Final answer:
The major intersection between the muscular and nervous system is at the neuromuscular junction, where acetylcholine released from motor neurons initiates muscle contraction.
Step-by-step explanation:
The major intersection between the muscular system and the nervous system is at the neuromuscular junction (NMJ). Motor neuron axons connect to muscle fibers at the NMJ, forming a specialized synaptic structure. The synaptic end bulbs of motor neurons release a neurotransmitter called acetylcholine, which binds to receptors on the muscle fiber sarcolemma. This binding opens ligand-gated ion channels and results in the depolarization of the sarcolemma, ultimately leading to muscle contraction. A motor unit comprises one motor neuron and all the muscle fibers it innervates. The interaction between neurons and muscles at the NMJ is essential for generating the muscular movements that are part of our daily activities.