Chapter 7: The Nervous System

Introduction - Page 222

The nervous system

• Master controlling and communicating system of the body

• Every thought, action, and emotion reflects its activity

• Signaling device: – Electrical impulses (rapid, specific & cause

immediate response)

Three overlapping functions

• 1. Sensory input– Millions of sensory receptors to monitor changes

occurring inside & outside the body – Changes are called stimuli

• 2. Integration– Processing and interpretation of sensory input– Makes decisions about what should be done

• 3. Motor output – Effects a response– Activates muscles or glands (effectors)

How do these functions work together?

• You are driving and see a red light ahead. How do these three functions work together? – 1.? Give me an example sensory input?– 2.? Give me an example integration?– 3.? Give me an example motor output?

Organization of the nervous system

• Very complex

• We can divide it in terms of structures and functions

Structural Classification

• The nervous system has two subdivisions:– Central nervous system (CNS)

• Brain and spinal cord• Integrating and command centers of the nervous system• Interpret incoming sensory information and issue instructions

based on past experience and current conditions

– Peripheral nervous system (PNS)• Nerves that extend from the brain and spinal cord • Spinal nerves – carry impulses to and from the spinal cord• Cranial nerves – carry impulses to and from the brain • Think of communication lines

Functional Classification

• Concerned only with the PNS

• Two subdivisions: – 1. Sensory (afferent) division

• Nerve fibers that convey impulses to the CNS from sensory receptors

• Sensory fibers delivering impulses from the skin, skeletal muscles, and joints are called somatic fibers

• Sensory fibers … form visceral organs are called visceral sensory fibers

Functional Classification (cont.)

• The second subdivision: – 2. Motor (efferent) division

• Carries impulses from the CNS to effector organs, muscles, and glands

• Activate muscles and glands (that is, they effect or bring about a motor response)

The motor division has two subdivisions

• 1. The somatic nervous system– Allows us to consciously, or voluntarily, control our

skeletal muscles – Sometimes called the voluntary nervous system

• 2. The automatic nervous system– Regulates events that are automatic, or involuntary

(cardiac and smooth muscles)– Sometimes called the involuntary nervous system– Two parts: sympathetic and parasympathetic

• We’ll talk about this later

Confused? Take a look at the graphic organizer on page 224

• Copy this graphic organizer in your notes.

• Homework: read pages 222-228 AGAIN!!!

• Bring book this week

• Expect a quiz on pages 222-228 Friday