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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2
votes
2answers
31 views

Help reading chromatogram

A genetic variation is found in this chromatogram: It says that the "reference sequence" is the top line and that I can use the general genetic code to find the reading frame. I can see that there ...
8
votes
1answer
638 views

What causes knuckle “popping” and the feeling of relief that comes from it?

Many people like cracking their knuckles. I have always been curious about it. What happens when we crack knuckles? What creates the POP sound? Why do we get a relief-like feeling after doing it?
5
votes
0answers
47 views

Why do we get tired

At the end of a day full of work, it is general for people that their eyelids start to feel heavy. Laziness takes over and we begin to yawn. We all know that we're tired at that time, but why people ...
5
votes
1answer
59 views

What's a mouth ulcer/canker sore “made of”, and why do they develop?

Mouth ulcers are red/white rings with a crater. They are sore and last for 7-10 days. What I want to know is what they are 'made of' - i.e., what is the ring filled with, and why is the centre crater ...
2
votes
0answers
26 views

The ring formation of ringworm

I know ringworm is caused by a fungus on the skin, nails or scalp but what causes the rash to form as a ring instead of like a normal spread out rash?
3
votes
1answer
105 views

Why do people in the scientific community use terminology such as renal, hepatic, cardiac instead of kidney, liver and heart? [closed]

Why is there the need to map these everyday words into another set of words, it seems to complicate matters. Is it done mostly out of tradition or is there some logical basis to it?
7
votes
2answers
4k views

How does HCl not burn our stomach?

How does the digestive acid (HCl) not burn the surrounding skin of our stomach? It digests the majority of raw food we eat but how does it stay safely in our stomach? Also, how does the stomach ...
15
votes
6answers
2k 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
votes
1answer
90 views

Length of sleep time

Why do we wake up after 6-8 hours of sleep ? Why don't we sleep for lets say 20-30 hours ? What mechanism is it that controls when to wake us up and how does it determine the moment that we should ...
4
votes
2answers
797 views

Why do men have a higher hematocrit (red blood cell count) than women?

The hematocrit, also known as packed cell volume (PCV) or erythrocyte volume fraction (EVF), is the volume percentage (%) of red blood cells in blood. It is normally 45% for men and 40% for women. ...
6
votes
1answer
78 views

Time lapse between fresh blood's exposure to air and that same blood turning darker red-brown

For investigative purposes, I'm searching for a tool that can be used as a quick visual assessment of the the length of time that blood has been exposed to air after the blood flow has stopped.. Let's ...
4
votes
0answers
22 views

Do blood glucose “spikes” contribute to insulin resistance, or is prolonged elevation required?

There's increasing public discussion about the health risks of chronic insulin resistance* (IR). In many cases there's a focus on high glycemic index foods that "spike" your blood sugar, which implies ...
13
votes
3answers
4k views

Supercomputer Vs Human Brain

With supercomputers doing calculation in petaflops ($10^{15}$ Calculations per Second), have we crossed the speed of Human Brain?
0
votes
1answer
95 views

Why should or shouldn't we allow the human body to take its natural course? [closed]

For example, when you are sick but don't feel thirsty, this could be due to baroreceptor reflex that is attempting to readjust salt and water balancing. Why shouldn't a patient be left thirsty and ...
0
votes
1answer
40 views

Survival with only water but no food [duplicate]

How long can the average, healthy adult human survive with only water?
1
vote
2answers
43 views

Can leukopenia in a person with an otherwise normal immune system lead to non-infectious diseases in the long-term?

If a person has developed leukopenia as a side-effect of long-term use of anti-convulsant medications and his/her immune system appears normal otherwise (does not get infections any more often than a ...
7
votes
1answer
346 views

Why do people feel pleasure when using roller coasters / centrifuges?

