Part 1 of 4 Muscle chapter 10

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Part 1 3/27/2016
Kathleen Cercone PT, PhD

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4. 4
3 Main aspects of a muscle
contraction
1.Anatomy and micro anatomy
2.Neuromuscular connection for contraction to
occur
3.Energy needed or nothing goes

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Special Characteristics of Muscle
Tissue
•Excitability, or irritability, is the ability to
receive and respond to a stimulus.
• Contractility is the ability to contract forcibly
when stimulated.
• Extensibility is the ability to be stretched.
• Elasticity is the ability to resume the cells’
original length once stretched

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Myosatellite cell
Immature
muscle fiber
Nuclei
Myosatellite cell
Up to 30 cm
in length
Mature skeletal
muscle fiber
The multinucleate cells begin
differentiating into skeletal
muscle fibers as they enlarge and
begin producing the proteins
involved in muscle contraction.
Over time, most of the myoblasts fuse
together to form larger multinucleate cells.
However, a few myoblasts remain within the
tissue as myosatellite cells, even in adults.
Muscle fibers develop through the
fusion of embryonic mesodermal
cells called myoblasts.
Myoblasts
The development of a skeletal muscle
fiber from myoblast to maturity
Myoblasts fuse, forming cells
Develop into skeletal muscle fibers
Each skeletal muscle fiber nucleus
represents a myoblast
Not all myoblasts fuse into
developing muscle fibers& Some
remain in endomysium and help
muscle repair

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Sarcoplasmic reticulum (SR)
Ca2+
Gated calcium
channel (closed)
Calcium ion
pump
Sarcoplasm
The membrane of the sarcoplasmic reticulum, which contains calcium ion pumps
Transverse tubules (T tubules)
T tubule encircling sarcomere
at zone of overlap
Sarcolemma
Transverse tubule
Terminal cisternae
TriadPosition of M line

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The Organization of a Skeletal Muscle Fiber.
T tubules
Terminal
cisterna
Sarcoplasmic
reticulum Triad Sarcolemma
Mitochondria
Thick
filament
MyofilamentsThin
filament
MYOFIBRIL
The structure of a skeletal
muscle fiber.
SARCOMERE
Z line
Zone of overlap
M line
Myofibril
I band H band
A band
Zone of overlap
The organization of a sarcomere, part of a single myofibril.
Z line M line Z line
A stretched out
sarcomere.
Z line and thin
filaments
Active site
Z line
Actin molecules
Thick filaments
M line
ACTIN
STRAND
Troponin Tropomyosin
Thin filament
MYOSIN MOLECULE
Myosin tail
Myosin
head
Hinge
The structure of a thick filament.
The structure of a thin filament.

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The Organization of a Skeletal Muscle Fiber.
Z line Zone of overlap
M line
Myofibril
I band H band Zone of overlap
A band
SARCOMERE
The organization of a sarcomere, part of a single myofibril.

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Z line Z line

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Sliding Filament Model of Contraction
• Thin filaments slide past the thick ones so that
the actin and myosin filaments overlap to a
greater degree
• In the relaxed state, thin and thick filaments
overlap only slightly
• Upon stimulation, myosin heads bind to actin
and sliding begins

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The Organization of a Skeletal Muscle Fiber.
Z line M line Z line
A stretched out
sarcomere.
Z line and thin
filaments
Z line
Thick filaments
M line

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