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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11
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2answers
2k views

Will humans and animals be harmed by frequencies outside their hearing range?

The human ear (for example) is sensitive to frequencies from 20Hz to 20kHz. Any sound beyond that limit would not be heard by us naturally. Will it harm us (effect our ability to hear) when we hear ...
3
votes
0answers
36 views

Can a sound frequency 'not' within human hearing (20 Hz - 20 kHz) damage hearing when it is of high volume? [duplicate]

We can't hear sounds outside the range of 20 Hz - 20 kHz. However, if an inaudible sound is played at high volume, will one's hearing be affected?
1
vote
1answer
87 views

What in soy are people allergic to and will these allergens be passed along if an animal that has eaten soy is consumed?

I have two related questions about soy allergies and possible reactions. What is it that are humans who have soy allergies actually allergic to? What is the allergen? If an animal eats soy, are ...
1
vote
0answers
33 views

Are anti-inflammatories useful for tendinosis? [closed]

I am wondering why some doctors prescribe anti-inflammatory treatments for conditions that are supposedly not inflammatory such as tendinosis. From my understanding, only tendinitis a swollen tendon ...
8
votes
1answer
231 views

What prevents a pregnant woman's immune system from recognizing her fetus as nonself (and attacking)?

I'm familiar with the scenario of Rh- mother with Rh+ fetus having complications (more so after her first child), but that's not what I'm curious about. I want to know mechanistically why a pregnant ...
1
vote
1answer
71 views

Are there any studies of epigenetic difference between twins during their lifespan?

Are there any studies of epigenetic difference between twins during their lifespan ? I ask because I wonder if there exist phases during lifespan, when environmental factors plays major role ...
4
votes
1answer
265 views

Does frequency of eye blinking reveal anything about human biology/nervous system?

I'm looking at an output of a single dry sensor EEG headband with the sensor positioned above left eye. As a side effect of it's placement, the device picks up eye blinks, and some eye motion as ...
5
votes
3answers
175 views

What are the limitations of commercial-grade DNA genotyping compared to full sequencing?

I've heard about services like 23andme, which offer genetic testing to the general public. As a person who knows very little about genetics, I'm interested in the subject and would like to know what ...
4
votes
1answer
179 views

How can the child and the mother have different blood types?

As far as I know the fetus is fed by the umbilical cord which basically connects his/her circulatory system with the mother's in order to supply oxygen and nutrients. But how is this possible if they ...
0
votes
1answer
201 views

Are lactic acid and prolactin rise after exercise connected?

I've been reading about prolactin, a human hormone. Apparently it's levels within the brain can raise after exercise, although the mechanism is not clear to me. I'm interested of there is any ...
1
vote
1answer
75 views

Is it possible to give a person an allergic reaction in a very specific place?

Can I give a person an allergic reaction at a very specific spot in a tissue? And if so, how accurate can i get?
1
vote
2answers
206 views

Why does throat 'burn' when you've got a common cold?

Apart from pain when swallowing, there's also a persistent feeling of throat 'burning' in the same area. What causes it and why does it feel that way?
2
votes
1answer
53 views

Trigger allergic reaction in non-allergic people?

Is there a proven way to trigger an allergic or allergic-like reaction in non-allergic people? I have wondered if this is possible, since allergies are basically just a form hypersensitivity - so ...
3
votes
1answer
161 views

Does an allergic reaction kill body cells?

I have wondered what actually happens in an allergic reaction that causes the symptoms such as pain, rash etc. Is it possible that the human body actually kills its own cells in the process?
0
votes
2answers
48 views

Manipulating Gut flora in vivo

I am tasked with designing an in vivo experiment in humans that requires manipulating the gut flora in one sample group to gauge its effect. Please suggest ways of doing this besides administering ...
10
votes
3answers
354 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 ...
1
vote
1answer
113 views

Interlocus Contest Evolution means suicide?

I was reading Matt Ridley's "Genome" book. I am trying to understand the Interlocus Contest Evolution in his X-Y chapter. I do not understand why the X and Y chromosome would want to kill each other. ...
6
votes
2answers
439 views

What is the relationship between migraines and histamine?

A family member suffers from migraines so I have been reading a little around the subject. There seem to be any number of "triggers", but I have seen mention several times of the role of histamine ...
4
votes
1answer
108 views

Why do we yawn?

I've read a new study which suggests that yawning may help you keep a cool head. Also, the findings might hold some hope for sufferers of insomnia, migraines, and even epilepsy. Is there any ...
3
votes
1answer
241 views

The fundamental importance of R.E.M. Sleep. (Rapid Eye Movement)

Question: I know that experiments have been conducted to determine the importance of R.E.M. sleep in our sleep cycle. It is particularly important for learning, information synthesis, and recovery ...
2
votes
1answer
127 views

Why do cells have an average 'life span'

I've heard of Henrietta Lacks. As a result of a genetic mutation, her cells never died. I've heard/read that overtime, our cells stop multiplying as much, (as an effect of aging). Why? Why do we age? ...
6
votes
1answer
248 views

Is there a normal human melatonin concentration to light level curve?

I'm looking for a graph or a curve that would show the typical concentration of melatonin in blood or saliva for humans over 24 hours. It would be good to know the photoperiod for the same human as ...
2
votes
1answer
109 views

Why do genitals feel frozen when freefalling?

I don't want to add much more about that. Since childhood I noticed a chilling effect, even when doing rollercoaster-type activities.
3
votes
1answer
127 views

Where does all the food go?

Food goes in, excrements come out. This seems obvious. But it seems like the mass of the excrements is less than the one of the food. Most people I asked answered: "There's a difference because it's ...
4
votes
1answer
114 views

What kinds of arousal can a human brain experience?

