Biology pertaining to humans
22
votes
3answers
3k views
How does the brain's energy consumption depend on mental activity?
What is the impact of mental activity on the energy consumption of the human brain?
I am most interested in intellectually demanding tasks (e.g., chess matches, solving a puzzle, taking a difficult ...
14
votes
4answers
1k views
How many genes do we share with our mother?
Somewhere I have read we share more than 99% of our genes with every other other person and 98% of our genes with chimpanzees. What does this mean? Don't we share 50% of our genes with our mother and ...
13
votes
2answers
241 views
How is temperature sensed?
Can anyone summarize the mechanism by which when an object of a given temperature is placed in contact with, say, the skin on a human fingertip, the average speed of the particles of the object is ...
4
votes
1answer
106 views
Which sex has higher variance of reproductive rate in modern societies - male or females?
Who has a more varied reproduction rate in modern western societies - men or women? The average rate is the same of course, but I wonder which sex have higher variance - higher variance means that ...
19
votes
5answers
439 views
Why do we age? or Do we have a theory of senescence?
There seem to be a number of ideas about why we age. Hypotheses include the gradual accumulation of cell metabolic products affecting organism function and the reduction of telomere length during cell ...
20
votes
3answers
2k views
Is there any advantage to one blood type over another?
All humans can be grouped into ABO and Rh+/- blood groups (at a minimum). Is there any advantage at all to one group or the other? This article hints that there are some pathogens that display a ...
17
votes
4answers
2k views
Death because of distilled water consumption
One of my friends said that I would die if I drank distilled water (we were using it in a chemistry experiment) I gave it a go and surprisingly did not die.
I did a bit of Googling and found this
...
4
votes
1answer
122 views
If fever is a natural immune defense, why do people take drugs to lower it?
If fever is a natural defense against pathogens, why do sick people take NSAIDs to reduce the fever?
20
votes
3answers
270 views
Is telomere length a reliable measure of health/lifespan?
Several companies are commercializing tests for telomere length such as this one here. I understand the basic mechanism for why telomeres shorten during DNA replication, but how good is the evidence ...
16
votes
2answers
234 views
Can an adult without genetic lactase persistence still develop a tolerance for dairy foods?
While investigating the rise of adult lactose tolerance, I came across the news that China has been encouraging its citizens to drink more milk, even though most of the Asian population lacks the SNP ...
14
votes
2answers
933 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 ...
13
votes
4answers
647 views
Can two humans with 44 chromosomes produce viable offspring?
It is known that there are very few individuals having 44 chromosomes, not the usual 46 chromosomes.
One example is a male in China: the first article, the second article.
The other is a female in ...
9
votes
2answers
353 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 ...
8
votes
6answers
521 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' ...
8
votes
1answer
273 views
How does laser surgery correct accommodation problems?
When someone undergoes laser surgery to improve eyesight, how does it correct accommodation problems?
Why does it not help presbyopia?
4
votes
1answer
845 views
What are differences between formation of embryonic disc in chick and mammal embryo?
Exam question which got lowest average points in my university: 1/5 average.
No markscheme available so my attempt below.
I assume that embryonic disk prefers to germ disk such that Formation prefers ...
15
votes
2answers
1k views
How do the brain and nerves create electrical pulses?
I have heard that information is sent between the brain and peripheral nerves via electrical pulses or signals, but I don't understand how they create them in the first place.
10
votes
1answer
104 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 ...
14
votes
2answers
619 views
How and where, in the human brain, are memories stored?
Background
I am a computer programmer who is fascinated by artificial intelligence and artificial neural networks, and I am becoming more curious about how biological neural networks work.
Context ...
14
votes
3answers
308 views
Are human fetuses more likely to be male?
Question: From a physiological point of view, when sex is determined in a human fetus, is it equally likely to be male or female?
Studies in this area typically measure age at birth, where the data ...
10
votes
1answer
295 views
Are human bodies programmed to die?
Following from this question: What is the evolutionary advantage of death?:
Is there any evidence that human bodies have systemic self-destruction built into their developmental program? I'm not ...
8
votes
1answer
941 views
Effects of Polyphasic vs Monophasic sleep in humans
Why do humans practice monophasic sleep cycles?
When altering one's circadian rhythm to a Polyphasic sleep schedule, how much would that affect development?
Is Monophasic sleep (once per day) ...
10
votes
2answers
121 views
What can the timing of human urination tell about the human's physical condition and circadian rhythms?
I've noticed a peculiar phenomenon. A subject drinks 400 ml of water, then observes time until the urge to urinate is felt. The time is 15 minutes. The subject releases water. 14 minutes later another ...
