Final answer:
In myosin II, the tails are centrally located and intertwined, forming thick filaments, while the globular heads point outward, ready to interact with actin during the power stroke of muscle contraction. The heads pull actin filaments toward the M line, causing sarcomere shortening and muscle contraction.
Step-by-step explanation:
In myosin II, the tails point towards the center of the myosin filament and are intertwined with other myosin tails, creating the thick filament structure. The globular heads point outward and are responsible for the interaction with actin filaments during muscle contraction.
This conforms to the sliding filament theory of muscle contraction. When myosin II is in its 'bent' conformation, the myosin heads are energized by ATP and ready to bind to actin for another round of contraction, known as the power stroke.
During muscle contraction, myosin heads bind to actin at specific sites, forming cross-bridges. After undergoing a conformational change powered by the hydrolysis of ATP, the heads pull the actin filament towards the M line, moving the Z lines closer together, which shortens the sarcomere and ultimately causes the muscle to contract.
This process relies heavily on the polarity of actin filaments, where the myosin heads move towards the M line, suggesting the directionality of the muscle contraction mechanism.