This tag is for questions about the general biological features of human beings (as opposed to the biology of non-humans).

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1answer
146 views

Can a person die instantaneously from internal damage to the brain?

Given the human heart is autonomous, can a person die instantly from internal damage to the head/brain? I would expect the heart to continue to pulse until it ran out of energy ... My contention is ...
6
votes
1answer
252 views

Why is membrane potential not zero at equilibrium?

For the squid giant axon, the membrane potential computed by the Goldman equation is -60mV. And the Nernst potentials are (the differences between the K+ and the Na+'s Nernst potential and the ...
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0answers
37 views

Can we make any judgements about sleep or readiness to sleep from a heart rate metric and/or pulse oxymetry?

I'm looking at inexpensive and un-intrusive ways to quantify the state of human body/mind . One of these is Actigraphy, which is a study of human motion over time. This can be done with an iPhone ...
2
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0answers
243 views

Can the sleep/wake cycle be influenced by non-visible spectrum electro-magnetic radiation?

I've been reading a few papers on Melanopsin and Suprachiasmatic Nucleus (SCN), and see that the sleep/wake transition is ...
2
votes
1answer
119 views

How are memories stored in the brain?

I've been thinking about this for a while and I can't figure out how a memory can be stored in the brain. I understand that important memories are favourably retained, such as a near death ...
4
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1answer
279 views

In the vacuum of space would death be instantaneous?

I was arguing with my colleague about this matter (I'm not going to mention which side I fall on). Would death be immediate in the vacuum of space? For example, if I was suddenly teleported into the ...
6
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1answer
188 views

What is the effect of garlic on intestinal flora?

Now that we can compare whole microbiomes, has there been investigations on the effect of garlic (or diallyl disulfide, its main ingredient) on intestinal flora? From the proven antimicrobial ...
3
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1answer
234 views

How are melatonin levels measured in humans?

I'm wondering how it is possible to measure diurnal variations of melatonin levels in humans. I keep reading that there should be a large difference in amplitude between melatonin levels measured at ...
4
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1answer
46 views

Are there yearly variations in HIOMT (HydroxyIndole-O-MethylTransferase) availability?

I'm reading a booklet on melatonin published in 1996, titled "Melatonin and the Biological Clock". And see the following statement: HIOMT (HydroxyIndole-O-MethylTransferase), one of enzymes of ...
4
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1answer
96 views

What light intensity determines the start/end of a photoperiod in humans?

I'm reading this article, which discusses the influence of Long Photoperiod (LP) and Short Photoperiod (SP) on melatonin production: HIOMT drives the photoperiodic changes in the amplitude of the ...
8
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2answers
8k views

Why do vaccines cause your arm to hurt?

When you get a shot for a vaccine (for example, the annual flu vaccine), the nurse frequently indicates that your arm will ache for a day or two, maybe more. This ache is typically not just a pain ...
4
votes
1answer
475 views

Is there a relationship between Melatonin, Norepinephrine and depression in humans?

I'm reading a booklet on melatonin published in 1996, titled "Melatonin and the Biological Clock". This particular paragraph caught my attention and I would like to better understand what it means: ...
6
votes
1answer
256 views

Influence of alcohol on brain cells

As I am not related to biology, I would appreciate if you can keep your answers as simple as possible. My question is about the influence of alcohol on the brain. As far as I know, drinking alcohol ...
4
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2answers
119 views

Ultrasound during pregnancy

In a hospital I can see a long queue of pregnant women waiting for their turn for ultrasound. Is it safe to go through the ultrasound during pregnancy, especially during last few weeks? Is ...
9
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1answer
1k views

What determines testosterone exposure in womb, baby's genetics or mom's body?

I read this article which has the following quote: The ratio between index and ring finger is believed to be linked to exposure to the male hormone testosterone in the womb. And I wonder what ...
11
votes
2answers
189 views

Why do most breast cancers occur in women?

According to Korde et al. (2010): Male breast cancer accounts for less than 1% of all cancers in men and less than 1% of breast cancers. This raises the question: Why do most breast cancers ...
3
votes
1answer
166 views

What is the relationship between Homocysteine and Norepinephrine metabolic cycles?

