or emit? For example, does skin decomposition, or aerobic respiration emit any special gases that people don't normally realize or know ...
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2answers
96 views

Why do small organisms make faster movements than big organisms?

I hesitated to ask this question because it seems so obvious and intuitive. However, I am not able to explain this tendency. Background It seems to me that small organisms make faster movements than ...
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1answer
43 views

All or nothing phenomena

We know that an action potential is produced by an active cell membrane when the stimulus reaches a certain threshold. When it does, an action potential fires, and when it doesn't, nothing happens. ...
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1answer
74 views

How do animals handle light refraction in different media?

For a human, when diving underwater, everything is blurry because of the water's different refractive index compared to that of air, which we are accustomed to. How do animals, like turtles, seals or ...
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2answers
1k views

How do we know the presence of light when our eyes are closed?

Last night I laid on my bed and tried to go to sleep with the light off. I closed my eyes (but hadn't gone to sleep). My younger brother touched the wireless mouse (which had laser) for the laptop. ...
13
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1answer
84 views

What is the mechanism responsible for the periodicity of hiccups?

Hiccups (singultus) are caused by involuntary spasm of the intercostal muscles and diaphragm, producing a sudden inspiration with associated glottic closure. It seems the neurobiology of the reflex ...
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1answer
47 views

Normal position of Electrical axis only in the III lead?

I found this sentence in my notes which is not exact enough: Electrical axes Excitatory processes have definite direction and magnitude and could therefore be represented as vectors. At ...
0
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2answers
68 views

Can you disconnect sensation from the brain without destroying muscle functions?

I want to know if it would be possible for a surgeon to "shut off" a person's senses without causing paralysis of any kind. The person would have to maintain their ability to speak and move, but not ...
3
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1answer
55 views

Mechanisms of bone growth

The length of a bone is caused by growth of hyaline cartilage which is then replaced by bone tissue. How do cells know whether they should grow the hyaline cartilage? What are the key molecules that ...
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0answers
39 views

Biology Experiment Data (Hodgkin-Huxley)

I'm doing research into the Hodgkin-Huxley Model from an electronics/mathematics perspective and I'm looking to find actual numerical results from experiments on squid axons. I want to compare the ...
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1answer
48 views

Normal Frequencies in Heart

I am trying to visualise possible ranges of frequencies from different structures of heart: different valves and their possible frequencies heart sounds I - IV and their normal frequencties what can ...
3
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1answer
252 views

What are the highest and lowest possible pH, paCO2 and HCO3 in the blood of living human?

What are the highest and lowest possible values of pH, $paCO_2$, and $HCO_3$ in the (arterial or venous) blood of a living human being?
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2answers
1k views

Do women have testosterone?

In a documentary on fitness I saw it was stated that women can't get big like men because of their low concentration of testosterone. If it is true that women have testosterone, where is it made? Why ...
2
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1answer
37 views

Kinesiology Tape Benefits

Recently, kinesiology tape has become popular, especially in CrossFit. I have also noted its' use in the NFL, and I want to say Tennis as well. What beneficial effects does this tape offer our bodies ...
6
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1answer
6k views

What is the normal duration of human sexual intercourse?

Wikipedia is saying: Men's typical ejaculatory latency is approximately 4–8 minutes How the researchers measured this? How did they know if the test subjects weren't suffering from premature ...
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1answer
28 views

What triggers the release of gonadotrophin-releasing hormone with the onset of puberty?

I am interested to know the process of development of puberty. During puberty, when boys/girls reache 12-14 (puberty) years of their age, their hypothalamus releases gonadotropin releasing hormone ...
4
votes
1answer
108 views

Counterintuitive action of Vitamin D?

Vitamin D acts in a way which to me is counterintuitive. It functionally supplemets Parathormone. It in the intestinal tract steps up calcium absorption by altering nuclear gene expression and also ...
4
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2answers
202 views

Where do the 31 spinal nerves start/meet?

Which part of the brain is the first place (from top to bottom) where all 31 pairs of spinal nerves (on each side) meet? Or if they all start at one place - where is that? Nominally, the beginning of ...
4
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1answer
94 views

How efficient is the human body at metabolizing food?

My friend and I were having a discussion over how "efficient" human digestion is. If a human ate a 1000 calorie hamburger, how many of those calories (how much energy) does the body process into ...
22
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3answers
3k views

What actually happens when my leg 'falls asleep'?

Most people have experienced the temporary loss of feeling and tingling in their leg resulting from sitting in an abnormal position for a short while. Usually you get a loss of feeling in your leg ...
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1answer
70 views

brain activity responsible for imagination

Which part of brain is responsible for advance or unseen imagination For example:ones brain can make a situation in mind which is impossible to happen ...which part of brain is hyper active?
3
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1answer
249 views

Why do I breathe out of BOTH nostrils?

After reading the question why do I only breathe out of one nostril I realized that breathing out of both isn't common. I have always breathed out of both, and when I get a stuffy nose, or a runny ...
5
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1answer
39 views

Components of the concept of Developmental Noise?

Developmental noise is a concept that correspond to the amount of possible phenotypic variance of a given genotype in a given environment. Intrinsic noise (aka Cellular noise) is a component of ...
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3answers
1k views

Why are there no organisms with metal body parts, like weapons, bones, and armour? (Or are there?)

Reading this question, Why are there no wheeled animals?, I wondered why no organisms seem to make use of the tensile and other strengths of metal, as we do in metal tools and constructions. I am ...
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2answers
235 views

Why does a blood test show ethanol when no alcohol was consumed?

