This chapter provided an overview of the nervous system. The nervous system is divided into two main parts: the central nervous system and the peripheral nervous system. The central nervous system consists of the brain and spinal cord. The peripheral nervous system consists of the autonomic nervous system and the somatic nervous system. The autonomic nervous system is further divided into the sympathetic nervous system (i.e., the fight or flight system) and the parasympathetic nervous system (i.e., the rest and digest system).
Neurons are the fundamental units of the nervous system. Neurons send electrical signals to other neurons via chemical messengers, known as neurotransmitters. The primary neurotransmitters of the nervous system are acetylcholine, norepinephrine, dopamine, serotonin, histamine, gamma-amino-butyric acid (GABA), and glutamate. Acetylcholine, epinephrine, and norepinephrine are the fundamental neurotransmitters within the autonomic nervous system. Drugs that stimulate acetylcholine (cholinergic medications) are known as parasympathomimetic. Drugs that block acetylcholine (anticholinergic) result in sympathetic stimulation. Drugs that stimulate the sympathetic nervous system are adrenergic receptor agonists or sympathomimetic.