Skeletal Muscle Skeletal Muscle Anatomy Figure 12-3a-2: ANATOMY SUMMARY: Skeletal Muscle.
Skeletal Muscle- Excitation
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Transcript of Skeletal Muscle- Excitation
Skeletal Muscle- Excitation
Prof. K. Sivapalan
Skeletal Muscle Excitation 2
Muscle Types
• Skeletal muscle- attached to skeleton
• Striated muscle- striations under light microscope. [40% of the body, other types 10 %].
• Smooth muscles- no striations- many subtypes.
• Cardiac muscle- found in heart, striated but different from skeletal muscles
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Muscle Structure• Skeletal muscles connect two structures (bones)
through tendons or directly.
• Muscle cell is known as muscle fiber, 10-80 µ in diameter, extending from one end to the other end of the muscle.
• It is multinucleated, rich in mitochondria, full of myofibrils.
• Innervated by one axon at its middle through the motor-end plate.
• Sarcolemma is excitable as nerves. [RMP -90]
• Sarcoplasmic reticulum forms a tubular system that transmits the action potential into the sarcoplasm.
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Skeletal Muscle
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Myofibrils
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Myofibrils
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Motor End Plate
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Stimulation of the Muscle
• Action potential reaches the motor end plate
• Calcium entry into axonal terminal
• Release of acetyl choline
• Ligand gated channels- increase Na+ entry- threshold level
• Action potential spreads along the sarcolemma
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Sarcotubular System
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Excitation – Contraction Coupling
• Action potentials spread along the Transverse tubular system.
• The terminal cisterns release Ca++
• Calcium ions facilitate binding of actin and myosin.
• Calcium is transported back into sarcoplamic reticulum and back into terminal cistern.
• Removal of calcium results in relaxationJune 2013