ABSTRACT
The autonomic nervous system maintains many of our life-supporting functions. The synapse, whether it is between nerve, muscle, or gland cells, is a central target for drug design. The parasympathetic fibers use acetylcholine as the neurotransmitter and are called cholinergic. The sympathetic fibers use norepinephrine at their terminal synapses and are called adrenergic. Sympathetic fibers also innervate the adrenal medulla, causing the release of adrenaline (mostly epinephrine). Different adrenergic receptor subtypes show tissue-specific distribution and responses. Stimulation of the adrenergic system is part of the fight or flight response and is related to how we respond to stressful situations. The HPA axis is also important in this response, as the potent corticosteroid released from the adrenal cortex also primes many tissues for the survival response. Regular exercise may replace the normal physical activity of our ancestors, which allowed them to cope with challenges to their survival. Sleep is an essential component of good health, as time is needed for the body to repair from the previous day and prepare for the next.
