Download 12/02/13 - Muscle1

Title: Muscle Tissue
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Although bones provide leverage for the body and form its framework it
cannot move by itself
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Movement results from the alternate contraction and relaxation of primarily
skeletal muscle, which makes up 40 – 50% of the total body weight
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The muscles primary job is to convert chemical energy into mechanical
energy to generate force, perform work and provide movement
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Muscle tissue
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1- Types of Muscle
a- There are three types of muscle tissue – skeletal, cardiac and smooth
2- Skeletal Muscle
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3- Cardiac muscle
a- Found only in the heart
b- Looks like skeletal muscle but acts involuntarily
c- Has a built in autorhythmicity (sets it own pace)
d- Controlled by the autonomic nervous system
e-
Contains intercalated discs - Intercalated discs support synchronized
contraction of cardiac tissue. They occur at the Z line of the
sarcomere and can be visualized easily when observing a longitudinal
section of the tissue.
4- Smooth Muscle
abcd5- Functions of Muscle
a- Provide body movement – Large and small movements of the body depends
upon the interaction of muscle, joints and bones
b- Stabilizing body position –
c- Storing and moving substances – Sustained contractions of ring-like structures
called sphincters prevent the outflow of contents from hollow organs (pyloric
sphincter, upper and lower esophageal sphincter, sphincter of oddi, urinary
sphincter) Contraction and relaxation regulates the flow of blood and food
through various systems, smooth muscles move sperm and egg through the
reproductive tract
d- Generates heat –
6- Properties of Muscle
a- Muscle has four special properties that enable it to function and contribute to
homeostasis
1- Electrical excitability –
2- Contractility –
3- Extensibility –
4- Elasticity – The ability to return to its original length and shape after
contraction or extension
7- Connective tissue components
a- Three layers of connective tissue surrounds, protect and strengthen skeletal
muscle. Theses layers are important because they form tendons at the end of
the muscle which connects it to bone
b- Aponeurosis –
8- Nerve and blood supply to blood
a- All skeletal muscle is highly innervated with nerve and has a significant blood
supply
b- Afferent -
c- Efferent –
d- Each muscle fiber comes into contact with one or more capillaries. The
capillary is the site of gas exchange
9- Muscle size
a- Hypertrophy -
b- Hyperplasia –
c- Atrophy –
d- Sarcolemma – The sarcolemma is the plasma membrane of the muscle fiber.
Within the sarcolemma are invaginations called T-tubules, which are filled
with interstitial fluid. This system allows electrical signals to propagate
throughout the muscle
10- Sarcomere – The sarcomere is the basic structural unit of the myofibril. The
myofibril is the main contractile element of the muscle fiber
a- Each myofibril is about 2 microns (1 x 10-6) and runs the entire length of the
fiber
b- Within the myofibrils are thick and thin filaments (primarily consisting of
proteins)
c- The thick and thin filaments overlap each other to a greater or lesser extent,
depending on whether or not the muscle is relaxed, contracted or extended
d- This overlap contributes to a variety of zones and bands that create the
striations seen in skeletal muscle
e- These zones and bands are all collectively found with in the sarcomere
f- The sarcomere is separated and connected to the next sarcomere by zigzagging Z-discs. A sarcomeres length is measured from Z-disc to Z-disc
g- The darker middle region of the sarcomere is the A-band which extends the
entire length of the thick filament
h- A narrow H-zone extends the entire length of the thick filament but contains
no thin filaments
i- Toward the end of each A band is the region of overlap, where thick and thin
filaments lie next to each other
j- The I-band contains thin but no thick filaments
k- The Z-disc passes though the center of each I-band
l- The M-line is found in the center of the sarcomere, it contains support proteins
that hold the thick filaments together
m- Diagram