Muscular system Knowledge-Based Download PDF

Questions

1. 1.

   In smooth muscle tissue, contraction is initiated when cytosolic calcium ions bind directly to which of the following proteins?

   • A) Tropomyosin
   • B) Calsequestrin
   • C) Myosin light-chain kinase
   • D) Calmodulin
2. 2.

   During excitation-contraction coupling in a skeletal muscle fiber, action potentials propagate deep into the interior of the cell via which of the following structures?

   • A) Sarcoplasmic reticulum
   • B) Transverse tubules
   • C) Motor end plate
   • D) Z discs
3. 3.

   According to the sliding filament theory, which of the following regions of a skeletal muscle sarcomere remains constant in length during contraction?

   • A) I band
   • B) H zone
   • C) Distance between adjacent Z discs
   • D) A band
4. 4.

   Which of the following events directly causes the myosin head to detach from the actin filament during the cross-bridge cycle of skeletal muscle?

   • A) Hydrolysis of ATP into ADP and inorganic phosphate
   • B) Binding of a new molecule of ATP to the myosin head
   • C) Release of calcium ions from the sarcoplasmic reticulum
   • D) Phosphorylation of troponin by creatine kinase
5. 5.

   During skeletal muscle contraction, which of the following events occurs as a direct result of calcium ions binding to troponin?

   • A) Tropomyosin shifts to expose the myosin-binding sites on actin filaments.
   • B) ATP is hydrolyzed by myosin heads to cock them into a high-energy state.
   • C) Acetylcholine is released into the synaptic cleft at the motor end plate.
   • D) Calcium ions are actively transported back into the sarcoplasmic reticulum.