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Chapter 3 The Muscular System 63
Cardiac muscle, also called myocardial (MIGH-
oh-KAR-dee-uhl) muscle, is found only in the
heart. Like smooth muscle, cardiac muscle is
unconsciously controlled. As cardiac muscle
involuntarily contracts, it pumps blood from the
heart into blood vessels.
You probably have heard the saying, “It takes more
muscles to frown than it does to smile.” Did you
know that you have more than 30 facial muscles
that produce a range of subtly different expressions
including happiness, sadness, surprise, anger, fear,
disgust, and astonishment?
Fascinating Fact
Muscle Tissue Properties
Muscle tissue has many unique properties. It is
the only tissue in the body that has the following
physiological characteristics:
• automaticity (AW-toh-muh-TIH-sih-tee)—the
ability of a muscle to contract without the involve-
ment of a nerve supply. Automaticity is a prop-
erty of visceral, smooth, and cardiac muscles.
• contractility (KAHN-trak-TIL-ih-tee)—the abil-
ity of a skeletal muscle to contract (shorten); for
example, the biceps muscle contracts when the
arm is fl exed.
Figure 3.1 Anterior and posterior views of the major muscles in the body.
Trapezius
Deltoid
Pectoralis major
Triceps brachii
Biceps brachii
Gluteus maximus
Gluteus
medius
Sartorius
Biceps femoris
Rectus femoris
Gastrocnemius
Achilles tendon
Abdominal
muscles
Latissimus dorsi
Frontalis
A. Anterior view B. Posterior view
Label
art