Published: 4 November, 2004

Nervous System Makes us Blush

Why do your cheeks turn red when you get embarrassed? How come when we get nervous our heart feels like it's beating faster?

It might seem surprising to imagine the body controlled by the brain, and so sensitive to our feelings, but this is a fundamental brain function that prepares us for combat or escape from a potentially dangerous situation, animal, or person. There are four main functions of the brain: (1) to sense (think of the five senses), (2) to move muscles, (3) to think and feel, (4) to control things like breathing and heart rate that are vital for survival. Vital functions are mediated by the balance of activity in opposing brain systems, the sympathetic and parasympathetic nervous systems, that either stimulate or relax internal organs, respectively. Also called the 'fight-or-flight' and 'rest-and-digest' systems, the balance of activity in these systems is governed by emotions and environmental demands.

The sympathetic nervous system kicks into gear when we get nervous or embarrassed and elicits a response of the body that includes: a widening of the pupils, faster beating of the heart and more rapid breathing, the hair to stand-up, sweating, the release of the hormones adrenalin and noradrenalin into the circulation from the adrenal gland.

But do you turn beet red or white as a ghost? During extreme fear or anger, the blood vessels in the skin constrict due to the release of large amounts of adrenalin and noradrenalin, however slight to moderate sympathetic activation causes a dilation of the facial blood vessels due primarily to adrenalin. How a person's perception of embarrassment or fear can evoke a gradation in the sympathetic response is not well understood however, our sensation of our heart beating faster, feeling flushed, etc., is an important component of our sense of fear or embarrassment; individuals suffering from impaired sympathetic function often describe not 'feeling' emotions as intensely as they were able to before the injury.