We all know the effects of the body’s chemical activator. Adrenaline (C₉H₁₃NO₃), also known as epinephrine, is a natural hormone. The fight or flight response requires extra supplies of blood and oxygen in the muscles. Fear causes the adrenal gland to pump large amounts of adrenaline into the bloodstream. It acts on organs such as the lungs, heart, uterus and alimentary tract, increasing heart and breathing rates in preparation for action.

It does this by binding to receptors on the cell surface of organs. This triggers a cascade of reactions inside the cells, and it is this cascade that causes the biological response.

Adrenaline is responsible for our hearts pounding and beating faster when we prepare to carry out physically or emotionally demanding activities. Our eyes dilate, we start to sweat and our mouths fill with saliva. However the hydrogen bonding groups in the molecule keep it from passing through the curtain of the blood-brain barrier, so that we can remain clear headed in times of danger.