Download 21.3 The Muscular System

21.3
The Muscular System
Lesson 21.3: True or False
Name
Class
Date
Write true if the statement is true or false if the statement is false.
1. Muscles are organs composed mainly of muscle cells.
2. Each muscle fiber is a very short, thin cell.
3. There are four types of muscle tissues in the human body.
4. Both skeletal and cardiac muscles appear striated, or striped.
5. Contractions of smooth muscle are voluntary.
6. Skeletal muscle is the most common type of muscle in the human body.
7. Cardiac muscle contains a great many mitochondria.
8. There are well over 600 skeletal muscles in the human body.
9. Each skeletal muscle consists of 125-skeletal muscle fibers.
10. Muscles can contract, actively extend, and lengthen.
11. In exercises such as weight lifting, skeletal muscle contracts against a resisting force.
12. Continued exercise is necessary to maintain bigger, stronger muscles.
13. Each muscle fiber contains hundreds of organelles called myofibrils.
14. The region between two Z lines is called a sarcomere.
15. Voluntary contractions of cardiac and smooth muscles are also controlled by nerves.
Lesson 21.3: Critical Reading
Date
Class
Name
Read these passages from the text and answer the questions that follow.
What Are Muscles?
Muscles are organs composed mainly of muscle cells, which are also called muscle fibers. Each muscle
fiber is a very long, thin cell that can do something no other cell can do. It can contract, or shorten. Muscle
contractions are responsible for virtually all the movements of the body, both inside and out. There are
three types of muscle tissues in the human body: cardiac, smooth, and skeletal muscle tissues. They are
shown and described below.
Skeletal muscle
Smooth muscle
Cardiac muscle
Types of Muscle Tissue. Both skeletal and cardiac muscles appear striated, or striped, because their cells
are arranged in bundles. Smooth muscles are not striated because their cells are arranged in sheets instead
of bundles. (From left to right, images courtesy of the Department of Histology at Jagiellonian University
Medical College, Polarlys, and Nathanael Reveal (Nathanael). All images under GNU-FDL 1.2.)
Smooth Muscle
Muscle tissue in the walls of internal organs such as the stomach and intestines is smooth muscle. When
smooth muscle contracts, it helps the organs carry out their,functions. For example, when smooth muscle
in the stomach contracts, it squeezes the food inside the stomach, which helps break the food into smaller
pieces. Contractions of smooth muscle are involuntary. This means they are not under conscious control.
Skeletal Muscle
Muscle tissue that is attached to bone is skeletal muscle. Whether you are blinking your eyes or running a
marathon, you are using skeletal muscle. Contractions of skeletal muscle are voluntary, or under conscious
control. Skeletal muscle is the most common type of muscle in the human body, so it is described in more
detail below.
Cardiac Muscle
Cardiac muscle is found only in the walls of the heart. When cardiac muscle contracts, the heart beats
and pumps blood. Cardiac muscle contains a great many mitochondria, which produce ATP for energy.
This helps the heart resist fatigue. Contractions of cardiac muscle are involuntary, like those of smooth
muscle.
Questions
1. Describe what a muscle fiber looks like and what it can do.
2. What are the three types of muscle tissues in the human body and where are they located?
3. Explain how cell arrangement causes a muscle to appear either striated or not striated.
4. For each type of muscle tissue, list whether it is voluntary or involuntary.
5. Why is it important for cardiac muscle to have many mitochondria?
Lesson 21.3: Multiple Choice
Name
Class
Date_
Circle the letter of the correct choice.
1. Smooth muscle is found in the
(a)
(b)
(c)
(d)
heart.
stomach.
upper leg.
middle ear.
2. Skeletal muscle fibers are wrapped in
(a)
(b)
(c)
(d)
fat.
bone.
connective tissue.
none of the above.
3. Skeletal muscles need a rich blood supply to provide them with
(a)
(b)
(c)
(d)
oxygen.
carbon dioxide.
water.
none of the above.
4. The biceps and triceps muscles are located in the
(a)
(b)
(c)
(d)
lower arm.
upper arm.
knee.
stomach.
5. Each myofibril is made up of how many types of protein filaments?
(a)
(b)
(c)
(d)
one
two
three
four
6. Actin filaments are anchored to structures called
(a)
(b)
(c)
(d)
W lines.
X lines.
Y lines.
Z lines.
7. Muscles need a stimulus from which of the following to "tell" them to contract?
(a)
(b)
(c)
(d)
a muscle cell
the skeleton
a nerve cell
none of the above
8. Two main proteins found in muscle are
(a)
(b)
(c)
(d)
smooth and skeletal.
tendons and ligaments.
actin and myosin.
myofibrils and fibers.
Lesson 21.3: Vocabulary I
Name
Class
Date
Match the vocabulary word with the proper definition.
Definitions
1. muscle tissue that is attached to bone
2. long, thin muscle cell that has the ability to contract, or shorten
3. theory that explains muscle contraction by the sliding of myosin filaments over actin filaments
within muscle fibers
4. tough connective tissue that attaches skeletal muscle to bones of the skeleton
5. human body system that includes all the muscles of the body
6. organs composed mainly of muscle cells
7. the region between two Z lines
8. involuntary, nonstriated muscle that is found in the walls of internal organs such as the stomach
9. organelles contained within each muscle fiber
10. involuntary, striated muscle found only in the walls of the heart
11. tiny structures within the myosin filaments, that can attach to actin filaments
Terms
a. cardiac muscle
b. cross bridges
c. muscle fiber
d. muscles
e. muscular system
f. myofibril
g. sarcomere
h. skeletal muscle
i. sliding filament theory
j. smooth muscle
k. tendon
Lesson 21.3: Vocabulary II
Name
Class
Date
Fill in the blank with the appropriate term.
1. Both skeletal and
muscles appear striated.
2. Muscle tissue that is attached to
is skeletal muscle.
3. Contractions of skeletal muscle are voluntary, or under
control
4. Cardiac muscle contains a great many mitochondria, which produce
energy.
for
5. Skeletal muscles need a rich blood supply to provide them with
oxygen and to carry away their wastes.
and
6. Many skeletal muscles are attached to the ends of bones that meet at a
7. Muscles can only contract and cannot actively
8. To move bones in opposite directions, pairs of
.
.
must work in opposition.
9. In exercises such as weight lifting, skeletal muscle contracts against a
force.
10. If you don't use a muscle, it will get smaller and weaker—so use it or
it.
11. Muscle contraction occurs when muscle fibers get
12. Within a sarcomere, myosin
filaments
.
the actin filaments.