6 When we stay in the water for too long, our skin gets wrinkly. This is not because of water entering the skin but is due to a nervous system reaction that contracts the blood vessels when underwater for better skin grip.

It is commonly believed that when a person stays in the water for too long, the skin absorbs water. This makes the skin look all wrinkly. But that is not the case. Since the 1930s, researchers have known that the reason for skin getting wrinkled in water is the constriction of blood vessels below the skin. But, they could not pinpoint whether this had any significance.

Mark Changizi, an evolutionary biologist, came up with an explanation in 2011. He and his team suggested that the wrinkling mechanism must have an evolutionary significance. He further added that the pattern of wrinkling seems optimized to improve the grip on the water. They even carried out experiments that proved this scenario. (source)

7 The shiver that we get before getting cold is actually a series of neural signals that the brain sends to the spinal cord telling the muscles to speed up their contractions. This, in turn, increases body temperature.

A shiver is a sign that a person is cold, but there is an amazing science behind it. Shivering is a reflex triggered by the brain to let the body know that it’s cold. The reflexes are a series of neural signals that travel down the spinal cord to the areas that are getting cold.

Once the muscles of the body realize that they are cold, they start contacting at vigorous speeds. These contractions produce heat that warms up the area. The more muscle activity, the more heat is generated. (source)

8 Every three to four days, the stomach develops a brand new lining. This is done so that the hydrochloric acid secreted for digestion is kept away from digesting the stomach itself.

The stomach is a hollow organ with a very strong lining known as mucosa. Cells in the mucosa produce hydrochloric acid that breaks down and digests food. The acid in the stomach is so concentrated that if a drop of it falls on a block of wood, it would cut right through it!

With such concentrated acid, it is quite imperative that the lining of the stomach has to be quite fierce. To ensure that the acid does not reach the structural walls of the stomach, the mucosa gets refurbished every three to four days.

In some people, the replenishment of the lining does not occur in time. This leads to acid seeping through the damaged lining onto the stomach walls. Such people suffer from gastric ulcers. (1, 2, 3)

9 The feeling of falling down while asleep happens because, during sleep, muscles become very relaxed and enter into temporary paralysis. The brain misinterprets this as falling and sends signals to muscles to jerk the person upright which leads to a rocky awakening.

A shocking, falling sensation during sleep has been felt by many people. It feels like you have no control over your body, and you are just floating with no support ready to fall. Then there is a sudden jerk that wakes you up. Everyone would agree that the feeling is not at all pleasant.

These jerks are known as hypnic jerks and are sometimes accompanied by visual hallucinations. These sudden episodes occur when the muscles, especially in the legs, contract quite quickly and involuntarily. It feels almost like a twitch or spasm. Mankind is yet to fully understand the significance of these spams, but experts believe that there might be two evolutionary perspectives.

First, this sudden awakening allows us to monitor our environment before going into deep sleep. This might have been a compulsory “check-in” during early human times. Secondly, it helps to understand the stability of the body position. For example, if someone falls asleep in a compromising position where they might fall and hurt themselves, this sudden jerk would help to prevent that. (1, 2)

10 When a person blushes, the interior lining of their stomach also turns red. This is the doing of the sympathetic nervous system that causes increased blood flow throughout the body.

The human stomach is a marvelous creation. The mechanism is quite interesting. The stomach keeps digesting continuously throughout the day. When it gets empty, it starts making growling sounds. The sound originates from the digestive juices that are still in the process of trying to digest food without any food in the stomach.

Another interesting phenomenon in the stomach happens when a person blushes. During blushing, there occurs an increased blood flow throughout the body caused by the nervous system. Adrenaline production increases leading to a further increase in the blood flow by dilating blood vessels. As a result, all the blood vessels turn redder than average.

The same happens to the blood vessels lining the stomach walls. So, when you blush, your stomach blushes too! (1, 2)