Final answer:
Muscle contraction is initiated by calcium ions released from the sarcoplasmic reticulum, not by an influx of potassium ions; these calcium ions allow actin and myosin to form cross-bridges following the sliding filament theory. The statement is false.
Step-by-step explanation:
False, an influx of potassium ions is not responsible for the cross-linking of actin and myosin filaments.
Instead, muscle contraction begins with the neurotransmitter acetylcholine (ACh) triggering an action potential that causes sodium ions (Na+) to enter the muscle fiber, leading to the release of calcium ions (Ca2+) from the sarcoplasmic reticulum (SR).
The calcium ions then bind to troponin on the actin filaments, which, in the presence of ATP, allows myosin heads to form cross-bridges with actin and facilitates muscle contraction through the sliding filament theory. This process is also known as cross-bridge cycling.