Final answer:
Calcium ions binding to troponin lead to the exposure of myosin-binding sites on actin filaments, allowing muscle contraction through actin and myosin cross-bridge formation.
Step-by-step explanation:
When calcium ions (Ca2+) bind to troponin, this triggers a conformational change that moves tropomyosin away from the myosin-binding sites on actin filaments.
Once these sites are exposed, the myosin heads can bind to them, forming cross-bridges between the actin and myosin microfilaments, leading to muscle contraction.
In essence, Ca2+ influx is pivotal for actin and myosin interaction, which is a fundamental aspect of the muscle contraction cycle in striated muscles, including both skeletal and cardiac muscles, as well as a different role in smooth muscle contraction.