Muscle Contraction and Structure

What is the contractile unit of skeletal muscle?

• Fascicle

• Myofibril

• Sarcomere

• Muscle fiber

Which protein is responsible for splitting the H zone in a sarcomere?

• Myomesin

• Troponin

• Tropomyosin

• Titin

What is the function of the Z disc in a sarcomere?

• To split the I bands

• To split the A bands

• To bind calcium ions

• To connect the thin filaments

Which protein is found in the thick filaments of a sarcomere?

• Actin

• Tropomyosin

• Troponin

• Myosin

What is the role of tropomyosin in muscle contraction?

• To bind calcium ions

• To block myosin binding sites

• To form cross bridges

• To release acetylcholine

What is the function of the sarcoplasmic reticulum?

• To store and release calcium ions

• To produce ATP

• To bind actin

• To regulate membrane potential

What is the role of the T tubules in muscle contraction?

• To release acetylcholine

• To store ATP

• To regulate calcium levels

• To propagate the action potential

What happens during depolarization of a muscle fiber?

• Sodium ions enter the cell

• Potassium ions enter the cell

• Calcium ions enter the cell

• Acetylcholine is released

What causes the myosin binding sites on actin to become available?

• Binding of calcium ions to troponin

• Depolarization of the muscle fiber

• Release of acetylcholine

• Opening of potassium channels

What initiates the process of muscle contraction?

• Release of acetylcholine

• Depolarization of the sarcolemma

• Binding of myosin to actin

• Increase in calcium levels