Algonquin College
7.1 - Nervous System Functions and Organization
Introduction

The nervous system controls body functions and homeostasis. Cells of the nervous system can sense stimuli from the environment and respond by creating an amazing variety of thoughts, emotions, actions and physiological responses in conjunction with the hormone-producing endocrine system. The nervous system specializes in split-second responses to stimuli, whereas the hormones released by the endocrine system are slower to take effect and are typically more long-lasting.

The nervous system has three main functions that work in tandem to control the body:
  1. Sensory input. This is the gathering and sorting of sensory information; information about stimuli both inside the organism and in the external environment.
  2. Integration of sensory information. This is the processing and interpretation of sensory information, and the process of making decisions about how the body will respond to this information.
  3. Motor output is the response carried out by the body. Muscles or glands are the effectors that will carry out the response.
Organization of the Nervous System

The nervous system consists of the brain, spinal cord and nerves, which are organized into structural and functional divisions and classifications.

Structural Classifications

The nervous system is divided into two main subdivisions: The central nervous system (CNS) and peripheral nervous system (PNS) The central nervous system consists of the brain and spinal cord, both contained within the dorsal cavity. The brain and spinal cord contain the integration centers of the nervous system and are responsible for interpretation of sensory information and decision-making.

The peripheral nervous system consists any nervous system structures that are not contained in the CNS. The cranial and spinal nerves carry sensory information and motor output information to and from the integration centers in the brain and spinal cord, respectively.

Functional Classifications

The peripheral nervous system is divided into functional divisions: The sensory (afferent) division and the motor (efferent) division, which consists of two systems of efferent nerves (the somatic and autonomic systems).

The sensory division of the PNS consists of nerves that send sensory information from sensory receptors to integration centers for processing. The afferent spinal nerves and afferent cranial nerves make up the sensory division of the PNS.

The motor division of the PNS consists of nerves that deliver motor output information from integration centers to effector organs to carry out behavioral and physiological responses. The efferent spinal nerves control the somatic system of motor output, which is responsible for voluntary responses. The efferent cranial nerves control the autonomic system of motor output, which is responsible for involuntary responses. The autonomic system has two divisions: The sympathetic and parasympathetic divisions, which work against one another to produce a variety of involuntary responses under different conditions.