Steps of Muscle Contraction

How does the sarcomere shorten (contract) ?

• The myosin filaments contract

• The actin filaments contract

• The myosin is pulled by the actin

• The actin is pulled by the myosin

What is the name of the protein that covers the binding sites on actin?

• Myosin

• Titin

• Troponin

• Tropomyosin

___ and ___ are regulatory proteins bound to actin.

• Myosin and actin

• Glycogen and hemoglobin

• Calcium and oxygen

• Troponin and tropomyosin

The neurotransmitter that signals muscle contraction is...

• Calcium

• Actin

• Myosin

• Ach (acetylcholine)

What is the name of structure #2?

• Troponin

• Tropomyosin

• Actin

• ATP

Which of the following steps occurs FIRST in the excitation phase of muscle contraction?

• Sodium ions enter the muscle fiber.

• Calcium ions bind to troponin.

• Acetylcholine binds to receptors on the motor end plate.

• Calcium channels in the axon terminal open.

What happens to the Z-discs during muscle contraction, according to the sliding filament theory?

• They move apart from each other.

• They move toward the M-line.

• They break down.

• They move toward the A-band.

What is the role of thin filaments during muscle contraction?

• They remain stationary while thick filaments move.

• They slide toward the center of the sarcomere.

• They detach from the Z-discs.

• They shorten, causing the sarcomere to expand.

What is the role of calcium ions in muscle contraction?

• They bind to myosin heads.

• They bind to troponin, causing a conformational change.

• They provide energy for the contraction.

• They break down ATP.

Which molecule provides the energy required for muscle contraction?

• ATP

• ADP

• GTP

• CTP