Why Do We Turn White When Frightened?
We turn white when we are frightened because the blood in our cheeks is diverted to do a more urgent job. At the same time our heart begins to beat much faster, and we breathe more quickly. When we sit still, our hearts beat at about 70 or 80 times a minute, pumping the blood through our bodies. The blood carries nourishment from food, and oxygen from the air we breathe, both of which are vitally necessary for the body to function.
If we take violent exercise, our muscles need to work much harder and faster than when we are sitting or walking. They therefore need extra nourishment and oxygen. The nerves carry the message to that part of the brain called the hypothalamus, the centre of an automatic nervous system in control of internal bodily functions such as the pumping of the heart, breathing and digestion.
Impulses from the hypothalamus travel down the spinal cord and excite other nerve cells-“sympathetic” neurons-which end in the centre or medulla of the adrenal glands just above the kidneys. These glands release the hormone adrenalin into the blood stream which causes the heart to beat faster and more efficiently, dilates air passages in the lungs and the blood vessels that supply the muscles, and increases the concentration of energy giving glucose in the blood.
In fact, when we are frightened, exactly the same physical changes take place and our bodies are immediately and efficiently prepared for the violent exercise of flight or fight without any voluntary effort on our part.
Adrenaline has a variety of effects including enhancing perspiration (or diaphoresis, which prepares the body for the increase in temperature associated with fleeing/fighting), dilation of the pupils (which increases light sensitivity, but reduces acuity), dry mouth (gastric juices and saliva production decreases because blood flow to the digestive system is decreased), enhanced smell and hearing, and a cool, pale skin.
The cool and pale skin is caused by a reduced blood flow to the surface of the body, while blood flow to the arms, legs, shoulders, brain, eyes, ears and nose can be increased. Besides getting ready to run and fight, the body is preparing to think quickly and be aware of threats by hearing, seeing and smelling things better.
Pulling blood away from the skin also helps decrease bleeding from cuts and scrapes. Adrenaline stimulates alpha-adrenoreceptors in blood vessels, which causes the smooth muscles around the vessels to constrict.