Biology pertaining to humans
3
votes
1answer
103 views
Can Naegleria fowleri enter through the eyes ( example rinsing/splashing eyes with water)
I understand that it primarily enters the body through the nose by by "feeding on the olfactory neurons in the nose" as answered here in a different question. Would the nerve cells in the eyes present ...
6
votes
2answers
803 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 ...
2
votes
1answer
61 views
Where are -HCl supplements absorbed in the human digestive system?
I see that quite a lot of drugs and dietary supplements sold in the USA have -HCl(hydrochloride) added to their name. For example pyridoxine hydrochloride for Vitamin B6. I'm interested in knowing ...
8
votes
2answers
297 views
Why do the two hemispheres of the brain control the opposite sides of the body?
Why does the left hemisphere control the right and the right hemisphere control the left? I googled it but didn't find a good answer regarding this. Could someone explain?
Does this adaptation help ...
0
votes
1answer
143 views
Why is offspring of identical twins not identical?
When identical twins marry identical twins, the children of the couples will be full genetic siblings but why are they not genetically identical?
7
votes
3answers
80 views
Adipocyte Density
People who are overweight and wish to lose weight, often do so because they are concerned about looking too big. Their increased size is attributed to an increased volume of fat.
When people try to ...
9
votes
1answer
73 views
Does sleep in humans re-structure based on the expected sleep time?
I've read about anecdotal evidence that human brain has a fairly good internal clock that can be used to judge the amount of time that has passed. I'm wandering if there are any mechanisms in the ...
14
votes
5answers
249 views
Are there any substance that are more dangerous at low dose than at higher dose?
It is commonly admitted that
The dose makes the poison
which means as a person, the more I take a substance, the more risk I take for my health.
There is even an indicator called LD50 (see ...
3
votes
1answer
747 views
Does mixing alcoholic drinks really make you more drunk?
There is plenty of anecdotal evidence ("beer after wine and you'll feel fine, wine after beer will make you feel queer") that mixing alcoholic drink types leads to a stronger effect, but I can't find ...
1
vote
1answer
108 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 ...
1
vote
0answers
70 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 ...
0
votes
0answers
25 views
Are there different metabolic pathways leading to “sleep”?
First of all, I apologize if this question does not belong on biology.stackexchange.
I've long been interested in sleep and recently postulated this question in light of reading about ...
1
vote
0answers
19 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 ...
0
votes
0answers
91 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
74 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
votes
1answer
185 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 ...
3
votes
0answers
73 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
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 ...
4
votes
1answer
35 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
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 ...
6
votes
1answer
391 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
154 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:
...
5
votes
1answer
136 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 ...
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 ...
8
votes
1answer
529 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 ...
10
votes
1answer
125 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
76 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:
...
9
votes
2answers
115 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 ...
-1
votes
1answer
1k 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
125 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
votes
1answer
249 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 ...
8
votes
2answers
150 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
104 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
41 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 ...
5
votes
1answer
3k 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
124 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 ...
8
votes
6answers
538 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' ...
0
votes
0answers
25 views
What's a good way to think of how a biological organism operates? [closed]
I'm a programmer and deal with computers a lot. I can write code and make computers do things, using conditional logic and algorithms. Not so long ago I started to research sleep and am trying to get ...
3
votes
1answer
62 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
169 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
163 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 ...
3
votes
1answer
146 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
124 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
votes
3answers
221 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
votes
1answer
43 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
78 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
186 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
187 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
260 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 ...
5
votes
1answer
81 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?
