Download The Muscular System

The Muscular System
MUSCULAR SYSTEM
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Types of Muscle Tissue: Skeletal,
Smooth, and Cardiac
Skeletal, aka “striated”
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voluntary – attached to bones and under
conscious, willful control.
Has the ability to contract (shorten) and
thereby bring about movement
Cardiac Muscle
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Found only in the heart
Striated
Involuntary
Cells connected by intercalated disks
Smooth Muscle
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Not striated
Involuntary
Walls of hollow organs such as:
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Stomach, urinary bladder, respiratory
passages
Arranged in sheets/layers
Muscle Functions
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Producing Movement
Maintaining Posture
Stabilizing Joints
Generating Heat
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Maintaining body temperature
Muscle and Muscle Fiber
Structure:
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A muscle is composed of many muscle
fibers (muscle fiber = muscle cell).
The individual muscles are separated
from each other and held in place by a
covering called the FASCIA.
This fascia also forms TENDONS
connecting muscles to bones.
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The muscle fiber membrane is called
the SARCOLEMMA and the cytoplasm is
called the SARCOPLASM.
Within the sarcoplasm are many parallel
fibers known as MYOFIBRILS.
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Each myofibril is made of many protein
filaments called MYOFILAMENTS. There
are two types:
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MYOSIN – thick filaments
ACTIN – thin filaments
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Actin and Myosin filaments are arranged in an
overlapping pattern of light (“I” bands) and dark
(“A” bands).
In the middle of each “I” band is a line called a
“Z” line.
The section of a myofibril from one Z-line to the
next Z-line is called a SARCOMERE.
The arrangement of these sarcomeres next to
each other produces the STRIATIONS of the
skeletal muscle fibers.
How do muscles contract?
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Stimulated by nerve impulses to contract
Sliding Filament Theory
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Muscle cell becomes excited – action potential
Flood of calcium
Myosin heads bind to thin filaments
Form “cross bridges”
Heads bend and pull thin filaments together
Muscle shortens – contracting!
Video animation of muscle contraction