Anatomy of a Muscle
I). Functions of Skeletal Muscle
| Movement |
| Posture |
| Stabilizes joints |
| Heat |
| Protects organs |
II). Terms
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Excitability |
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Contractility |
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Extensibility |
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Elasticity |
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| origin & insertion | direct & indirect attachments |
III). Attachments
A). Insertion: moves the bone.
B). Origin: does not move or is less movable.
C). Direct attachments: the connective tissue fuses to the bone.
D). Indirect attachments: outer connective tissue forms a tendon that connects to the bone
IV). Muscle Structure
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A). Muscle
B). Fascicle
C). Muscle Fiber: Cell
sarcolemma = plasma membrane
D). Myofibril: Organelle
E). Sarcomere: Contractile unit
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F). Myofilaments
Actin
Myosin
V). Bands of the Muscle Fiber
A). Muscle fiber:
1). Dark A bands: The thick myosin filaments extend the length of the A band.
2). Light I bands: The thin actin filaments extend the length of the I band & part of the A band
B). Myofibril
1). A band
a). H zone: Lighter stripe
b). M line: bisects the H zone
2). I band
a). Z disc midline
Sarcomere is the area between 2 Z discs.
During muscle contractions the I band shortens
and the Z discs move closer together.
VII). Myofilament Composition
A). Thick filament (MYOSIN)
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| The 2 heads contain ATP binding sites & link the actin and myosin together during contraction. |
B). Thin Filaments (ACTIN)
| Binds to the myosin heads. |
| Active sites are blocked when the muscle is relaxed. |
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