Transcript Document

10
Skeletal Muscle
Tissue
PowerPoint® Lecture Presentations prepared by
Leslie Hendon
University of Alabama, Birmingham
© 2014 Pearson Education, Inc.
I. Muscle
A. Muscle = a Latin word for “little mouse”
1. skeletal muscle
2. cardiac muscle tissue
3. smooth muscle tissue
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Properties of Muscle Tissue
Contractility
► Myofilaments are responsible for shortening of muscles cells
► Actin and myosin are two type of myofilaments
Excitability
► Nerve signals excite muscle cells
Extensibility
► Contraction of a skeletal muscle stretches the opposing muscle
► Smooth muscle is stretched by substances within that hollow organ
► Food in stomach; urine in urinary bladder
Elasticity
► Recoils after being stretched
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II. Terminology Specific to Muscle Tissue
A. Myo- and mys- - prefixes meaning “muscle”
B. Sarco—prefix meaning “flesh”
1. Sarcolemma - plasma membrane of muscle cells
2. sarcoplasm—cytoplasm of muscle cells
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III. Functions of Muscle Tissue
A. Produce movement
1. skeletal muscle - attached to skeleton (movement)
e.g. biceps, triceps
2. smooth muscle - squeezes fluids through hollow organs
e.g. walls of intestines and arteries
B. Maintain posture and stabilize joints
1. enables the body to remain sitting or standing
2. muscle tone helps stabilize many synovial joints
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C. Heat generation
1. muscle contractions produce heat
2. helps maintain normal body temperature
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IV. Types of Muscle Tissue
A. Skeletal muscle tissue
1. packaged into skeletal muscles
2. makes up 40% of body weight
3. cells are striated
4. innervated by voluntary division of the nervous system
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C. Cardiac muscle tissue
1. occurs only in the walls of the heart
2. cells are striated
3. contraction is involuntary
D. Smooth muscle tissue
1. occupies the walls of hollow organs
2. cells lack striations
3. innervated by involuntary division of the nervous system
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V. Gross Anatomy of a Skeletal Muscle
A. Sheaths of connective tissue
1. epimysium - surrounding entire muscle
2. perimysium - surrounds each fascicle (bundle of fibers)
3. endomysium - wrapping each muscle cell
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Epimysium
Bone
Epimysium
Perimysium
Endomysium
Tendon
Muscle fiber
in middle of
a fascicle
Blood vessel
Fascicle
(wrapped by perimysium)
Endomysium
(between individual
muscle fibers)
Epimysium
Perimysium
Fascicle
Endomysium
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Muscle fiber
B. Each skeletal muscle supplied by branches of
► one nerve
► one artery
► one or more veins
C. Nerves and vessels branch repeatedly
D. Smallest branches serve individual muscle fibers
E. Muscle attachments
► origin - less movable attachment
► insertion - more movable attachment
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Muscle contracting
Origin
Stable
Insertion
moving
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F. Muscles attach by connective tissue (CT)
1. fleshy attachments - CT fibers are short
2. indirect attachments - CT forms a tendon or aponeurosis
G. Bone markings present where tendons meet bones
► tubercles
► trochanters
► crests
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H. skeletal muscle cell (fiber)
1. fibers are long and cylindrical
► Are huge cells—diameter is 10–100 µm
► Length—several centimeters to dozens of centimeters
2. cells are multinucleate
3. nuclei are peripherally located
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Muscle >>> Fascicle >>> Muscle Cell >>> Myofibril
Myofibrils
► Are long rods within cytoplasm
► Make up 80% of the cytoplasm
► Are a specialized contractile organelle found in muscle tissue
►Are a long row of repeating segments called sarcomeres
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Muscle Cell >>> Myofibril
Sarcolemma
Muscle cell 
Mitochondrion
Myofibril
Dark A band Light I band
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Nucleus
Myofibril >>> Sarcomeres
Thin (actin)
filament
Thick (myosin)
filament
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Z disc
I band
H zone
A band
Sarcomere
Z disc
I band
M line
VI. Sarcomeres
A. Basic unit of contraction of skeletal muscle
Z line - boundaries of each sarcomere
► Thin (actin) filaments—from Z disc to center of the sarcomere
► Thick (myosin) filaments—located in the center of the sarcomere
A bands - full length of the thick filament
H zone - center part of A band where no thin filaments occur
M line - in center of H zone
I band - region with only thin filaments
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muscle cell
Sarcolemma
Mitochondrion
Myofibril
Dark A band
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Light I band
Nucleus
myofibril
Thin (actin)
filament
Thick (myosin)
filament
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Z disc
