Nerve Cells "Talk" to Each Other
LEARNING OBJECTIVES
1.
List
the structures and basic functions of the
nervous system.
2.
Identify
the cells of the nervous system and
their functions.
3.
Outline
the events in an action potential.
4.
Describe
the process of synaptic transmission.
onsider a computer. It has a central process-
ing unit (microchip) with memory, ways to
receive information (keyboard, mouse, disk
drives, ports, modem), and ways to send in-
formation (disk drives, ports, modem). It receives infor-
mation, processes it, and sends it out. Your nervous system
does basically the same thing.
The Nervous System Has Sensory,
Motor, and Integrative Functions
Instead of being made of silicon, wires, and circuit boards,
your nervous system consists of billions of nerve cells
called
neurons
and supporting cells called
neuroglia
(noo-ROG-le- a) or glial cells. Cells of the nervous system ei-
ther lie within the
central nervous system (CNS)
, which in-
cludes the brain and spinal cord (see Figure 7.1), or outside
the CNS in the
peripheral nervous system (PNS)
, which in-
cludes the cranial and spinal nerves as well as cells in the
peripheral nervous
central nervous
system (PNS)
The portion
system (CNS)
The
of the nervous system that
portion of the nervous
consists of nervous tissue
system that is com-
structures that lie outside the
posed of the brain and
brain and spinal cord.
spinal cord.
S tructural o verview o f th e nervo u s sy stem • Figure 7.1
The nervous system is divided into two parts. The peripheral nervous system (PNS) senses
changes in the environment, sends information to the central nervous system (CNS), and
receives information from the CNS. The central nervous system processes information and
makes decisions.
Central Nervous System (CNS):
Brain
(100 billion neurons) is
involved in information
processing.
Spinal cord (100 million
neurons) transmits information to
and from the brain and does
some information processing
(reflexes).
192 CHAPTER 7
The Nervous System
TT
Peripheral Nervous
System (PNS):
Cranial
nerves provide
sensory and motor
functions to the face and
several vital organs (heart,
respiratory muscles).
Spinal nerves
provide
sensory and motor
functions to specific
regions of the body.
Enteric plexuses are
networks of neurons in the
walls of the digestive
organs that regulate the
digestive system.
Sensory receptors
are
endings of sensory
neurons or specialized
cells that monitor changes
in the internal and/or
external environment.
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