Module 1 The Nervous System

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Lesson Summary

In this lesson you investigated the following focusing questions:

• How is the nervous system organized and how do these parts communicate with each other?

• What interrupts the normal communication mechanisms of the sympathetic and parasympathetic parts of the nervous system?

To answer these questions, you explored the human nervous system as a complex communication system organized into the central nervous system and the peripheral nervous system. These systems work together to maintain homeostasis.

The motor neurons of the peripheral nervous system take information from the brain and spinal cord to the somatic nervous system and/or the autonomic nervous system. The autonomic nervous system is composed of two subdivisions (parasympathetic and sympathetic systems).

The functional unit of the nervous system is the neuron. Neurons bundle together to form nerves. The nervous system gathers information using sensory neurons or a sensory pathway. And the nervous system integrates information using interneurons like those found in the brain and spinal cord. Instructions are then transmitted by motor neurons or motor pathways to muscles and glands. These muscles and glands are called effectors because they initiate a response.

Lesson Glossary

autonomic nervous system (ANS): a division of the peripheral nervous system that conducts nerve impulses to cardiac and smooth muscles, as well as to glands; may also be called the involuntary motor system

central nervous system (CNS): the part of the nervous system that includes the brain and spinal cord

homeostasis: a state of body equilibrium or a stable internal environment of the body

nerve: message pathway of the nervous system; made up of many neurons grouped into bundles and surrounded by protective tissue; there are 12 pairs of cranial nerves that insert into the brain and 31 pairs of spinal nerves that emanate from the spinal cord
nervous system: an elaborate communication system that receives input, processes, integrates, stores information, and triggers muscle contraction or glandular secretion

neuron: the basic functional cell of the nervous system that is specialized to generate and transmit nerve impulses (messages)

parasympathetic nervous system: division of the autonomic nervous system that oversees digestion, elimination and glandular function; often works opposite the sympathetic nervous system to bring the body back to normal
peripheral nervous system (PNS): the portion of the nervous system consisting of nerves and ganglia (collections of nerve cell bodies) that are outside the brain and spinal cord
somatic nervous system (SNS): a division of the peripheral nervous system that conducts nerve messages to the skeletal muscles; may sometimes be called the voluntary nervous system
sympathetic nervous system: division of the autonomic nervous system that activates the body to cope with some stressor, such as danger, excitement, or fear; sometimes referred to as the fight, fright, flight subdivision