254
254
Colorized scanning
electron micrograph
(SEM) of freeze-
fractured muscle fi
bers.
S
ECT ION
A
Skeletal Muscle
Structure
Molecular Mechanisms of Skeletal
Muscle Contraction
Sliding-Filament Mechanism
Roles of Troponin, Tropomyosin, and
Calcium in Contraction
Excitation-Contraction Coupling
Membrane Excitation: The
Neuromuscular Junction
Mechanics of Single-Fiber Contraction
Twitch Contractions
Load-Velocity Relation
Frequency-Tension Relation
Length-Tension Relation
Skeletal Muscle Energy Metabolism
Muscle Fatigue
Types of Skeletal Muscle Fibers
Whole-Muscle Contraction
Control of Muscle Tension
Control of Shortening Velocity
Muscle Adaptation to Exercise
Lever Action of Muscles and Bones
Additional Clinical Examples
Muscle Cramps
Hypocalcemic Tetany
Muscular Dystrophy
Myasthenia Gravis
S
ECT ION
B
Smooth and Cardiac Muscle
Structure of Smooth Muscle
Smooth Muscle Contraction and Its
Control
Cross-Bridge Activation
Sources of Cytosolic Calcium
Membrane Activation
Types of Smooth Muscle
Cardiac Muscle
Cellular Structure of Cardiac Muscle
Excitation-Contraction Coupling in
Cardiac Muscle
chapter
9
Muscle
t
he ability to use chemical energy
to produce force and movement
is present to a limited extent in
most cells, but in muscle cells it has
become dominant. Muscles generate
force and movements used to regulate
the internal environment, and they
also produce movements in the
external environment. In humans, the
ability to communicate, whether by
speech, writing, or artistic expression,
also depends on muscle contractions.
Indeed, it is only by controlling
muscle activity that the human mind
ultimately expresses itself.
Three types of muscle tissue can be
identifi ed on the basis of structure,
contractile properties, and control
mechanisms—skeletal muscle, smooth
muscle, and cardiac muscle. Most
skeletal muscle, as the name implies, is
attached to bone, and its contraction is
responsible for supporting and moving
the skeleton. The contraction of
skeletal muscle is initiated by impulses
in the neurons to the muscle and is
usually under voluntary control.
Sheets of smooth muscle surround
various hollow organs and tubes,
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