Question

The release of ________ to muscle cell receptors triggers muscle contractions. ach serotonin dopamine adrenaline

Answer 1

The given blank can be filled with acetylcholine.  

Acetylcholine refers to a chemical messenger, that is, a neurotransmitter, discharged by the nerve cells in various segments of the peripheral nervous system. It monitors the contraction of all the voluntary muscles, like skeletal muscles. It also influences the contraction of the cardiac and smooth muscle.