Actin Myosin

During muscle contraction, what happens to the sarcomere length?

• It increases.

• It decreases.

• It remains the same.

• It doubles.

Which of the following best describes the sliding filament mechanism?

• Actin filaments slide over myosin filaments, shortening the sarcomere.

• Myosin filaments slide over actin filaments, shortening the sarcomere.

• Actin and myosin filaments slide past each other without changing the length of the sarcomere.

• Actin and myosin filaments shorten, causing the sarcomere to contract.

What is the role of calcium within the sarcomere?

• calcium ends the contraction process.

• calcium binds to myosin, initiating muscle contraction.

• calcium binds to troponin, initiating muscle contraction.

• calcium ions depolarise the sarcolemma

What is the function of tropomyosin in muscle cells?

• It binds calcium to initiate contraction.

• It serves as a binding site for the myosin head.

• It blocks the myosin-binding sites on actin when the muscle is relaxed.

• It converts ATP to ADP to provide energy for muscle contraction.

How do myosin and actin interaction during muscle contraction?

• Myosin moves to bind to actin to form a crossbridge

• Actin moves to bind with myosin to form a crossbridge

• Myosin repels actin filaments, causing them to slide apart.

• Actin repels myosin filaments, causing them to slide apart.

What causes the power stroke during the cross bridge cycle?

• The attachment of ATP

• The breakdown of ATP to ADP and inorganic phosphate

• The release of ADP

• The release of inorganic phosphate

What happens when ATP binds to the myosin head?

• The myosin head immediately detaches from actin.

• The myosin head becomes more firmly attached to actin.

• The myosin head changes shape, causing the power stroke.

• The myosin head splits ATP into ADP and inorganic phosphate.

Which would cause neurotransmitter release at the neuromuscular junction?

• Influx of calcium

• Influx of potassium

• Efflux of calcium

• Efflux of potassium

Which neurotransmitter is released at the neuromuscular junction?

• Glutamate

• NMDA

• Noradrenalin

• Acetylcholine