I've been reading about the new phenomenon called "arousal addiction". The context in which this term is used is Internet, Porn and/or video game addiction(cummulatively Internet Addiction Disorder - ...
4
votes
2answers
293 views

Effects of exercise on the brain

I am well aware of the phenomenon of neurogenesis induced by exercise, as well as the dopamine release that results from exercise. I am really interested in neuropsychology and the effects of exercise ...
8
votes
1answer
1k views

What influences the timing of human bowel movements in the morning?

I'm trying to understand if the timing of human bowel movements in the morning is associated with the circadian rhythm, and can thus be used to make predictions about the circadian rhythm. What ...
6
votes
1answer
98 views

Does artificial heat (shower/tea) affect diurnal rhythms in humans?

I've been reading that over the course of the day, human body temperature follows diurnal rhythm with the lowest body temperature observed some time close to the middle of the sleep episode, while the ...
2
votes
1answer
65 views

Do siblings have a bias toward believing they look different from each other?

Anecdotally, I have observed (myself included) that siblings tend to think that they look less similar to each other than an unrelated observer would say. Is there any experimental data to back this ...
9
votes
1answer
78 views

Are homozygous carriers of the CCR5-Δ32 allele fully immune to all known strains of HIV?

Or is there documented evidence of even one homozygous carrier contracting HIV and staying infected?
3
votes
2answers
2k views

What is the inlet/outlet speed of air going in/out of our mouth during inhalation/exhalation

During inhalation, your alveoli expand, creating a pressure difference between the atmosphereic pressure and our lung sacks and therefore air will flow into the repspiratory airways. I am trying to ...
1
vote
1answer
50 views

Does difference in expected life duration between men and women have biological nature?

It is known that men in most countries live less than women. I wonder whether it is due to different life conditions or because male and female organisms differ? For example, I heard that ...
6
votes
2answers
9k views

Can positive and negative blood type of a couple lead to miscarriage?

I want to know can $+ve$ and $-ve$ blood group of a couple could be a cause of miscarriage in pregnancy?
8
votes
1answer
10k views

What is the composition of human feces?

Are there any studies or general information on the composition of human feces? I'd specifically like to know the percentage of carbohydrates and amino acids relative to the amount that was ingested ...
17
votes
1answer
1k views

Is kissing a natural human activity?

The word natural here is meant in contrast to it being a sociological construct. Is kissing in all its forms something natural for humans? Is it instinctively erotic? Or is it just a conventional ...
4
votes
2answers
159 views

What is the purpose of the adrenal medulla?

The adrenal medulla is less of a 'real' endocrine organ like the others in the endocrine system and much more an extension of the sympathetic nervous system. In fact, its chromaffin cells are modified ...
5
votes
1answer
63 views

Is the eyes' movement discrete?

When tired and it was dark, I noticed that if I focused on a dim light source and moved my eyes fairly rapidly sideways, the resulting images that lingered for a short while were not smoothly blurred ...
5
votes
1answer
1k views

How much gas is exchanged in one human breath?

When we breathe, our lungs absorb a portion of the oxygen in the air, and replace it with some amount of carbon dioxide and water vapor. Typically, how much $O_2$ (in grams, milliliters, or moles for ...
6
votes
2answers
156 views

Is warmth/temperature sensed linearly or on a different scale?

I understand that the atmospheric temperature is sensed relative to external body temperature. However, is the sensation of warmth registered linearly, or is it on a logarithmic scale, similar to ...
2
votes
0answers
42 views

Is there an entry-level circadian model of serotonin, ghrelin, dopamine and the sense of well being?

I've long been interested in circadian rhythms and recently came across a variety of articles that appear to indicate that the following neurotransmitters, transferases and hormones are connected. ...
2
votes
0answers
87 views

Why do people feel extreme cold at different temperatures compared to other people of same body structure?

I have seen some people shivering in the room temperature of 18°C while others of similar body structure do not feel that much amount of cold. Of course the clothing of both people is similar if ...
4
votes
1answer
132 views

Are serotonin levels in humans affected by light?

I'm reading this Wikipedia article on light therapy and noticed a peculiar statement: The production of the hormone melatonin, a sleep regulator, is inhibited by light and permitted by darkness ...
1
vote
1answer
72 views
5
votes
2answers
5k views

Why can't you taste food when you have a cold?

It is a common observation that food is tasteless when we have a cold. Why is that so? What is the cause of inability to taste when we have a cold? Are the nose and ability to taste connected?
2
votes
1answer
66 views

Are humans hardwired to continue gathering resources after the costs outweigh the benefits?

An animal will stop foraging in a berry bush if the perceived cost of searching for berries remaining is greater than the cost of finding another bush which isn't as picked over. People do the same ...
-2
votes
1answer
91 views

Good place to ask health based questions? [closed]

I like the development of biology.stackexchange.com, but it is still in an early stage and far from perfection. While we develop it further, could you guys help me finding places to ask questions ...
6
votes
3answers
694 views

How to map the Gene name to its Gene Symbol?

I am learning in Gene data lately so I apologize for the silly questions in advance. I read a paper for a cancer on human which found some important genes. For example, the paper listed one of genes ...
7
votes
3answers
3k views

Can a human smell through the ears?

The title does, prima facie, appear absurd. Performing a swallowing action whilst pinching the nostrils shut gives the impression of listening through a bucket filled with water around the head; ...
8
votes
2answers
788 views

How much weight/volume do microbes occupy within the human body?

Microorganisms constitute the bulk of all the biomass on Earth. I weighed myself yesterday, and wondered how much less I would weigh if I were completely free of bacteria and microbes, inside and out. ...
4
votes
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 ...