The adrenergic system or adrenergic nervous system (ANS) is the group of nerves and organs that are sensitive to the neurotransmitters adrenaline and norepinephrine. The ANS is considered to be one of the main neurohormonal systems of the body and is responsible for regulating cardiovascular functions and smooth muscle tone.
It is composed of the sympathetic nervous system (SNS), the parasympathetic nervous system (PNS) and the enteric nervous system (ENS). These systems normally work together smoothly but when overstimulated by disease processes (neurological conditions such as rabies) or drug overdose can trigger what is known as an adrenergic storm that releases a massive amount of neurotransmitters simultaneously that can prove fatal to those with previous cardiac problems.