Mechanism and Characteristics of Muscle Contraction

Acetylcholine receptors are present mainly in which of the following structures?

• Axon terminals

• Motor end plate

• Presynaptic membrane

• Synaptic vesicles

• Terminal cisternae

Troponin and tropomyosin present in skeletal muscles belongs to which one of the

following proteins?

• Contractile

• Nutritional

• Regulatory

• Structural

• Supporting

Which one of the following factors blocks the myosin binding sites on the actin

molecules in a relaxed skeletal muscle?

• ATP

• Calcium

• Tropomyosin

• Troponin C

• Troponin I

Which of the following structures present in sarcomere decreases in length during

the contraction of a skeletal muscle fiber?

• A band

• I band

• Myosin filament

• Actin filament

• Z discs

A cross-sectional view of a skeletal muscle fiber through the H zone would reveal the

presence of which structure?

• Actin and titin

• Actin, but no myosin

• Actin, myosin, and titin

• Myosin and actin

• Myosin, but no actin

Answer explanation

Activation of Dihydropyridine receptors results in which of the following actions?

• Decreased level of calcium ions in cytoplasm

• Entry of sodium ions to motor end plate

• Inactivation of Ryanodine receptor

• Pumping back of calcium into sarcoplasmic reticulum

• Release of calcium from sarcoplasmic reticulum

Which one of the following structures acts as a spring to stabilize the myosin during

contraction?

• Actin

• Titin

• Tropomyosin

• Troponin

• Z disc

In which of the following steps of contraction of skeletal muscle fiber the ATP is

needed?

• Attachment of myosin head with titin

• Binding of calcium ions with troponin

• Detachment of myosin head from actin

• Detachment of tropomyosin with troponin

• Release of calcium from the sarcoplasmic reticulum

Which one of the following actions is mainly responsible for relaxation of skeletal

muscle?

• Closure of post synaptic acetylcholine receptor channel

• Deficiency of acetyl cholinesterase in synaptic cleft

• Pumping of calcium back to sarcoplasmic reticulum

• Removal of acetylcholine from neuromuscular junction

• Removal of calcium from axon terminal

Tilting of the myosin heads and pulling of actin filament represents which

one of the following events in sliding filament theory?

• Cross bridge cycle

• Excitation-contraction coupling

• End plate potential

• Power stroke

• Relaxation of muscle