Muscle Physiology Quiz

What is the resting membrane potential of a skeletal muscle cell?

• 0 mV

• -70 mV

• -90 mV

• -55 mV

What ion diffuses into the cell causing depolarization during an action potential?

• Ca2+

• K+

• Cl-

• Na+

Which protein binds calcium for muscle contraction to occur?

• Actin

• Myosin

• Tropomyosin

• Troponin

What is the role of ATP in muscle contraction?

• It binds to myosin, releasing it from actin.

• It depolarizes the muscle cell membrane.

• It is broken down to ADP + Pi to depolarize the cell.

• It acts as a second messenger in the cell.

During which phase do muscle fibers develop tension and may shorten?

• Relaxation

• Contraction

• Refractory period

• Hyperpolarization

What causes the end-plate potential (EPP) in muscle cells?

• Hydrolysis of ATP

• Closure of Ca2+ channels

• ACh binding to its receptors and opening Na+ channels

• Opening of voltage-gated K+ channels

What is the immediate effect of the arrival of an action potential at the neuromuscular junction?

• Calcium ions are pumped back into the SR.

• Myosin heads detach from actin.

• Acetylcholinesterase breaks down ACh.

• Calcium channels open and calcium ions diffuse out of the SR.

What is the result of the crossbridge cycling in muscle contraction?

• Sarcomere lengthening

• Sarcomere shortening

• Decrease in muscle tension

• Increase in muscle elasticity

What factor does NOT influence the strength of a muscle twitch?

• Muscle size

• Temperature of the muscles

• Color of the muscle

• State of hydration of the muscle

What is the cause of tetanus?

• An increase in muscle elasticity

• A decrease in ACh at the synaptic knobs

• A toxin from Clostridium tetani

• A decrease in calcium ion concentration