Function of the Transverse Tubule in Muscle Cells

What is the function of the transverse tubule in muscle cells?

• It stores the Ca²⁺ needed for muscle contraction.

• It conducts the action potential into the muscle to depolarize the terminal cisternae.

• It produces the action potential necessary for muscle contraction.

• It connects muscle cells to bone.

Answer explanation

The transverse tubule conducts the action potential into the muscle to depolarize the terminal cisternae, triggering muscle contraction.

What is the function of tropomyosin in muscle cells?

• It is an energy source for muscle contraction.

• It covers the actin-binding sites and prevents the myosin cross-bridge from touching actin.

• It facilitates the binding of myosin to actin.

• It breaks down ATP to release energy.

Answer explanation

Tropomyosin covers the actin-binding sites and prevents the myosin cross-bridge from touching actin, regulating muscle contraction.

What is the role of troponin in muscle contraction?

• It prevents the myosin cross-bridge from touching actin.

• It binds to calcium and initiates the movement of tropomyosin on actin to allow the myosin cross-bridge to touch actin and initiate contraction.

• It breaks down ATP to provide energy for muscle contraction.

• It synthesizes protein to strengthen muscle fibers.

Answer explanation

Troponin binds to calcium and initiates the movement of tropomyosin on actin to allow the myosin cross-bridge to touch actin and initiate muscle contraction.

What is a characteristic of Type I Fibers?

• They contain a small number of oxidative enzymes and are easily fatigued.

• They contain large numbers of oxidative enzymes and are highly fatigue resistant.

• They are primarily used for short, explosive movements.

• They have a low resistance to fatigue and are used for short-duration activities.

Answer explanation

Type I fibers contain large numbers of oxidative enzymes, making them highly fatigue resistant.

What is a characteristic of Type IIx fibers?

• They have a high number of mitochondria.

• They have a high capacity for aerobic metabolism.

• They are more resistant to fatigue than slow fibers.

• They have a relatively small number of mitochondria.

Answer explanation

Type IIx fibers have a relatively small number of mitochondria, distinguishing them from other fiber types.

What are the undifferentiated cells that are predicted to play a key role in muscle growth and repair called?

• Myofibril

• Sarcomere

• Satellite cell

• Actin filament

Answer explanation

Satellite cells are undifferentiated cells that are predicted to play a key role in muscle growth and repair.

What is the repeating unit within a skeletal muscle fiber called?

• Myofibril

• Sarcomere

• Z line

• H zone

Answer explanation

The repeating unit within a skeletal muscle fiber is called a sarcomere, which is responsible for muscle contraction and relaxation.

What are the threadlike structures in muscle fibers that contain contractile proteins?

• Myofibrils

• Sarcomeres

• Satellite cells

• Actin filaments

Answer explanation

Myofibrils are the threadlike structures in muscle fibers that contain contractile proteins, making them the correct choice for this question.

Which of the following is NOT a component of a sarcomere?

• A band

• I band

• M line

• Satellite cell

Answer explanation

The correct choice is Satellite cell as it is not a component of a sarcomere. A band, I band, and M line are all components of a sarcomere.

What are the two types of filaments found in the sarcomeres of skeletal muscle fibers?

• Myosin and actin

• Actin and satellite

• Myofibril and sarcomere

• Myosin and myofibril

Answer explanation

The two types of filaments found in the sarcomeres of skeletal muscle fibers are myosin and actin.