Final answer:
The contractile unit of muscle is called a sarcomere. In a muscle contraction, the thick and thin filaments slide past each other, causing the sarcomere to shorten. The sliding filament mechanism refers to this process.
Step-by-step explanation:
The contractile unit of muscle is called a sarcomere, which is made up of thick and thin filaments.
In a muscle contraction, the thick and thin filaments slide past each other, causing the sarcomere to shorten. The myosin filaments pull the actin filaments closer together, which in turn shortens the sarcomere.
The "sliding filament mechanism" refers to the process by which the thick and thin filaments slide past each other and generate filament movement, resulting in muscle contraction.