The feeling when using an amusement park unit is usually a pleasure. Why is it not a pain instead? Are there advantages, from an evolutionary point of view, in loving this potentially dangerous ...
7
votes
4answers
193 views

How does an embryo know where to grow limbs etc

For example you have a cell or already a bunch of cells. Those cell(s) divide and after several week you have a grown organism, for example a human with limbs, several different organs etc. However, ...
4
votes
1answer
39 views

How can human infants express chymosin with only a pseudogene at their disposal?

I read on the Wikipedia article about Chymosin http://en.m.wikipedia.org/wiki/Chymosin It stated that chymosin is produced by gastric chief cell in human infants. But it also stated that human only ...
3
votes
1answer
607 views

What is the minimum air pressure the human body can tolerate if oxygen supply is not an issue?

Disregarding hypoxia, what is the minimum air pressure that the human body can tolerate? (i.e. at what air pressure would the blood start to boil, or skin start to burst, or whatever else might ...
11
votes
2answers
231 views

Why do we urinate more when we are nervous?

This question is a result of my personal experience... But I guess that is common for many of us. My school timing is 8:00 am to 1:30 pm (usually). During normal school days I typically urinate one ...
0
votes
1answer
17 views

Beta oxidation of saturated fats

In my text book there is an example of a 18 carbon long fat and it says that it can run 8 laps of oxidation. I don't understand why it doesn't run 9? 2 are removed each cycle? Thanks.
2
votes
1answer
990 views

Why does ear wax taste sour?

Why does ear wax taste sour? I am interested in both the physiochemical mechanisms and the evolutionary reasons behind the sour taste of earwax.
9
votes
1answer
288 views

Why gluconeogenesis?

It seems quite pointless to me. Why would I want to use energy to create a molecule that I can then use again for less energy? It seems only to serve as a complete waste of energy to me? Can someone ...
2
votes
1answer
30 views

How are ketone bodies used?

While searching for literature on ketone bodies, I can only seem to find how they are synthesized, but not how they are broken down. I'm looking for the series of events with enzyme names and ...
1
vote
1answer
39 views

Why use creatine phosphate?

We use creatine phosphate as an energy storage to resupply ADP with a phosphate group as our muscle cells only contain about 2-5 mM ATP. But why doesn't the muscle cells just keep 20-30 mM ATP instead ...
0
votes
0answers
29 views

Why doesn't the body optimize how many fatty acids it burns?

Ketone bodies are produced due to an excess of fatty acids being burned (accumulation of acetyl-CoA) so my question is: Why doesn't the body simply regulate how many fats it burns so it doesn't have ...
2
votes
1answer
26 views

NADH shuttles - Why cytosol?

Why is the malate-aspartate and the glycerol-3-phosphate shuttles located in the cytosol and intermembrane space? The krebs cycle happens in the matrix so why wouldn't they push electrons from the ...
2
votes
1answer
37 views

Atelectasis due to decreased surfactant in lungs

Surfactant is a protein lipid mixture produced by alveolar pneumocytes composed of Dipalmitoyl Phosphatidyl Choline lipid, apoproteins and calcium ions. This surface lines the alveolar epithelium ...
3
votes
0answers
28 views

Cholesterol's role in lipid uptake

I'm studying the digestion of fats and I understand that our dietary fats mostly consist of triglycerides. We absorb the fats and eventually they end up in a muscle/adipose cell for storage (as ...
5
votes
1answer
155 views

What is the maximum number of babies a human woman can have?

I know you could divide the female fertility period (~40 years, right?) by 9 months which would give something like ~50 kids (with no multiple kids per pregnancy). The limiting factor in this ...
4
votes
1answer
56 views

What happens when someone is stung by a jellyfish?

What happens in the human body when someone is stung by a jellyfish; namely a box jelly. Judging by what I have heard about the stings I'm guessing that they involve a neurotoxin. But what is ...
7
votes
2answers
120 views

Is it possible for a human to wake up in a wrong way?

