Muscle Contraction: The Sliding Filament Theory

What are the two main types of filaments involved in muscle contraction?

• Actin and myosin

• Keratin and elastin

• Collagen and fibrin

• Tubulin and desmin

According to the sliding filament theory, what happens to the sarcomeres during muscle contraction?

• They lengthen

• They shorten

• They remain the same length

• They disappear

What triggers the release of calcium ions in muscle fibers?

• A nerve impulse stimulates the muscle fibers.

• The presence of oxygen in the blood.

• An increase in body temperature.

• The absorption of glucose by the muscle.

Read the passage 'Muscle Contraction: The Sliding Filament Theory.' True or False: ATP is required for the myosin heads to detach from the actin filaments.

• True

• False

What is the role of calcium ions in muscle contraction?

• Calcium ions bind to troponin units on the actin myofilaments, displacing tropomyosin and exposing the myosin binding sites on the actin.

• Calcium ions provide energy for the contraction by hydrolyzing ATP.

• Calcium ions directly cause the shortening of the myosin filaments.

• Calcium ions inhibit the release of neurotransmitters at the neuromuscular junction.

Explain the importance of ATP in the process of muscle contraction and relaxation.

• ATP provides the energy for myosin heads to detach from actin and prepares them for the next contraction cycle.

• ATP acts as a neurotransmitter at the neuromuscular junction.

• ATP is responsible for generating action potentials in muscle fibers.

• ATP directly causes the release of calcium ions from the sarcoplasmic reticulum.

___are thin filaments.

• troponin

• tropomyosin

• actin

• myosin

___are thick filaments.

• actin

• myosin

• troponin

• tropomyosin

___are regulatory proteins that cover the myosin binding site on the actin.

• troponin-tropomyosin

• sarcomere

• sarcolemma

• sarcoplasmic reticulum

Calcium binds to ___of the troponin-tropomyosin complex.

• troponin

• tropomyosin

• actin

• myosin