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Multiple Choice
According to the sliding filament model, which event occurs during muscle contraction?
A
Actin filaments slide past myosin filaments, shortening the sarcomere.
B
Myosin filaments shorten while actin filaments remain stationary.
C
Both actin and myosin filaments lengthen, causing the muscle to contract.
D
The sarcomere lengthens as actin and myosin filaments move apart.
Verified step by step guidance
1
Understand the sliding filament model: The sliding filament model explains how muscles contract by describing the interaction between actin and myosin filaments within the sarcomere, the functional unit of muscle fibers.
Identify the key components involved: Actin filaments are thin filaments, while myosin filaments are thick filaments. These filaments interact during muscle contraction, facilitated by ATP and calcium ions.
Focus on the mechanism: During contraction, myosin heads bind to actin filaments, forming cross-bridges. The myosin heads then pull the actin filaments toward the center of the sarcomere, causing the sarcomere to shorten.
Clarify the result of filament movement: Actin filaments slide past myosin filaments, but neither filament changes its length. The shortening of the sarcomere leads to overall muscle contraction.
Eliminate incorrect options: Myosin filaments do not shorten, actin filaments do not remain stationary, and the sarcomere does not lengthen during contraction. The correct event is the sliding of actin filaments past myosin filaments, shortening the sarcomere.