Mechanism of contraction in skeletal muscle

In the mechanism of skeletal muscle contraction, which of the following event occurs first?

• Cross-bridge cycle

• Calcium ion release from sarcoplasmic reticulum

• Generation of action potential

• Opening of the sarcoplasmic reticulum Ca2+ATPase (SERCA)

Answer explanation

Events at the neuromuscular junction leads to the generation of action potential. Action potential depolarizes the skeletal muscle cell membrane, and excitation event proceeds.

Depolarization of T-tubules lead to

• muscle contraction

• generation of action potential

• Ca²⁺ binds to troponin C

• conformational changes of DHP receptor

Ca²⁺ released by sarcoplasmic reticulum will bind to

Which regulatory protein covers the myosin binding sites on the actin molecules?

• Troponin

• Tropomyosin

• Calmodulin

• Connectin

Which of the following must happen to detach the cross-bridge between actin and myosin

• Binding of ATP to actin

• Binding of ADP to myosin

• Binding of ATP to myosin

• Hydrolysis of ATP

Which of the following occur when ATP binds to the myosin head?

• Myosin head change to low energy configuration

• Myosin head forms cross bridge

• Myosin head undergoes power stroke

• Myosin head detach from actin

A power stroke is when

• new Ca²⁺ binds to a new troponin

• ATP is bound to myosin head

• there is conformational changes of the myosin head

• myosin binds to a new site on actin

During muscle contraction, the 'Z' lines

• disappear

• get closer together

• get farther apart

• overlapping each other

During muscle contraction, the width of the 'A' band

• decreases

• increases

• does not change

During muscle contraction, the width of the 'I' band

• decreases

• increases

• does not change