What does the sliding filament model describe during muscle contraction?

• A. The breakdown of ATP into ADP and phosphate.
• B. The interaction between actin and myosin filaments leading to muscle shortening.
• C. The generation of electrical impulses in the motor neuron.
• D. The process of calcium ions being released from the sarcoplasmic reticulum.

Answer: (B)

Verified step by step guidance

1. Begin by understanding the sliding filament model, which is a fundamental concept in muscle physiology describing how muscles contract.
2. Recognize that muscle contraction involves the interaction between two types of protein filaments: actin and myosin.
3. During contraction, myosin heads bind to actin filaments, forming cross-bridges. This is powered by the hydrolysis of ATP into ADP and inorganic phosphate, which provides the energy for the myosin heads to pull the actin filaments inward.
4. This pulling action causes the sarcomere, the functional unit of a muscle fiber, to shorten, leading to overall muscle shortening and contraction.
5. Calcium ions play a crucial role by binding to troponin, which causes a conformational change in tropomyosin, exposing binding sites on actin for myosin, thus facilitating the sliding filament process.