I band
H zone
A band
Sarcomere
Z disc
I band
M line
sarcomere
Z disc
M line
Z disc
Thin (actin)
filament
Elastic (titin)
filaments
Thick
(myosin)
filament
Myosin
heads
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VII. Sarcoplasmic Reticulum and T Tubules
A. Sarcoplasmic reticulum
1. specialized smooth ER
2. contains calcium ions - released when muscle is stimulated
3. calcium ions diffuse through cytoplasm
► Trigger the sliding filament mechanism
B. T tubules - deep invaginations of sarcolemma
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Sarcoplasmic Reticulum and T Tubules
Part of a skeletal
muscle fiber (cell)
I band
Z disc
A band
H zone
I band
Z disc
M
line
Myofibril
Sarcolemma
Sarcolemma
T Tubules of
the sarcoplasmic
reticulum
Myofibrils
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VIII. Mechanism of Contraction
A. Two major types of contraction
1. Concentric contraction – force as muscle shortens
2. Eccentric contraction - force as muscle lengthens
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Sliding Filament Mechanism of Contraction
Thick (myosin)
filament
Thin (actin)
filament
Thin (actin)
filament
Thin (actin) filament
Movement
Myosin
head
Thick (myosin) filament
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Thick (myosin)
filament
Myosin
heads
Sliding Filament Mechanism of Contraction
1 Fully relaxed sarcomere of a muscle fiber
Z
I
H
A
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2 Fully contracted sarcomere of a muscle fiber
Z
Z
I
I
Z
A
I
Muscle >>> muscle fiber
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muscle fiber >>> myofibril >>> sarcomere
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sarcomere
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IX. Innervation of Skeletal Muscle
A. Motor neurons innervate skeletal muscle tissue
1. neuromuscular junction - nerve ending meets muscle fiber
2. Terminal boutons (axon terminals)
► Located at ends of axons
► Store neurotransmitters
3. Synaptic cleft - between axon terminal and sarcolemma
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neuromuscular junction
Terminal bouton of nerve
Synaptic
cleft
Terminal
cistern of SR
Triad
Muscle fiber
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Motor unit = motor neuron and muscle cells innervated
Spinal cord
Motor
unit 1
Motor
unit 2
neuromuscular
junctions
Nere
Motor neuron
cell body
Motor
neuron
axon
Muscle
Muscle
fibers
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Branching axon
to motor unit
X. Types of Skeletal Muscle Fibers
A. Skeletal muscle fibers categorized according to two characteristics
1. how they manufacture energy (ATP)
2. how quickly they contract
B. Oxidative fibers - produce ATP aerobically
C. Glycolytic fibers - produce ATP anaerobically by glycolysis
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D. Slow oxidative fibers
► Red slow oxidative fibers
E. Fast glycolytic fibers
► White fast glycolytic fibers
F. Fast oxidative fibers
► Intermediate fibers
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G. Slow oxidative fibers
► Contract slowly and resistant to fatigue
► Red color due to abundant myoglobin
► Obtain energy from aerobic metabolic reactions
► Contain a large number of mitochondria
► Richly supplied with capillaries
► Fibers are small in diameter
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H. Fast glycolytic fibers
► Contract rapidly and tire quickly
► Contain little myoglobin and few mitochondria
► About twice the diameter of slow oxidative fibers
► Contain more myofilaments and generate more power
► Depend on anaerobic pathways
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I. Fast oxidative fibers
► Contract quickly like fast glycolytic fibers
► Somewhat fatigue resistant
► Have an intermediate diameter
► Are oxygen dependent
► Have high myoglobin content and rich supply of capillaries
► More powerful than slow oxidative fibers
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Skeletal vs. Cardiac vs. Smooth Muscle
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Skeletal vs. Cardiac vs. Smooth Muscle
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Skeletal vs. Cardiac vs. Smooth Muscle
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Skeletal vs. Cardiac vs. Smooth Muscle
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XI. Disorders of Muscle Tissue
A. Muscular dystrophy
1. a group of inherited muscle destroying disease
► Affected muscles enlarge with fat and connective tissue
► Muscles degenerate
► Types of muscular dystrophy
a. Duchenne muscular dystrophy
b. Myotonic dystrophy
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B. Fibromyalgia
► A mysterious chronic-pain syndrome
► Affects mostly women
Symptoms
fatigue
sleep abnormalities
severe musculoskeletal pain
headache
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XII. Formation of Skeletal Muscle Cell
Embryonic
mesoderm cells
1
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Myotube
(immature
multinucleate
muscle fiber)
Myoblasts
2
Satellite cell
3
Mature
skeletal
muscle
fiber