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Lesson Overview
32.2 The Muscular System
Skeletal Muscle
Cardiac Muscle
Smooth Muscle
- Striations
-Controlled by nervous
system.
- Cells are large with many
nuclei.
- Similar to skeletal muscle
in striated shape and
similar to smooth muscle
because is not under
control of central nervous
system.
-Spindle-shaped cells with
single nucleus.
-Function without direct
stimulation by nervous
system
Attached to the bones
Found only in the heart
Walls of stomach, blood
vessels, and digestive
system
Lesson Overview
The Muscular System
Muscle Contraction
During a muscle contraction, myosin filaments form cross-bridges with
actin filaments. The cross-bridges then change shape, pulling the actin
filaments toward the center of the sarcomere.
Muscle
fiber
myofibrills
Sarcomere
Actin &
miosin
Lesson Overview
Control of
muscle)
The Muscular System
Muscle
Motor neuron
Acetylcholine
(neurotransmitter)
Activation of muscle
fibers cell membranes
Release of Ca+ ions
Stimulation of myosin
and actin interaction
Contraction
(skeletal
Lesson Overview
The Muscular System
How Muscles and Bones Interact
Skeletal muscles are joined to bones by the tendons.
Tendons pull on the bones and make them work like levers.
Lesson Overview
The Muscular System
• The joint (where two bones meet) functions as a fulcrum (the
fixed point around which the lever moves)
• The muscles provide the force to move the lever.
Lesson Overview
The Muscular System
How Muscles and Bones Interact
Most skeletal muscles work in opposing pairs—when one muscle
contracts, the other relaxes.
Lesson Overview
The Muscular System
Types of Skeletal Muscle Fibers.
Present in all skeletal muscle and activated depending on need.
Fibers type can be modified.
RED FIBERS (40%)
WHITE FIBERS (60%)
slow contraction velocity
fast contraction velocity
Very resistant to fatigue. Work for
long periods of time
Fatigue easily. Generates more force
Postural muscles of the neck.
Activities that require great strength
or quick bursts of speed, like
sprinting, weight lifting
Lesson Overview
The Muscular System
Exercise and Health
RESTING MUSCLE TONE: state of partial contraction.
Muscle tone keep the back and legs straight and the head upright, even when we
are relaxed.
Muscles that are exercised regularly stay firm and increase in size and strength.