Muscular System: Part 3

Which ions are released from the sarcoplasmic reticulum to initiate contraction?

• Calcium

• Sodium

• Potassium

• Phosphorous

Which protein does calcium bind to in the beginning stages of muscle contraction?

• Troponin

• Tropomyosin

• Actin

• Myosin

What is the result of calcium binding to a protein on the thin filament?

• Active sites on actin molecules are exposed

• Active sites on actin molecules are covered up

• Muscle relaxation occurs

• Sarcomeres elongate

What is the name of the linkage between actin and myosin?

• Cross-bridge

• Cross-channel

• Bypass

• Sarcoplasmic reticulum

What happens after myosin links with actin?

• Thin filaments are pulled toward the center of the sarcomere

• Thin filaments are pulled away from the center of the sarcomere

• Thick filaments are pulled toward the center of the sarcomere

• Thin filaments are pulled away from the center of the sarcomere

Once a myosin head has linked with one actin active site, it cannot bind to another actin active site.

• True

• False

When does relaxation occur?

• When action potentials (signals) no longer reach the muscle cell

• When action potentials (signals) reach the muscle cell rapidly

• When action potentials (signals) tell the muscle to stop contracting

• When acetylcholine enters the muscle cell

Which enzyme breaks down acetylcholine so that relaxation can occur?

• Acetylcholinesterase

• Lactase

• Salivary amylase

• Nuclease

Where do calcium ions go during relaxation?

• Sarcolemma

• Sarcoplasm

• Sarcoplasmic reticulum

• Saturn

Which molecule is responsible for breaking cross-bridges?

• ATP

• Calcium

• Acetylcholine

• Adrenaline