Chapter 7: The Nervous System: Structure and Control of Movement

OBJECTIVES

By studying this chapter, you should be able to do the following:

1. Discuss the general organization of the nervous system.

2. Describe the structure and function of a nerve.

3. Draw and label the pathways involved in a withdrawal reflex.

4. Define depolarization, action potential, and repolarization.

5. Discuss the role of position receptors in the control of movement.

6. Describe the role of the vestibular apparatus in maintaining equilibrium.

7. Discuss the areas of the brain involved in voluntary control of movement.

8. Describe the structure and function of the autonomic nervous system.

OUTLINE

• General Nervous System Functions 141

• Organization of the Nervous System 141

  • Structure of the Neuron 142

  • Electrical Activity in Neurons 142

• Sensory Information and Reflexes 149

  • Joint Proprioceptors 150

  • Muscle Proprioceptors 150

• Muscle Chemoreceptors 153

• Somatic Motor Function and Motor Neurons 153

• Vestibular Apparatus and Equilibrium 155

• Motor Control Functions of the Brain 156

  • Cerebrum 156

  • Cerebellum 157

  • Brain Stem 157

• Motor Functions of the Spinal Cord 159

• Control of Motor Functions 159

• Autonomic Nervous System 161

• Exercise Enhances Brain Health 162

KEY TERMS

action potential

afferent fibers

autonomic nervous system

axon

brain stem

cell body

central nervous system (CNS)

cerebellum

cerebrum

conductivity

dendrites

efferent fibers

excitatory postsynaptic potentials (EPSPs)

Golgi tendon organs (GTOs)

homeostasis

inhibitory postsynaptic potential (IPSP)

irritability

kinesthesia

motor cortex

motor neuron

motor unit

muscle spindle

neurons

neurotransmitter

parasympathetic nervous system

peripheral nervous system (PNS)

proprioceptors

reciprocal inhibition

resting membrane potential

Schwann cells

size principle

spatial summation

sympathetic nervous system

synapses

temporal summation

vestibular apparatus

INTRODUCTION

The nervous system provides the body with a rapid means of internal communication that allows us to move about, talk, and coordinate the activity of billions of cells. Thus, neural activity is critically important in the body’s ability to maintain homeostasis. This chapter will provide an overview of the nervous system, with emphasis on neural control of voluntary movement. We will begin with a discussion of the general function of the nervous system.

GENERAL NERVOUS SYSTEM FUNCTIONS

The nervous system is the body’s means of perceiving and responding to events in the internal and external environments. Receptors capable of sensing touch, pain, temperature changes, ...