319
10
The Muscular System
Actions and Interactions of Skeletal
Muscles
(pp.
319–320)
Naming Skeletal Muscles
(pp. 320–322)
Muscle Mechanics: Importance of Fascicle
Arrangement and Leverage
(pp. 322–324)
Arrangement of Fascicles (pp. 322–323)
Lever Systems: Bone-Muscle
Relationships (pp. 323–324)
Major Skeletal Muscles of the Body
(pp. 324–382)
T
he human body enjoys an incredibly wide range of movements.
Te
gentle blinking of your eye, standing on tiptoe, and wielding a sledgehammer are
just a sample of the actions made possible by your muscular system.
Muscle tissue includes all contractile tissues (skeletal, cardiac, and smooth muscle),
but when we study the muscular system,
skeletal muscles
take center stage. Tis chap-
ter focuses on these muscular “machines” that enable us to perform so many different
activities. However, before describing the individual muscles in detail, we will consider
Te manner in which muscles “play” with or against each other to bring about
movement
Te criteria used for naming muscles
Te principles of leverage
Actions and Interactions of Skeletal Muscles
Describe the functions of prime movers, antagonists, synergists, and fixators.
Explain how a muscle’s position relative to a joint affects its action.
Te arrangement of body muscles permits them to work either together or in opposi-
tion to produce a wide variety of movements. As you eat, for example, you alternately
raise your fork to your lips and lower it to your plate, and both sets of actions are ac-
complished by your arm and hand muscles. But muscles can only
pull
; they never
push
.
Generally as a muscle shortens, its
insertion
(attachment on the movable bone) moves
toward its
origin
(its fixed or immovable point of attachment). Whatever one muscle or
muscle group can do, another muscle or group of muscles can “undo.”
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