Tag Archives: Human beings

Why is sore throat a symptom of many common sicknesses?

Your body is a castle. Germs are invaders. Your castle has thick walls but needs gates so you can see out of it, take in supplies and get rid of rubbish.

Gates are weak spots so get attacked more often. The throat is the most open to attack as it is moist, warm and we are constantly moving air (containing viruses/bacteria), food which we have touched with our dirty hands etc. across it.

The throat releases chemicals to make it swell up to deliver more blood (and therefore more infection fighting cells, nutrients etc.) to the site of attack. Swelling causes pain, presumably to make us go easy on parts of the body which are under attack.

Why do tablets sometimes feel like they are stuck in our throat after swallowing?

They’re kind of stuck. They’ll keep moving down your throat but that feeling means that the pill hit the walls of your esophagus when they were too dry so it’s harder for the esophagus to move the pill down.

Think of it like trying to go down a water slide. If the slide is wet you don’t get stuck and go very fast. If the slide is dry your skin creates friction and you go slow or get stuck. You need that lubrication of the water to go down fast.

If it’s a common issue for you try taking pills with a bigger sip of water. Let the pill float in your mouth for a second in the water then swallow.

Why are humans more energy-efficient in running than animals with four legs?

The really simple answer is that humans run more efficiently because we let gravity do a lot more of the work. When we go forward we’re basically putting one foot out and falling forward, then pulling ourselves forward and repeating the process with the other foot.

When quadrapedal animals run, they need to propel themselves forward with their front and back legs; the advantages of this are that they can put more of their total muscle mass into running and you get more sources of speed, and run faster/quicker; pretty much any quadraped can out-sprint a human. But humans are the undisputed champions of distance-running on Earth, partly because their run is more energy efficient.

The other thing that helps us run, just as a sidenote, is the fact that our bodies are really good at not overheating. A cheetah for instance can only keep up their vaunted 60 mph run-speed for a very short distance without overheating and exhausting themselves. But our ability to have the airflow of our forward motion wick heat away by evaporating sweat off of us is one of nature’s best heat regulation mechanisms, and allows for humans to run for hours on end without stopping, when properly trained.

Does the human body really have a 24 hour body clock?

Kinda, yes. We have a circadian clock, a biological mechanism that works by releasing certain hormones over a 24 hour period, as well as taking external cues such as the Sun. Without external cues, the circadian clock can actually run a bit longer or shorter than 24 hours, and in babies it’s still all messed up (which is why they have an irregular sleep schedule).

Not just humans have a circadian clock, almost every animal does.

This has nothing to do with leap years though, since leap years just add a whole day, not messing with our circadian clock.

Why do calories matter for losing weight but the weight of the food doesn’t?

Actually the weight of the food does matter, but not in the way that you think.

Food is composed of a bunch of different types of chemicals. Most has a fair bit of water in it which we urinate or sweat out after a while. Then there are proteins (building blocks that the body uses to grow or repair itself), carbohydrates (sugars and starches that the body burns to provide energy), fats (same) and fibre (which is the part that the body can’t digest and passes through).

Really only three of those ingredient types – carbohydrates, fats and proteins – are stored by the body for future emergency use and contribute to weight gain. They all become body fat or muscle, and they all contribute to the calorie count of food.

But food that weighs a lot but has really low amounts of those three types, like say celery, has almost all of its weight locked into water and fibre. It actually takes energy to go through the process of digesting food, so a celery stick or two actually helps with weight loss by both filling you up so you don’t eat as much other stuff, and consuming energy to process through your body.

Why do our bodies ache (joints, muscles, etc.) when we are sick?

One of the main reasons that our body aches when we are sick, like with a cold, is that the body’s immune system is producing plenty of antibodies in addition to the effects of all those viruses replicating in our cells killing them and leaving the area ‘raw’ and exposed.

These antibodies also promote the release of histamine which typically dilates (widens) blood vessels near an infection, this allows for more of the body’s defenses to get at the infection. There are histamine receptors in blood vessels that cause them to dilate.

As these chemicals are released into the blood stream they can end up in the muscles or other body parts. Various body systems can have receptors to histamine that can then trigger a pain receptor.

In addition to histamine there are biochemicals called cytokines that are released when the body has an immune response that are also known to trigger a  biochemical pathway that can affect pain receptors.

Histamine and cytokines releases can change the perception of pain receptors in the body making them more sensitive to pain factors.

There are other factors that come into play also such as biochemicals called interleukins that relate to fever conditions and temperature increases, all of which can affect pain receptors in different ways, for example heat receptors.

The overall perception of pains and aches over the whole body can vary from person to person and there may be other combinations of psychological,  physiological or even nutritional factors that may influence this.

Why is the liver one of the only organs that grows back when most of it is removed?

The best explanation right now seems to come down to two main factors.

1) Liver cells (called hepatocytes) have a relatively high rate of division in response to acute injury, which allows them to replace liver cells that have been damaged or are missing. This is similar to skin cells (fibroblasts and keratinocytes), but unlike, for example, heart cells (cardiomyocytes) which have an exceptionally low rate of division.

