L25 Skeletal Muscle Structure and Function

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Skeletal muscle is essential for movement, posture, and heat generation.

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A muscle cell is made of myofilaments, and the sarcomeres within it are made of myofibrils.

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Myofibrils have around 30,000 sarcomeres.

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( Sarcoplasmic Reticulum, T-tubule(Transverse tubule), Triad ): The ER of the muscle. Stores calcium.
( T-tubule(Transverse tubule), Triad, Sarcoplasmic Reticulum ): invaginated sarcolemma, enhances calcium transport.
( Triad, Sarcoplasmic Reticulum, T-tubule(Transverse tubule) ): T-tubule in between two SR.

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Troponin and tropomyosin attach to myosin, making them part of the thick filament.

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If a motor neuron innervates a large number of muscle fibres, the action is precise.
If a motor neuron innervates a small number of muscle fibres, the action is unprecise.

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Choose the correct statements.

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The mechanism of contraction of skeletal muscles begins with ❌. Here, the ❌ action potential is transferred to a ❌ action potential via the neurotransmitter ACh. (This ACh is diffused through the NMJ when ❌ channels opening in the neuron trigger the release of vesicles.)
Next, ❌ occurs. ACh receptors open voltage gated ❌ channels, which depolarises the muscle membrane (❌). Ca++ is released from the ❌ and diffuses into the firstly the ❌, and then the ❌. Here it forms crossbridges with the myofilaments, allowing them to interdigiate.
After, the muscle ❌ when Ca++ is taken up into the SR and the crossbridges ❌.

excitation

neuronal

muscular

Ca++

contraction

Na+

sarcolemma and T-tubules

SR

sarcoplasm

myofilaments

relaxes

uncouple

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Choose the incorrect statement.

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The sarcolemma depolarises when no new AP innervates it.

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• Understand why we need muscle (cardiac, smooth, skeletal). • Know the structure and molecular components of skeletal muscle and their interaction. • Know the structure and molecular components of motor unit (neuromuscular junction). • Understand the mechanism of contraction

L25 Skeletal Muscle Structure and Function

L25 Skeletal Muscle Structure and Function

Skeletal muscle is essential for movement, posture, and heat generation.

A muscle cell is made of myofilaments, and the sarcomeres within it are made of myofibrils.

Myofibrils have around 30,000 sarcomeres.

Troponin and tropomyosin attach to myosin, making them part of the thick filament.

If a motor neuron innervates a large number of muscle fibres, the action is precise. If a motor neuron innervates a small number of muscle fibres, the action is unprecise.

Choose the correct statements.

Choose the incorrect statement.

The sarcolemma depolarises when no new AP innervates it.

Ca++ ions diffuse back into the SR when the muscle relaxes, and can no longer bind to troponin.

When Ca++ leaves the myofilaments, they uncouple passively.

If a motor neuron innervates a large number of muscle fibres, the action is precise.
If a motor neuron innervates a small number of muscle fibres, the action is unprecise.