Module 1

Module 1—The Nervous System

Lesson Summary

 

In this lesson you investigated the following focusing questions:

• How is the nervous system organized, and how do its 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 the autonomic nervous system. The autonomic nervous system is composed of two subdivisions—the parasympathetic and sympathetic systems.

 

The functional unit of the nervous system is the neuron. Neurons are bundled together to form nerves. The nervous system gathers information using sensory neurons or a sensory pathway. 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.

 

These pathways may sometimes be disrupted, causing communication to be interrupted. In Lesson 3 of this module, you will explore an example of a rapid form of communication called a reflex arc. In other lessons you will continue to explore the consequences when communication in these pathways is interrupted.

 

In multiple sclerosis, a special type of communication pathway is disrupted so that messages get lost or reach muscles very slowly or sporadically. In Alzheimer’s disease, brain neurons become dysfunctional and nerve messages cannot be transmitted within the brain.

 

Lesson Glossary

 

Consult the glossary in the textbook for other definitions that you may need to complete your work.

 

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: a 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, and 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: the 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: the 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, and flight subdivision

Biology 30 Learn EveryWare © 2009 Alberta Education