Building on our discussion of the skeletal system in

Chapter 5, in this chapter we consider the three kinds of

muscle that move the body and its parts. Our main focus

is skeletal muscle, which moves bones.

Chapter 3 introduced the proteins actin and myosin, and

here you will learn how they work together as skeletal

muscles contract (3.9). Our discussion also will draw on

your knowledge of how ATP fuels cell activities (3.8) and

how active transport moves substances into and out of

cells (3.11).

Links to EarLiEr ConCEpts

Even if you are not as buff as the athlete in this photograph,

you probably know that your ability to move your body depends on

properly functioning muscles. The testing gear this fellow is wearing

as he works out on a treadmill provides information on the amount

of oxygen his muscular heart is pumping to the equally hard-working

muscles of his limbs, not to mention muscles involving in breathing

and other body functions. In this chapter we begin with the natural

roles of the body’s three types of muscle tissue. Then we’ll look at

the structure and functioning of skeletal muscles—the muscles that

partner with the skeleton to bring about body movements.

thE musCuLar systEm

6

103

kEy ConCEpts

Types of Muscle Tissue

The three types of body muscle are

skeletal muscle, smooth muscle, and

cardiac muscle. Muscle cells produce

force by contracting. S e c t i o n 6 .1

Top Three: © Cengage Learning; Bottom:© Maxisport/Shutterstock.com

What Skeletal Muscles Do

Skeletal muscles pull on bones to

move body parts. They are arranged

as pairs or groups. Often, the action

of one muscle opposes or reverses

the action of another. Section 6.2

How Muscles Work

In a muscle cell, the action of units

called sarcomeres is the basis for

muscle contraction, which is con-

trolled by motor neurons. Sections

6.3–6.6, 6.8

homeostasis preview

Muscle contractions move body parts and substances such as

blood and food to be digested. They also produce much of the

body’s heat.

Disorders of the Muscular

System Section 6.7

connecTionS:

Muscles and the Muscular

System in Homeostasis

Section 6.9

© iStockphoto.com/technotr

Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).