What does summation refer to in muscle physiology?

What does summation refer to in muscle physiology?

• The process by which a muscle becomes fatigued after prolonged activity.

• The decrease in tension when a muscle is repeatedly stimulated.

• The repeated stimulation of a muscle that leads to an increase in tension compared to a single twitch.

• The complete relaxation of a muscle after a single twitch.

Answer explanation

Summation in muscle physiology refers to the repeated stimulation of a muscle that leads to an increase in tension compared to a single twitch.

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

• It stores the Ca++ 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 prevents the depolarization of the muscle membrane.

Answer explanation

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

What is the function of tropomyosin in muscle cells?

• It binds calcium ions to initiate muscle contraction.

• It covers the actin-binding sites to prevent the myosin cross-bridge from touching actin.

• It serves as the primary motor protein for muscle contraction.

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

Answer explanation

Tropomyosin covers the actin-binding sites to prevent 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 contraction.

What is a characteristic of Type I Fibers?

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

• They are primarily used for short, explosive movements.

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

• They have a low resistance to fatigue and are not suitable for endurance 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

• Satellite cell

• Actin filament

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 that contain contractile proteins in a muscle fiber?

• Myofibrils

• Sarcomeres

• Satellite cells

• Actin filaments

Answer explanation

Myofibrils are the threadlike structures that contain contractile proteins in a muscle fiber, making them the correct choice.

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

• Z line

• M line

• H zone

• Satellite cell

Answer explanation

The Satellite cell is NOT a component of a sarcomere. The other components are Z line, M line, and H zone.