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• Describe the characteristics & functions of muscle tissue.

• Describe organization of muscle tissue.

• Identify the components of the sarcomere.

• Identify components of the neuromuscular junction.

• Explain steps in skeletal muscle contraction.

• Relate microscopic function to macroscopic function.

Class 9Muscle Tissue- Anatomy& Contraction

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Muscle organization

3

Formation of skeletal muscleMyoblast fusion

•Multinucleate

•Syncytial

satellite

T tubules

myofibril

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Myofilaments

Thick (myosin)

Thin (actin)

“Sliding filament hypothesis” vs. “Shortening filament hypothesis”

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Formation & membranesMyoblast fusion

•Multinucleate

•Syncytial

satellite

T tubules

myofibril

SR

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Sliding filaments

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Organization

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Actin & myosin

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Sliding filament theory

30% shorter

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Neural control

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Troponin blocks actin w/o Ca++

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Ca++ troponin to release actin

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Myosin head binds actin

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Myosin head turns, release ADP

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Pivoting causes shortening, ATP binding causes release

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ATP binds & loads myosin head

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Initial length & max. tension

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Overall lessons:• Muscle has many functions, principle of which is shortening.

• Muscles are made of fascicles of muscle fibers (cells).

• Muscles are covered and contain CT membranes w/ vessels & nerves.

• Muscle fibers are giant syncytial, multinucleate cells.

• Myofilaments are protein fibers that slide past each other to cause shortening.

• The S.R. stores Ca++, and releases Ca++ to facilitate cross-connections between the sliding filaments.

• The pattern of fiber connections is governed by mutually exclusive binding sites (troponin either Ca++ or actin; myosin either actin or ATP).

• Relaxation only possible by removing ACh & Ca++.