2) A special type of liver regeneration helper cells called “hybrid hepatocytes” were recently discovered by a group at UCSD, which appear to facilitate regeneration and reduce the risk of tumor formation (which can be an unfortunate side-effect of attempts at regenerative therapies).

Related reading:
Newly Discovered Cells Regenerate Liver Tissue Without Forming Tumors

What are the different blood types, and why can’t we mix them?

Blood types are determined by the presence, or absence, of certain markers on the surface of red blood cells, called antigens. An antigen is a molecule that is of sufficient size and complexity that the body can recognize it as “not self” and mount an immune response to destroy it as a potential invader. There are actually many antigens that can define various blood types but the most important come in two groups; 1) A, B, O, and 2) Rh.

Let’s look at ABO first. A and B are antigens that humans may or may not carry on their red blood cells, but the important thing about A and B is that they are also abundant in our environment, in microorganisms, pollen, and in animal dander. We are constantly exposed to the antigens and as a result, we develop antibodies that will attack and destroy red blood cells that are unlike our own.

We get one gene from each of our parents to determine our ABO type. The gene for A codes for the A antigen, the gene for B codes for the B antigen, there really is no gene for O, it’s more of a blood banker’s placeholder, it doesn’t code for anything at all. If you inherit two A genes you’ll be type A, but you’ll still type as A if you only get one gene for A and one for O.

Whichever way you get there, if you are type A you will carry in your bloodstream antibodies that will fiercely attack red blood cells displaying the B antigen. It goes the same way for people of type B. One copy of the B gene will make you type B if your other one is also a B or if your other is for O. Either way you’ll carry antibodies that will attack any cells showing the A antigen. Of course, you could get genes for both A and B and your type comes out AB and you don’t make antibodies against either antigen. People who are type O make both Anti-A and Anti-B antibodies.

Once they got the ABO grouping sorted out transfusions got a lot safer but still, people occasionally died in obvious transfusion reactions. Something else was going on. For the safety of the humans involved the search for the mystery antigen causing these reactions was done in Rhesus monkeys. People to whom the Rhesus monkey’s blood reacted to were dubbed Rhesus Positive, which got shortened to Rh+. People to whom the monkeys did not react are of course Rh-. Modern blood bankers refer to the Rh antigen as D.

The D antigen is uniquely human, it is not abundant in our environment, the only way for a person to become sensitized to, and develop antibodies to attack the D antigen is to actually be exposed to Rh+ red cells when they themselves are Rh-. The most common way for this to occur is not via transfusions it often occurs in childbirth. When a Rh- woman gives birth to a Rh+ child there is a risk the fetal red blood cells that make get into her bloodstream will be recognized as “not self” and an immune response will soon destroy all of the Rh+ cells, and any such cells her body may encounter in the future.

An ABO mismatch transfusion can be quickly fatal. An Rh- Rh+ mismatch is an entirely different matter. Of course, a Rh- woman of childbearing age should never be given Rh+ cells for the sake of the safety of future pregnancies, but in a life threatening emergency situation there is no reason a man of Rh- blood type couldn’t safely be transfused with Rh+ cells in sufficient quantity to reverse a trend towards death. This would be a once in a lifetime deal. Over several weeks all of the recipient’s transfused Rh+ cells would be destroyed for being “not self” and an enduring immune response would remain.

What are the negative effects of drugs like Ecstasy and Molly?

Ecstasy/Molly are MDMA.

Basically, MDMA activates a part of your brain which releases serotonin and that part is like a bank or a “holding space” of serotonin. Serotonin is also released when we eat chocolate, have sex or do something fun we enjoy and get that “happy feeling”.

When someone takes MDMA they release almost all of the serotonin in their bank, so it feels good and you have a great time because serotonin. Thing is, serotonin takes time to fill back up in the bank.

MDMA also acts as a psychedelic drug (a drug that can induce hallucinations or the feeling of expanded consciousness).

When people take MDMA regularly; like twice in a week or more, they don’t have the serotonin to enhance their “psychedelic experience”. So what was at one time this amazing, euphoric experience of feeling one with others and empathetic can turn into a nightmare where people feel they can’t escape it, until the effects ware off.

Some studies suggest long term regular use can cause long term permanent problems with serotonin regeneration.

Using pure/good MDMA occassionally (once/twice a year, spaced out from months apart) shouldn’t cause problems. Using it regularly can result in depression and possible brain damage due to serotonergeic damage.

What makes a melody sound happy or sad?

A musician could list you certain chords, rhythms or other structures that make music sound happy or tense or whatever. This is enough for the musician to know how to generate a certain emotional response, but it doesn’t explain why the emotional response happens.

The brain interprets everything through an extremely complex web of filters and processes. Some of that is linked to the amygdala, a part of the brain that is responsible for most of the emotional responses (e.g. fear). The amygdala responds fairly consistently (and thus predictably) to certain stimuli, which is why the same music will have very similar responses in most humans. To whatever extent that the response may be different, it’s due to the way in which memories and past experiences (which differ from person to person) are part of the processing.

This applies not just to music. It applies the same way to paintings, sculptures, stories and movies. Most people have a very similar basal reaction to the same scene or the same work of art, but whenever two people’s reactions are different, it’s because the work might trigger different memories or relate to different past experiences in each of them.