Answer:
Calcium ions
Step-by-step explanation:
This is because the contraction of skeletal muscle occurs as a result of the release of Calcium ions from internal stores which is a result of the function of a neural signal.
So, skeletal muscles contract when calcium ions are released. There is also an action potential which is generated which causes the muscle to contract. This action potential is present in both skeletal muscle cells and neurons and is as a result of the movement of sodium ions in neurons and calcium ions in skeletal muscle cells.