The Nervous System

This lesson introduces the anatomy of the nervous system, including its functions and divisions. It also explores the parts of neuron, neural conduction, and synaptic transmission.

What Is the Nervous System?


From perceptions to daily experiences, the nervous system controls many aspects of the human body. This system coordinates several activities in the body. It governs people’s consciousness, their personalities, how they learn, and their ability to memorize. Working with the endocrine system, the nervous system regulates and maintains homeostasis.

The following flow chart summarizes the divisions of the nervous system.

The nervous system is anatomically divided into two parts:

  1. Central nervous system (CNS): The central nervous system is comprised of the brain and spinal cord. It is where information processing and control occurs.
  2. Peripheral nervous system (PNS): The peripheral nervous system is comprised of the nerves associated with the CNS. It connects all nerves of the body to the CNS. There are two types of fibers in the PNS: (a) afferent fibers that transmit impulses from organs and tissues of the body to the CNS; and (b) efferent fibers that transmit impulses from the CNS to the organs and tissues of the body.

The PNS is further divided into the somatic and autonomic nervous systems. The somatic nervous system primarily controls voluntary activities such as walking and riding a bicycle. Thus, this system sends information to the CNS and motor nerve fibers that are attached to skeletal muscle. The autonomic nervous system is responsible for activities that are non-voluntary and under unconscious control. Because this system controls glands and the smooth muscles of internal organs, it governs activities ranging from heart rate to breathing and digestion. The autonomic nervous system is further divided into the following:

  • Sympathetic nervous system: The sympathetic nervous system focuses on emergency situations by preparing the body for fight or flight.
  • Parasympathetic nervous system: The parasympathetic nervous system controls involuntarily processes unrelated to emergencies. This system deals with “rest or digest” activities.

Based on the activities of the nervous system, this system can be functionally divided into three parts:


Test Tip

The first letter in the parasympathetic and sympathetic nervous system can be used to tell them apart:
Sympathetic = stress 
Parasympathetic = peace


  1. Sensory: Information is gathered (both internally and externally) and carried to the CNS. The senses gather the information that the sensory nervous system transmits.
  2. Integrative: The integrative nervous system is where the CNS process and interprets information received from the sensory nerves.
  3. Motor: Motor nerves convey information that is processed by the CNS to muscles and glands.
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