10
votes
2answers
258 views
Could an “overactive” brain increase the chances of Alzheimer's Disease?
From Raichle ME. 2010. Two views of brain function. Trends in cognitive sciences 14: 180–90:
Alzheimer’s disease (AD) is the most common cause of progressive
cognitive decline and dementia in ...
9
votes
3answers
1k views
Height and natural selection in humans?
I watched the documentary "Evolve" recently and in the segment on "size" Scott V. Edwards, Harvard evolutionary biologist mentioned the idea that humans might evolve to be 7' tall in 'hundreds of ...
8
votes
2answers
205 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. ...
8
votes
4answers
1k views
What is the armpit hair for?
Modern human beings, especially women, cut their armpit hair. It seems to me the armpit hair is trivial/useless. Shortly speaking, what is the armpit hair for?
6
votes
2answers
753 views
Which shades/hues of color are easiest to distinguish for humans?
I'm trying to represent data graphically and am using a variation of hue/lightness to distinguish one data point from the next. I would like to use a color that would allow me to convey most ...
5
votes
1answer
117 views
Can you consider a human as alive, or is it the cells on the body that are alive?
Sorry if this question seems strange, but in the recent time I have been interested in the question of what life is and how you can define life.
My question:
How long can individual cells live on a ...
4
votes
0answers
44 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 ...
4
votes
1answer
101 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 ...
16
votes
1answer
1k views
How does laughing gas (N2O) work?
Laughing gas (N2O), well, makes people laugh.
How does just a gas make us do that, there has to be some hormones at work...
So, I wanted to know how this works? What is the mechanism?
16
votes
2answers
232 views
Why would diffusion be faster across a non-specialised tissue?
The standard protocol for a person experiencing chest pains is to chew a 300mg aspirin tablet, the argument being that chewing rather than swallowing the tablet results in the aspirin entering the ...
14
votes
1answer
630 views
Why do we get runny noses in the cold?
The most annoying thing for me about being cold is a runny nose. Is there an advantage to having a runny nose when cold? What does having a runny nose achieve?
10
votes
3answers
255 views
Where does the 'C' in exhaled CO2 mostly come from?
When a human being exhales $CO_2$, what is, by the numbers, the main source of carbon atoms exiting the body in this way? I mean what class of cells, or which tissues are the biggest on a pie chart of ...
10
votes
1answer
335 views
Is there an evolutionary advantage to crying when sad?
It seems as though the act of crying when sad does nothing to relieve that sadness. Is there an advantage to crying from an evolutionary perspective, or is it the end result of a different process? ...
9
votes
1answer
158 views
Can Naegleria fowleri enter through wounds into the bloodstream?
All the sources I've read said that Naegleria fowleri enters the brain through the nose. But lets say that someone had cuts on their arm or leg and they are swimming in water that is conducive to ...
9
votes
1answer
88 views
Why is there an extended delay before G.M. liver cells are attacked by the immune system?
In this BBC article a trial is described where patients with B-Haemophillia are infected with modified Adeno-associated Virus 8 which contained the genes for Factor IX clotting protein. Trials seemed ...
8
votes
2answers
299 views
How does sodium in one's diet affect blood pressure?
Due to high blood pressure, my doctor has recommended I go on a low-sodium diet. So, that got me wondering what it is about sodium that drives this recommendation?
What does sodium do to a body ...
6
votes
1answer
35 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 ...
6
votes
2answers
192 views
Is there such thing as a generic “metabolic type”?
A while ago I picked up a book called "Eat right for your metabolic type". The book discussed the effects of the endocrine system on the overall shape and the speed of metabolism.
The book outlined ...
6
votes
2answers
106 views
What is the eye muscle status when you stare at distant view through a glass wall?
The book said when you look at object close to you, the eye muscles contract and vice versa. I wonder what will be the status of the eye muscles when I stare at distance view (such as a mountain) ...
3
votes
1answer
69 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 ...
3
votes
2answers
101 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 ...
3
votes
1answer
122 views
Could inhibition of progerin formation slow the rate at which a body ages?
According to wikipedia, progerin is activated in senescent cells. The protein itself is known to be the cause of a rare affliction 'progeria' - a disease marked by accelerated aging of the body. This ...
3
votes
1answer
164 views
Human sleep cycles and dream times, what influences the timing and intensity? Sleep history included
I'm doing sleep and dreams research and have developed an iPhone application to help me track my bedtime, rise time, sleep onset and also mark dreams. The app also monitors overall activity overnight ...
