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Ch 9 Muscular System
Naming of Muscles
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Preview the outline: What do you notice about
the names of the muscles?
Muscle nomenclature
•
•
•
•
Directional
e.g. Lateralis, medialis
Specific regions
e.g. abdominus, brachialis, oculoOrigin
e.g. biceps, triceps, quadriceps
Shape
e.g. deltoid, orbicularis, serratus, trapezius
• Other features
e.g. brevis, longus, magnus
• Actions
e.g. abductor, adductor, flexor, extensor
• Specific references
e.g. buccinator (trumpeter), sartorius (like a
tailor)
Musculoskeletal System
• Movement occurs from the
•
interaction between muscles & bones
is made up of:
 muscles
 bones
 joints
What would you NOT be
able to do if you lacked
muscles?
A) Muscle Functions
1. Produce body movements
2. Stabilize body positions
standing, sitting
maintaining posture
3. Regulate volume contents in
organs
e.g. sphincter muscles prevent
outflow of stomach
4. Move substances (internally)
Cardiac muscle-moves blood through
blood vessels
Smooth muscle-moves food &
urine/feces, push gametes, regulate
blood flow through blood vessels
Skeletal muscle-helps return blood
back to heart
5. Produce heat
B) Types of Muscles
1. Skeletal muscle- attach to bones &
moves part of the skeleton
 striated, long cells
 multinucleated
 voluntary
2. Cardiac muscle- found only in heart
 striated, branched cells
 intercalated disks
 involuntary
3. Smooth muscle- found in walls of
hollow organs (stomach, intestines),
blood vessel walls, airways
 not striated
 tapered ends
 involuntary
Attachments and Actions
• Movement usually produced by a group
of muscles
Prime mover (agonist) – muscle
responsible for most of the movement
 Synergists – muscles that help the prime
mover by stabilizing joints
 Antagonist – muscle that produces
movement opposite to prime mover


22-12
Relaxes when prime mover contracts
C) Skeletal Muscle
C) Skeletal Muscle
• is composed of muscle fibers,
connective tissue, nerves & blood
vessels
• Skeletal muscles are highly vascularized.
 to provide O2 & nutrients to muscle tissue
for contraction & to get rid of waste
• Skeletal muscles are also highly innervated.
 to signal muscles to contract
D) Overall Organization of a Skeletal Muscle
Figure 8.1
1. Epimysium (connective tissue)
surrounds entire skeletal muscle
 each muscle is composed of
10-100 fascicles
2. Perimysium surrounds each
fascicle
Each
fasicle is a bundle of
muscle fibers (muscle cells)
3. Endomysium surrounds each
muscle fiber (muscle cell)
 Each
muscle fiber is composed
of 100s-1000s of myofibrils
A “Typical” Eukaryotic Animal Cell
Tendon: an extension of epi, peri
& endomysium beyond the muscle
that attaches the muscle to the
bone
4. Each myofibril is composed of
actin & myosin protein filaments.
E) Anatomy of a Skeletal Muscle Cell
1. muscle fiber = is an elongated muscle
cell
2. sarcolemma = the plasma membrane of
each muscle fiber
3. transverse or T- tubules = tunnels that
starts at the sarcolemma & branch to
the center of each muscle fiber

conduct impulses throughout the muscle
fiber
4. Muscles cells are multi-nucleated
5. Muscles cells have many mitochondriato produce ATP (energy) via cellular
respiration for muscle contraction
6. sarcoplasmic reticulum is a network
of fluid filled membrane tubules;
stores Ca ions
7. sarcoplasm contains myoglobin, a red
pigmented protein that carries oxygen
8. myofibrils are made of protein
filaments:
 thick filaments = myosin
 thin filaments = actin
9. A sarcomere is a section of a
myofibril that is the basic unit of
contraction
Figure 8.2a
Structure of a Sarcomere
1. Filaments overlap in repeating patterns
2. Sarcomeres are separated by Z-discs
3. A-band = region of thick filaments;
appears darker
4. H-zone = center of A-Band; thick
filaments ONLY
Structure of a Sarcomere
1. Filaments overlap in repeating patterns
2. Sarcomeres are separated by Z-discs
3. A-band = region of thick filaments;
appears darker
4. H-zone = center of A-Band; thick
filaments ONLY
5. I-band = region of thin filaments ONLY
6. Striations due to the alternating dark &
light bands
1
2
3
1
2
3
Figure 8.2c
Myosin (thick filament)
Figure 8.3a
pain has started means a heart attack is unlikely.
Actin (thin filament)
Thin filaments are made of:
a) actin
b) tropomyosin—blocks myosin-binding site
& prevents contraction (= relaxed muscle)
c) troponin—holds the tropomyosin strands
in place
Figure 8.4