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Lesson
6.1
Overview of thethe Overview of
Nervous SystemSystem Nervous
Our nervous system is amazing in its ability
to simultaneously direct a whole host of different
functions. The nervous system not only controls
voluntary movement by activating skeletal muscle,
but it also directs the involuntary functions of
smooth muscle in internal organs and cardiac
muscle in the heart. By automatically controlling
the functions of smooth muscle and cardiac muscle,
the nervous system ensures that these life functions
are able to occur without conscious thought.
At the same time that your heart is beating
and your last meal is making its way through
your digestive tract, you may be talking to
a friend, walking to a class, or even reading
this book. Our senses—the ability to see, hear,
smell, taste, feel pressure, and feel pain—are
all dependent on sensory electrical input from
specialized receptors.
For the purpose of discussion, the nervous
system is organized into structural and
functional subdivisions. This organization makes
it easier to learn about the activities directed by
the various parts of the nervous system, and how
these parts interact.
Organization of the
Nervous System
There are two major divisions of the human
body’s nervous system: the central nervous
system and the peripheral nervous system.
There are further subdivisions of the peripheral
nervous system. Figure 6.1 illustrates these major
divisions and subdivisions.
First, let’s look at the organization of the
nervous system. We will examine the structure and
function of the two major divisions of the nervous
system in greater detail later in the chapter.
Before You Read
Try to answer the following questions before you read
this lesson.
Why are some body functions under involuntary
control?
Why is the myelin sheath around nerve axons so
important?
Lesson Objectives
1. Differentiate between the central nervous
system and peripheral nervous system, and
explain the function of each.
2. Explain the differences between afferent and
efferent nerves.
3. Describe the functions of the somatic and
autonomic branches of the nervous system.
4. Identify the general role of the glial cells.
5. Describe the anatomical structure of a
typical neuron.
Key Terms
afferent nerves
autonomic nervous
system
cell body
central nervous system
(CNS)
dendrites
efferent nerves
myelin sheath
neurilemma
neuroglia
nodes of Ranvier
peripheral nervous
system (PNS)
somatic nervous system
synapse
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