Mer Scott
Quiz by , created more than 1 year ago

• 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

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Mer Scott
Created by Mer Scott almost 7 years ago
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L25 Skeletal Muscle Structure and Function

Question 1 of 12

1

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

Select one of the following:

  • True
  • False

Explanation

Question 2 of 12

1

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

Select one of the following:

  • True
  • False

Explanation

Question 3 of 12

1

Myofibrils have around 30,000 sarcomeres.

Select one of the following:

  • True
  • False

Explanation

Question 4 of 12

1

Select from the dropdown lists to complete the text.

( 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.

Explanation

Question 5 of 12

1

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

Select one of the following:

  • True
  • False

Explanation

Question 6 of 12

1

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.

Select one of the following:

  • True
  • False

Explanation

Question 7 of 12

1

Choose the correct statements.

Select one or more of the following:

  • A muscle fibre is innervated by multiple motor neurons.

  • A motor neuron always innervates only one muscle fibre.

  • The more muscle fibres innervated by a neuron, the more precise the movement.

  • None of these are correct.

Explanation

Question 8 of 12

1

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 .

Drag and drop to complete the text.

    excitation
    neuronal
    muscular
    Ca++
    contraction
    Na+
    sarcolemma and T-tubules
    SR
    sarcoplasm
    myofilaments
    relaxes
    uncouple

Explanation

Question 9 of 12

1

Choose the incorrect statement.

Select one of the following:

  • When Ca++ binds to the troponin-tropomyosin complex, it changes its composition, to open the binding site for myosin.

  • Myosin is in an energised state before Ca++ enters.

  • ATP is released when the myosin moves in its power stroke.

  • Myosin binding to the open site on actin is the formation of the crossbridge.

Explanation

Question 10 of 12

1

The sarcolemma depolarises when no new AP innervates it.

Select one of the following:

  • True
  • False

Explanation

Question 11 of 12

1

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

Select one of the following:

  • True
  • False

Explanation

Question 12 of 12

1

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

Select one of the following:

  • True
  • False

Explanation

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