Final answer:
The kinetic chain refers to the interconnected functioning of the Muscular system, Skeletal system, and Nervous system, with muscles moving the lever-like bones through contractions initiated by neural signals.
Step-by-step explanation:
The three systems that are collectively referred to as the kinetic chain are the Muscular system, Skeletal system, and Nervous system. Muscles cannot move the body on their own; they require the framework of the skeletal system to act upon. Skeletal muscles are attached to the bones by tendons, spanning joints and enabling movement when they contract. The skeleton provides a lever system, and the muscles apply the force needed to move these levers. Additionally, muscle contraction is dependent on neural input from the nervous system, where the spinal cord and other parts, like the somatic nervous system, play a crucial role in movement and coordination.
The introduction of neuromuscular junctions, resembling synapses between neurons, is significant in muscle contraction. This coordination illustrates how the nervous system influences the musculoskeletal system, emphasizing the connection for AP Courses in terms of understanding movement in biology.