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3.4 Putting It All Together: The Nervous System and the Endocrine System
LEARNING OBJECTIVES
- Summarize the primary functions of the CNS and of the subsystems of the PNS.
- Explain how the electrical components of the nervous system and the chemical components of the endocrine system
work together to influence behavior.
Now that we have considered how individual neurons operate and the roles of the different brain
areas, it is time to ask how the body manages to “put it all together.” How do the complex
activities in the various parts of the brain, the simple all-or-nothing firings of billions of
interconnected neurons, and the various chemical systems within the body, work together to
allow the body to respond to the social environment and engage in everyday behaviors? In this
section we will see that the complexities of human behavior are accomplished through the joint
actions of electrical and chemical processes in the nervous system and the endocrine system.
Electrical Control of Behavior: The Nervous System
The nervous system (see Figure 3.17 "The Functional Divisions of the Nervous System"), the
electrical information highway of the body, is made up ofnerves—bundles of interconnected
neurons that fire in synchrony to carry messages. The central nervous system (CNS), made up of
the brain and spinal cord, is the major controller of the body’s functions, charged with
interpreting sensory information and responding to it with its own directives. The CNS interprets
information coming in from the senses, formulates an appropriate reaction, and sends responses
to the appropriate system to respond accordingly. Everything that we see, hear, smell, touch, and
taste is conveyed to us from our sensory organs as neural impulses, and each of the commands
that the brain sends to the body, both consciously and unconsciously, travels through this system
as well.