Download Muscle Tissue

MUSCLE SYSTEM
Human Anatomy and Physiology
Muscle Tissue
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The essential function of muscle is contraction
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Three forms: cardiac, smooth, and skeletal
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In all its forms, muscle makes up nearly half the
body’s mass
Muscle Functions
Producing Movement
2. Maintaining Posture
3. Stabilizing Joints
4. Generating Heat
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Muscle Tissue
In some ways, the three types of muscle tissue
are the same
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All muscle cells are elongated. So they are
all called muscle fibers.
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The ability to contract depends on two types
of myofilaments (actin and myosin)
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Terminology – myo and mys mean muscle;
sarco means flesh
Muscle Tissue
The three types of muscle tissue differ in:
 cell structure
 body location
 how they are stimulated to contract
Three types of Muscle Tissue
Cardiac Muscle
Cardiac muscle is found in only one place in the
body – the heart
 striated
 involuntary
 arranged in spiral or figure 8 shaped bundles
 cardiac muscle fibers are branching cells joined by
special junctions called intercalated disks
 contracts at a fairly steady rate, but the heart can
also be stimulated by the nervous system to shift
into high gear for short periods
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Cardiac Muscle
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The mechanism of contraction in cardiac muscle is
essentially the same as that for skeletal and smooth muscle,
but with some differences.
Cardiac muscle has transverse tubules that supply extra
calcium, and can thus contract for longer periods.
Complex membrane junctions, called intercalated disks,
join cells and transmit the force of contraction from one cell
to the next, as well as aid in the rapid transmission of
impulses throughout the heart.
Cardiac muscle is self-exciting and rhythmic, and the whole
structure contracts as a unit.
Smooth Muscle
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spindle shaped
single nucleus
arranged in layers
One layer usually runs circularly, and the other layer
longitudinally.
 As the two layers alternately contract and relax, they change
the size and shape of the organ
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no striations
involuntary
contractions are steady and tireless
Found in walls of hollow organs such as the stomach,
urinary bladder, and respiratory passages
Skeletal Muscle
cigar-shaped
 multinucleate cells
 striated (appears striped)
 voluntary
 the largest of the muscle fiber types
 contract rapidly and with great force, but tires
easily and must rest after short periods of
activity.
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Smooth Muscles
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Smooth muscle cells are elongated with tapered ends,
lack striations and have a relatively undeveloped
sarcoplasmic reticulum.
 Two types of smooth muscles
1. In multiunit smooth muscle, such as in the blood vessels
and iris of the eye, fibers occur separately rather
than as sheets.
2. Visceral smooth muscle occurs in sheets and is found in
the walls of hollow organs; these fibers can stimulate
one another and display rhythmicity, and are thus
responsible for peristalsis in hollow organs and tubes
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CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Smooth Muscle Contraction
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The myosin-binding-to-actin mechanism is mostly the same
for smooth muscles and skeletal muscles.
Both acetylcholine and norepinephrine stimulate and
inhibit smooth muscle contraction, depending on the
target muscle.
Hormones can also stimulate or inhibit contraction.
Smooth muscle is slower to contract and relax than is
skeletal muscle, but can contract longer using the same
amount of ATP.