Functional overview o f th e nervo u s sy stem • Figure 7.2
walls of the digestive organs and the sensory organs. Not
to be confused with neurons, nerves are bundles of nerve
fibers in the peripheral nervous system. The PNS is subdi-
vided further according to functions of groups of sensory
and motor neurons ( •
The afferent (sensory) nervous system consists of
a variety of nerve receptors and their associated nerve
Som atosensory receptors
are associated with the muscles,
joints, and skin.
S p ec ia l sense receptors
are found in the ear, eye, nose,
A u to n o m ic sensory receptors
are found in the internal
The efferent (motor) nervous system is composed
of motor nerve fibers that regulate the activities of
muscle and glandular tissues throughout the body.
This system can be subdivided into three sections:
• The somatic nervous system (SNS) deals with
skeletal muscle actions that move the body around
• The autonomic nervous system (ANS) regulates
involuntary functions (such as heart rate, breathing
muscle, smooth muscle, and glandular tissue. This
system consists of two divisions, sympathetic and
parasympathetic, which have opposite effects.
• The enteric nervous system (ENS) is an intricate
network of nerve fibers within the digestive organs
digestive system and interacts with the ANS.
Like a computer, your nervous system accomplishes
the following functions:
Sensory fu n c tio n
in p u t).
peripheral nervous system
sense changes in
internal and external environments, such as changes in
blood pressure, injuries, touch, and pain, and send this
information to the central nervous system (CNS).
In teg ra tiv e fu n c tio n (in fo rm a tionprocessing).
Neurons in the
CNS analyze sensory information and make decisions
require perception (or mental awareness) and higher-
M o to r fu n c tio n
o u tp u t).
information and making decisions, CNS neurons send
commands to muscular or glandular effectors that carry
out responses such as muscle contraction/relaxation or
increased/decreased secretion of substances such as oil
Let’s take a closer look at the cells that make up the
Nerve Cells "Talk" to Each Other 193