As a rule, the human body operates in two modes - calm and excited.
The first one operates when we, for example, sit, lie down or read – at such moments the nervous system is calm, since the listed types of activities are predictable and everything goes as usual.
If you are running, that is, in an excited state, some systems of the body require more.
As a result, the blood distribution mechanism “takes” it from the skin and gives it to certain muscles and organs.
The same thing happens if a person suddenly encounters danger: his body abruptly changes from a calm mode to an excited one, which, as mentioned above, triggers the blood distribution mechanism.
The parasympathetic nervous system ensures the redistribution of blood flow in favor of the external parts of the body and temporarily reduces the blood supply to those organs and systems that are not involved in the fight against a specific threat.
So when you feel fear, not only do you turn pale, but you also experience dry mouth because the fight or flight response slows down digestion, which dries out your saliva.
This "fight or flight" response is also associated not only with pale skin and dry mouth, but also with the release of adrenaline, which is expressed in increased sweating, dilated pupils and a heightened sense of smell.
