Topic 8 pt 2

What causes the influx of Na⁺ and local depolarization in muscle cells?

• Binding of calcium

• Binding of acetylcholine

• Binding of potassium

• Binding of glucose

What triggers the opening of voltage-gated Na⁺ channels?

• Local hyperpolarization

• Local depolarization

• Local repolarization

• Local stabilization

What is the term used for the wave of depolarization spreading over the plasma membrane of the muscle cell?

• Hyperpolarization

• Action potential

• Resting potential

• Equilibrium potential

What role do ryanodine receptors play in muscle contraction?

• They block Na⁺ channels

• They "plug" sarcoplasmic reticulum

• They release acetylcholine

• They bind to actin

What happens when the sarcolemma depolarizes?

• Ryanodine receptors remain unchanged

• Ryanodine receptors undergo conformational change

• Calcium channels close

• Sodium channels close

Where does Ca²⁺ flow after being released from the sarcoplasmic reticulum?

• Into the mitochondria

• Into the sarcoplasm

• Into the nucleus

• Into the Golgi apparatus

What does Ca²⁺ bind to in order to initiate muscle contraction?

• Actin

• Myosin

• Troponin

• Tropomyosin

What change occurs in troponin when Ca²⁺ binds to it?

• It undergoes conformational change

• It releases ATP

• It binds to myosin

• It breaks down

What is the result of the conformational change in troponin?

• Tropomyosin binds to actin

• Tropomyosin moves away from myosin binding sites

• Tropomyosin breaks down

• Tropomyosin binds to myosin

What is the function of myosin in muscle contraction?

• It binds to calcium

• It binds to actin

• It binds to troponin

• It binds to tropomyosin