I've been researching neuromodulators and have taken a look at the Norepinephrine/Noradrenaline system. The diagram of biosynthesis of Norepinephrine is presented in the wikipedia article: ...
8
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2answers
300 views

Does human digestive system benefit from eating same kind of food consistently?

Here's the reason why I'm asking: I've heard that it takes some time for pets(cats/dogs) to adjust to a different dry feed, where the new feed has to be mixed with the old one, slowly replacing the ...
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1answer
4k views

Ramifications and possibility of a diet consuming exclusively of human semen

Semen is a thick, nutritious liquid, rich in vitamins (such as C, B12), amino acids, lipids, monosaccharides (fructose), et cetera. Can semen's ability to fulfill the needs of human organism provide ...
0
votes
1answer
200 views

From which ancestor species did humans inherit orgasm?

From what ancestors did humans inherit orgasm? Do fish experience orgasm? Are the male and female orgasm the homologues that can be traced to the time when there was no difference in sex between ...
4
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1answer
1k views

What does vitamin B6 and B12 absorption depend upon?

I'm looking at my question about homocysteine metabolism and am doing a followup inquiry into vitamins B6(Pyroxidine) and B12(Cyanocobalamin). I've found this interesting bit about vitamin B12 and am ...
9
votes
2answers
248 views

Do twins “run in the family”?

My wife and I recently found out that we are going to have twins and so nearly everyone asks if we have a family history of twins. Now I know that the answer for me is that it doesn't matter—as ...
4
votes
1answer
484 views

Are there any effects of elevated Cysteine levels on cognitive function?

I'm looking at this diagram of homocysteine metabolism and see two distinct pathways that the amino acid may get metabolized to: with vitamin B12 it gets converted back into methionine, while with B6 ...
1
vote
1answer
57 views

What is the role of Homocysteine in cognitive function?

I'm looking at this link : Homocysteine and cognitive impairments and am looking for more information on specific cognitive impairments associated with elevated levels Homocysteine. That article is ...
8
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1answer
25k views

How many human cells are there in our body, on average?

How many human cells are there in our body, on average? Wikipedia says 1013: Bacterial cells are much smaller than human cells, and there are at least ten times as many bacteria as human cells in ...
3
votes
2answers
146 views

Is it possible to correctly identify presence of Y chromosome with external physical test only?

I asked a question related to the third sex, and I came to know that its always possible to categorize a human to male or female with presence of Y chromosome. Now, I have another question. Is there ...
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6answers
1k views

Human evolution: Where *exactly* did the first human come from, whose parents were not?

Layman here. So I have never really quite understood this facet of human evolution, (or any other for that matter), in that, I understand the evolutionary process, but I get lost on the 'border' ...
4
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1answer
80 views

Is there an advantage to having cellulite

There are many ads nowadays advertising cellulite removal, and it causes me to wonder if there is an advantage to having cellulite or if it is just a result of too much fat unevenly spread? Is it ...
4
votes
2answers
392 views

Does making yogurt from non-pasteurized milk work against possible disease bacteria?

In the past, when there was no pasteurization, could making yogurt from milk lower the chance of getting infected by bovine tuberculosis (or other diseases from infected milk)? For example, would ...
7
votes
3answers
226 views

What alternatives are there to the amyloid hypothesis?

Given the recent failure of the Bapi clinical trial, there is a lot of questions that have arised from he amyloid hypothesis. However, I can't really think of many other mechanisms that don't involved ...
4
votes
1answer
376 views

Why do rod cells not recover after bleaching upon exposure to bright light?

I'm confused as to why, when exposed to bright light, rod cells cease to function. I understand that exposure to bright light bleaches all of the rhodopsin, but...so what? Why doesn't the bleached ...
6
votes
1answer
350 views

What is Mendelian Randomization, and how is it used to infer causality in epidemiology?

Studies of human traits and diseases are inherently confined to observational studies, known as epidemiological studies. This can make it very hard to determine what actually causes a particular ...
10
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3answers
321 views

Athletes: nature vs. nurture?

