Skip to ContentGo to accessibility pageKeyboard shortcuts menu
OpenStax Logo

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.


This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's permission.

Want to cite, share, or modify this book? This book uses the Creative Commons Attribution License and you must attribute OpenStax.

Attribution information
  • If you are redistributing all or part of this book in a print format, then you must include on every physical page the following attribution:
    Access for free at
  • If you are redistributing all or part of this book in a digital format, then you must include on every digital page view the following attribution:
    Access for free at
Citation information

© May 15, 2024 OpenStax. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution License . The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.