NM - Excitation-Contraction Coupling (ECC)

What is a sarcomere?

• Basic contractile unit of muscle present in the myofibril

• Myofibril

• Muscle Fascicle

• Muscle Fiber

What are the two main filaments in a sarcomere that cause muscle contraction (by the filaments sliding onto each other)?

• Actin and Myosin

• Troponin and Tropomyosin

• Acetyl Choline and Titin

• Calcium and Sodium

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

• Troponin and tropomyosin both block calcium from entering the muscle cell.

• Troponin helps move tropomyosin to uncover binding sites on actin when calcium is present.

• Tropomyosin directly causes muscle contraction by binding to myosin.

• Troponin and tropomyosin make muscles contract without needing calcium.

What triggers the release of calcium ions inside a muscle cell to cause contraction?

• The breakdown of ATP molecules.

• The arrival of an electrical signal (action potential) at the muscle fiber.

• The binding of myosin to actin.

• The movement of tropomyosin away from actin.

What causes an action potential to be generated in the postsynaptic neuron after neurotransmitter release?

• Binding of neurotransmitters opens sodium channels, leading to depolarization of the postsynaptic membrane.

• Neurotransmitters directly bind to voltage-gated calcium channels, causing an action potential.

• The reuptake of neurotransmitters into the presynaptic neuron triggers action potential generation.

• Neurotransmitters close potassium channels, causing hyperpolarization and action potential generation.

What is the term for the connection between a neuron and a muscle cell?

• Neuromuscular junction

• Dendrite

• Synapse

• Axon terminal

What is the overall process of muscle contraction initiated by electrical impulses called?

• Excitation-contraction coupling

• Muscle relaxation

• Neurotransmitter release

• Action potential generation