Understanding Skeletal Muscle Structure

Which protein is primarily responsible for the thick filaments in a myofibril?

• Actin

• Myosin

• Troponin

• Tropomyosin

What is the name of the junction where a motor neuron communicates with a skeletal muscle fiber?

• Synaptic cleft

• Neuromuscular junction

• Sarcomere

• Myofibril

What is the basic repeating unit of a myofibril called?

• Sarcolemma

• Sarcomere

• Mitochondria

• Myosin head

Which of the following best describes the role of calcium ions in muscle contraction?

• They break down ATP for energy.

• They bind to troponin, allowing actin and myosin to interact.

• They form the thick filaments.

• They transmit nerve impulses.

During the sliding filament model, what happens to the length of the sarcomere as a muscle contracts?

• It increases

• It decreases

• It remains the same

• It disappears

Explain how the neurotransmitter acetylcholine initiates muscle contraction at the neuromuscular junction.

• It binds to receptors on the muscle fiber, causing sodium ions to enter and generate an action potential.

• It breaks down ATP, providing energy for contraction.

• It blocks calcium channels, preventing contraction.

• It binds to myosin, allowing it to attach to actin.