CVS Practice Test 2025 – The All-In-One Guide to Exam Success!

During muscle contraction, the primary interaction occurs between actin and myosin filaments, which are essential components of the muscle fibers. Actin is a thin filament that provides the structural framework for muscle contraction, while myosin is a thick filament with ATPase activity that generates force.

When a muscle contracts, these two types of filaments slide past each other in a process known as the sliding filament theory. Myosin heads attach to specific binding sites on the actin filaments, forming cross-bridges. The energy derived from ATP hydrolysis powers the movement of the myosin heads, pulling the actin filaments inward, thus shortening the muscle fiber.

The other choices represent different proteins that serve distinct roles but are not directly involved in the sliding mechanism during muscle contraction. Collagen and elastin are structural proteins providing support and elasticity in connective tissues, while titin and nebulin are involved in muscle stability and organization rather than the contraction process itself. Keratin is a structural protein found in hair and nails, and myoglobin is a protein responsible for oxygen storage in muscle cells, neither of which play a role in filament sliding during contraction.