Muscle Contraction Quiz

What is the role of calcium ions in cross-bridge formation?

• Moving the actin filaments towards the centre of the sarcomere

• Swiveling the myosin heads

• Exposing the binding sites for the myosin heads

• Breaking the cross-bridge between actin and myosin

What causes the myosin heads to change position and swivel?

• Acetylcholine release into the motor end plate

• Depolarisation of the sarcolemma

• Calcium ions binding to troponin

• ATP binding to the myosin head

What is the function of ATP in the sliding mechanism of actin and myosin?

• Moving the actin filaments towards the centre of the sarcomere

• Causing the myosin heads to change position and swivel

• Exposing the binding sites for the myosin heads

• Breaking the cross-bridge between actin and myosin

What happens as actin filaments are anchored to Z lines?

• The dragging of actin pulls the Z lines closer together

• The muscle fibres as a whole contracts

• The sarcomeres become shorter in length

• The repeated reorientation of the myosin heads

What is the role of troponin and tropomyosin in muscle contraction?

• Covering the binding sites for the myosin heads

• Exposing the binding sites for the myosin heads

• Breaking the cross-bridge between actin and myosin

• Swiveling the myosin heads

What is the effect of ATP hydrolysis on the myosin heads?

• Causing the myosin heads to change position and swivel

• Moving the actin filaments towards the centre of the sarcomere

• Breaking the cross-bridge between actin and myosin

• Exposing the binding sites for the myosin heads

What causes the muscle contraction?

• The repeated reorientation of the myosin heads

• The sliding of actin along myosin

• The sarcomeres become shorter in length

• The dragging of actin pulls the Z lines closer together

What is the function of the myosin heads in muscle contraction?

• Breaking the cross-bridge between actin and myosin

• Moving the actin filaments towards the centre of the sarcomere

• Exposing the binding sites for the myosin heads

• Swiveling and changing orientation