Lesson 2 | The Muscular System



Name Date Class

LESSON 2

The Muscular System

Directions: Circle the term in parentheses that correctly completes each sentence.

1. Muscles do their work by (contracting/expanding).

2. Muscles that are attached to bones give us movement and (stability/energy).

3. The longest muscle in the body extends from the knee to the (shoulder/hip).

4. Shivering is a way in which the muscles maintain the body’s

(chemical balance/internal temperature).

5. The three types of muscles are skeletal, smooth, and (cardiac/abdominal).

6. Skeletal muscles are also called (voluntary/involuntary) muscles.

7. Smooth muscles are smoother and (longer/shorter) than skeletal muscles.

8. The discs at the ends of heart muscle cells coordinate the heart’s

(pumping action/cell replacement).

9. The energy that muscles need to function comes from (food/sunlight).

10. Without exercise, muscles get smaller and (flatter/weaker).

30 Structure and Movement

Name Date Class

LESSON 2

Word-Meaning Activity

Matching

Directions: On the line before each definition, write the letter of the term that matches it correctly.

1. We are strong tissues made of cells that contract

and relax. We give your body the ability to move.

2. We are also called skeletal muscles. We are

muscles that you can consciously control.

3. We are muscles that move even while you are

asleep.

4. We are muscles that attach to bone. We help you

kick a ball and raise your arm.

5. We are muscles that make up your blood vessels

and your stomach. We are at work even when

you are not aware of it.

6. We are muscles that make up your heart. We are

made of cells that work together to contract at

nearly the same time.

A. cardiac muscles

B. involuntary muscles

C. muscles

D. smooth muscles

E. skeletal muscles

F. voluntary muscles

Structure and Movement 33

Name Date Class

LESSON 2

The Muscular System

Key Concept How do the types of muscle differ?

Directions: Circle the term or phrase that correctly completes each sentence.

skeletal and cardiac.

1. The two kinds of involuntary muscles are smooth and skeletal.

smooth and cardiac.

only push on bones.

2. Skeletal muscles can only pull on bones.

push and pull on bones.

alone.

3. Skeletal muscles operate in pairs.

in triplets.

heart.

4. Cardiac muscles are located only in the blood vessels.

abdomen.

knobs.

5. Cardiac muscle cells have branches ending in points.

discs.

6. Compared with skeletal muscle cells, smooth muscle

cells are

shorter and smoother.

longer and smoother.

wider and smoother.

Structure and Movement 37

Name Date Class

LESSON 2

The Muscular System

When a person dies, the respiratory and

circulatory systems stop delivering oxygen

to the muscles. Muscles use oxygen to

produce ATP, an energy molecule that helps

them relax after contracting. Without ATP,

the muscles stiffen. About 10 to 12 hours

after death, the muscles and joints are

locked into place. This condition is called

rigor mortis.

Rigor Mortis

The term rigor mortis comes from the

Latin words rigor, meaning “stiff,” and

mort, meaning “death.” Rigor mortis

usually affects the facial muscles first,

sometimes within minutes after death.

It then moves to other parts of the upper

body and finally to the lower body. Several

factors affect rates of rigor mortis, including

temperature. Cold temperatures slow

rates of rigor mortis. In contrast, warm

temperatures increase rates of rigor mortis.

A person who exercises shortly before

death will have a warm body temperature,

increasing the rate of rigor mortis.

Fat distribution and age also affect how

quickly rigor mortis sets in.

Rigor mortis usually lasts about one to

two days. A body found outside during the

winter, however, might be locked in rigor

mortis for days. During this period, tissues

in the body begin to decay. This causes

the muscles to relax. The muscles generally

relax in the same order in which they

stiffened—that is, relaxation begins in the

face first and then moves to other parts of

the body.

Forensics

Rigor mortis can provide useful

information in forensic studies. Forensics

is the science of gathering and analyzing

evidence for legal purposes. This work

sometimes involves crime-scene

investigations. Rigor mortis can help

forensic scientists determine the time of

death. Because a body tends to stiffen in

the position it held at the moment of

death, rigor mortis can also help scientists

determine whether a body was moved.

Applying Critical-Thinking Skills

Directions: Answer each question or respond to each statement.

1. Evaluate The upper body of a corpse is stiff, but the lower body is relaxed. When

might death have occurred? Explain your answer.

2. Infer On Friday, police find the body of a person who they know died on Tuesday. The

body exhibits full rigor mortis. What can you infer about the conditions in which the

body was found?

Structure and Movement 39

Name Date Class

LESSON 2

The Muscular System

Multiple Choice

Directions: On the line before each question, write the letter of the correct answer.

1. Which is a function of the muscular system?

A. protects internal organs

B. produces red blood cells

C. creates immovable joints

2. Which system does the muscular system work with when it moves food

through the body?

A. skeletal system

B. immune system

C. digestive system

Matching

Directions: On the line before each definition, write the letter of the term that matches it correctly. Each term is

used only once.

Matching Set 1

3. muscles located in internal organs

4. muscles located only in the heart

5. muscles attached to bones

A. cardiac

B. skeletal

C. smooth

Matching Set 2

6. smooth muscles

7. skeletal muscles

8. the way muscles raise body temperature

9. attach muscles to bones

D. shivering

E. voluntary

F. tendons

G. involuntary

Structure and Movement 43

Name Date Class

LESSON 2

The Muscular System

Key Concept How do the types of muscle differ?

There are two main types of muscles—voluntary and involuntary.

Directions: On the lines, write a V next to each function that is controlled by voluntary muscles. Write an I next

to each function that is controlled by involuntary muscles.

1. smiling

2. digestion

3. walking

4. heartbeat

5. jumping

6. talking

Directions: Answer each question on the lines provided

7. What are voluntary muscles connected to?

8. For that reason, what are these muscles usually called?

9. These muscles are made of long, thin cells that give the muscles a striped appearance.

What are these stripes called?

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Content Practice A

Language Arts Support

Key Concept Builder

Enrichment

Lesson Quiz A

Key Concept Builder

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