Why would ethanol show up in a blood test if a person had not been drinking alcohol in many years. What are other reasons for showing ethanol?
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1answer
31 views

Characteristics of radius of blood vessel

Which properties do determine the radius of blood vessel? I have these thoughts distension, elasticity, contractility and cross-sectional area of the walls. Is there any other properties?
3
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1answer
460 views

How is Hypertonic Urine Produced in a Mammalian Kidney?

I know that the ascending loop of Henle is impermeable to water and ions, and, by end of the ascending limb, the osmolarity of the tubular fluid is very low due to the active transport of ions out ...
2
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1answer
35 views

What's the mechanism behind 'losing heat through your extremities'?

I can understand how if you are not circulating enough (warm) blood, by not moving much while in a cold environment, your extremities themselves lose heat, and become cold - but I don't understand how ...
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1answer
93 views

Are there any situations in which phenylephrine is preferred to pseudoephedrine?

In the mid 2000s in the US, due to issues of drug enforcement, pseudoephedrine containing medications were brought behind the pharmacy counter and in most cases require ID, and phenylephrine was ...
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2answers
351 views

Negative role of Placenta

How can a placenta turn hostile to the mother or fetus ? What are the abnormalities found during placental delivery ?
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0answers
12 views

What biological processes are affected by dietary fiber besides peristalsis?

Dietary fiber affects the rate of peristalsis, but what other effects does it have? Does fiber affect signal transduction, hydration, the autonomic nervous system, organ function, other biological ...
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2answers
4k views

How does extracellular potassium ion concentration and calcium ion concentration affect the excitability of a cell?

When extracellular $K^+$ concentration increase by a certain amount, excitability of cells is higher because the resting potential shifts toward a higher equilibrium potential of $K^+$, therefore ...
3
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2answers
128 views

What are the factors that control the speed of propagation of neuronal signals?

If we consider an analogy between a wire and a neuron there may be some resemblance between the factors controlling the data flow rate. For example the increased width of wire leads to decreased ...
2
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1answer
244 views

Why does caffeine consumption cause one to urinate more?

What is the physiological mechanism behind the diuretic effect of caffeine?
2
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1answer
82 views

Why does the arch of aorta coils?

My study materials use the word vesselcompression chamber of aorta to emphasize aorta's elastic property. The arch of the aorta only coils, not its straight part. I think the reason why the arch ...
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1answer
34 views

Why is Aorta sometimes called Compression chamber?

I find this statement that Aorta is called Compression Chamber in my study materials. Aorta can it keeps blood flowing it can accumulate potential energy for bumping and compression However, why ...
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2answers
781 views

Why there is a very high drop in pressure from arteries to arterioles?

Laplace law explains why the pressure is the same in aorta and arteries (100). I am thinking why there is so big drop in pressure when going from arteries to arterioles (40-60). Why there is a great ...
4
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3answers
154 views

How does strength of a pulse related to EKG(ECG)?

There are variabilities in the heart rate as well as strength of heartbeats. I want to know if one can predict which heartbeat will be strong or weak based on the corresponding EKG/ECG signal. I am ...
7
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5answers
333 views

Why is the human body able to repair a broken bone and not a heart muscle?

The human body can repair skin/organ laceration, fractures, even repair nerves - albeit the duration and rate of recovery differ. For instance: The burn scar on my arm from the hot soldering iron ...
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1answer
54 views

Gastro-intestinal physiology reference

I am a physicist but I have always wanted to understand how my digestion takes place in as much detail as possible. I have no idea about books or reference on the subject of Gastro-intestinal and ...
12
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3answers
2k views

Why is high fructose corn syrup unhealthy?

I understand that high fructose corn syrup was found to have detrimental effects on peoples' health. Why is this so?
2
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3answers
2k views

What organs are absolutely needed by the human body?

The title is my question: what organs are absolutely needed (fatal if injured/removed) by the human body and perhaps animals in general? I'm not asking which organs are mechanically replaceable, but ...
2
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0answers
48 views

Relationship between mN and mg in vessel contraction studies?

What is the relationship between mN and mg as the units involved to measure the changes in contraction? A tool most widely used is an instrument called myograph. In these exoeriments, either units of ...
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1answer
30 views

What are the movement mechanisms of thrombus?

I am thinking how thrombus (veins, arteries and heart) can move. Secondary mechanisms come to my mind only: some enzyme which lyses it, probably adhesion mechanism. Blood circulation (flow rate) ...
10
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3answers
1k views

Do men have more extreme variations than women?

This question was considered unsuitable for Skeptics and I think it is more suited to BIology than Cognitive Sciences I was reading this article which I found interesting. It is not supported with ...
2
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1answer
71 views

Inductance in cell

In an animal cell, especially neuron and in particular its axon, while there is electrical resistance and capacitance mechanism in the cell, which play essential roles in the cable theory model of ...
7
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3answers
196 views

Where does extra blood come from to fill your muscles during exercise?

Let's say I go to the gym and lift some weights an hour. During this time my arms will grow due to the "pump" -- the extra blood rushing in to feed the muscles. For example, I've measured about 2-3 ...
3
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2answers
80 views

Is vision a vestigial sense for deep ocean species?

Sunlight doesn't penetrate beyond a couple of hundred feet from the surface of the ocean. Species that exist at greater depth probably live in a state of perpetual night; yet from a quick google image ...
5
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1answer
81 views

Competition for mates in sea horses

This source here ...research has shown that it is STILL the males that compete for females. says that male sea horses compete for mates but this source here Females exhibit a ...
2
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1answer
35 views

What makes certain obligate anaerobes viable in fermentation starter cultures?

If Propionibacterium are obligate anaerobes (to wit, poisoned by oxygen), what makes 'Dairy' or classical propionibacteria (e.g. P. shermanii, P. jensenii, P. acidicpropionici, et al) viable in ...