Answer: Nervous system
Explanation:
The skeletal and muscular system are the two inter-related systems in the body which ensures the movement of the body. The nervous system releases a chemical message through motor neuron, which is a neurotransmitter acetylcholine that binds to the receptors present outside the muscle fibers. These receptors ensures the movement of the muscles along with skeleton. The motor neuron ensures the contraction and relaxation of the muscles.