There's an old folk saying that goes like "He got out of bed on a wrong foot" - to indicate that the person's day is going poorly because of the way that person woke up. Is it is possible for a human ...
3
votes
1answer
105 views

Can Leptospirosis be spread through human urine

I am wondering if Leptospirosis can be spread via the urine of an infected human individual. All of the sources I have been able to find on the web have stated that the disease is primarily spread ...
4
votes
1answer
2k views

Difference between intervertebral and vertebral foramina

In the human spine, what is the difference between intervertebral and vertebral foramina? Is it just a matter of perspective and do they refer to the same thing or are they different?
0
votes
2answers
75 views

Difficulties understanding a pathway [closed]

I am not a biologist and I would love to understand what is going on with this pathway. I went to the description but it's still complicated, and I couldn't follow. Can someone please help me with it? ...
20
votes
4answers
2k 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 ...
1
vote
1answer
27 views

Pasteurization and Bioavailability of Antioxidants in Beet Juice

What are the effects of pasteurization on the antioxidants found in beet juice ? Does the process render most of the beneficial nutrients (betaine) useless and make them unable for the body to process ...
8
votes
2answers
132 views

Should we induce fever to assist healing?

I am currently reading "The Fundamentals of Anatomy Physiology" 10th edition, and have found it an incredibly interesting book. I have just been reading about the lymphatic system, and the various ...
9
votes
3answers
4k views

Why can all animals swim in water without learning to swim but humans cannot?

I had a question since I was a child. I was always curious about the fact that all animals can swim in water. They don't need any training or to learn swimming. But humans need to learn to swim. Why ? ...
3
votes
1answer
209 views

Possible genotypes for blood types?

If I am blood type B, what are all the possible genotypes that could be expressed by my parents? I think it might be 16 but I was reading online and saw this: Similarly, someone who is blood type ...
1
vote
2answers
76 views

How does the body respond to blood donation; are there any possible risks?

Can blood donation cause any harm to the donor? I have been told so, but cannot find any references supporting this claim. I have also learned that our body will replace the lost fluids within 24 ...
7
votes
3answers
12k views

Why do toenails grow much slower than fingernails?

As the title suggests, I've noticed that my fingernail grow much faster than my toenails. For instance, I usually trim my fingernails every two week or so, but for toenails the number would be about 6 ...
0
votes
1answer
38 views

What would happen if we had a device that produced oxygen inside of our lungs? [closed]

Hypothetically speaking, suppose there is a device that produces a limitless supply of oxygen. The device is inhaled by a human and is resting inside the (a) lung. What would hypothetically happen if ...
5
votes
1answer
72 views

Are some facial features more important than others in human facial recognition?

I'm often surprised by the human ability to correctly identify other individuals despite significant modifications due to ageing, hairstyle, injury, etc. But, sometimes the addition of a beard and a ...
19
votes
3answers
3k views

Is there any use of CO₂ in human body?

We all know CO₂ as a waste product of metabolism . Does CO₂ have any helpful role , apart from having a role in pH of blood ?
2
votes
1answer
73 views

Role of Calcium and Magnesium in capacitation/acrosome reaction

During the acrosome reaction, the activation enzyme present in the sperm dissolves the corona radiata and zona pellucida enabling the sperm to reach the plasma membrane of the egg. Also calcium and ...
4
votes
2answers
2k views

Why does yawning impair hearing?

When I yawn I can't hear anything happening around me. I also feel some kind of muscles inside my head contract and hear a faint hum, but it is not loud enough to explain not hearing other sounds. I ...
20
votes
4answers
3k views

Where does the 'C' in exhaled CO₂ mostly come from?

When a human being exhales CO₂, 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 ...
11
votes
6answers
3k views

What is the use of eye banks, if eyeball transplants do not exist at present?

Corneas are donated and transplanted, but not the eyeball. I don't understand. What is the purpose of donating a cornea without an eyeball to a blind person?