Having watched a lot of olympians the last few weeks, I was struck by how many of them have actually spent their wholes lives/careers training for their one event (be in running a marathon, or ...
4
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1answer
70 views

During human ageing, which immune cell sub-types are most affected?

It is now well established that human ageing is accompanied by an increase in systemic, low-grade (chronic) inflammation, sometimes termed inflammaging (Franceschi, 2007). This is in part due to more ...
6
votes
1answer
130 views

Why are pilots under the illusion of gaining altitude without doing so?

We had a lecture about the balancing systems of the body (mainly the otolith organ / semilunar canals) in which a case was described where a pilot crashed into a ship. He was supposed to keep his ...
4
votes
1answer
540 views

When is the lactase in lactose-free milk active?

Recently we have started suspecting that one of our children has hypolactasia (lactose intolerance), and so accordingly I have had my first exposure to lactose-free dairy- and dairy-like products. In ...
2
votes
1answer
280 views

How does the brain instinctively know the math behind Newtonian Physics?

A 10 year old child does not have the intellectual power to accurately calculate the energy required to throw a ball an arbitrary distance. Yet they are able to accurately throw a ball at a ...
6
votes
1answer
547 views

Is there a biological basis to physical attraction?

Is there something encoded within us that makes us attracted to, e.g., someone taller or shorter with blonde or brunette hair with green or blue eyes? Or, is this phenomenon completely based on ...
6
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1answer
99 views

What is the biological mechanism linking temperature and probability to be infected with a virus?

It is common knowledge that when you're cold you could get a cold. What is the mechanism linking temperature and viral infection?
9
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2answers
563 views

Is there any biological reason that professional swimming is dominated by white people?

I suppose that the question should be turned around to "Why is it extremely rare to see black people competing in professional swimming?" because it is the absence of this phenotype while watching the ...
3
votes
2answers
128 views

What is the biological basis for a human's ability to think clearly and be aware while “fighting/competing”?

I'm interested in learning more about the biological systems or hormones or parts of the brain that affect short term (<15 minutes) ability to concentrate attention on the task and be aware of the ...
3
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0answers
99 views

What controls the feeling of discomfort/comfort before and after sleep?

I'm interested in which biological systems or hormones are involved in the following phenomenon: Before sleep it may be difficult to find a comfortable position, and muscular aches and pains are more ...
6
votes
1answer
58 views

On the effect of polluted air on health. Is it more gradual, or more immediate?

I've heard time and again that living in São Paulo (a large city in Brasil) takes 1.5 years from your life expectancy. The allegation is that this happens because of air pollution. I am just ...
4
votes
1answer
103 views

Is there a correlation between incidence of type 1 diabetes and vitiligo?

Does the data indicate that if you have one, the probability of you having the other is higher than that of someone who doesn't have the one?
1
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1answer
324 views

Is sperm contagious?

A person may have a cold or any other disease that is an airborne-infection. Is their sperm also contagious? Should the person take any precautions?
8
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1answer
442 views

A timeline of the odds for survival for fertilized eggs and fetuses

I'm looking for data to build a timeline of the odds for survival of a fertilized egg, i.e., What are the odds it'll last a week? What are the odds it'll last a month? 2 months? (and so on ...
8
votes
3answers
1k views

If body temperature is 37°C (98.6°F), why are most people more comfortable at around 21°C (70°F)?

It may be different for other people, but for me, anything above 32°C (90°F) is very uncomfortable, and my body is inclined to seek cooler temperatures. But I would think that at 32°C, the body would ...
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0answers
62 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 ...
10
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1answer
152 views

Does stress physically age our body?

Going by the assumption that stress eventually triggers a flight/fight response, and the subsequent realization that flight/fight puts the body in a system of readiness to use it's available resources ...
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0answers
169 views

How do the pharmacodynamics of the NSAIDs differ and are there “resistant” COX phenotypes?

I know that the non-steroidal anti-inflammatory drugs (e.g., aspirin, ibuprofen, naproxen) affect the enzymes cyclooxygenase (types I and II). Is there any difference in the degree to which these ...