Final answer:
The termination of action of neuromuscular blockers is determined by the inhibition of acetylcholine release from the presynaptic terminal of motor neurons into the neuromuscular junction.
Step-by-step explanation:
The termination of action of neuromuscular blockers is determined by the inhibition of acetylcholine (ACh) release from the presynaptic terminal of motor neurons into the neuromuscular junction. When neuromuscular blockers like botulinum toxin or d-tubocurarine enter the bloodstream, they bind to the presynaptic membranes at the neuromuscular junction and prevent the release of ACh. This results in the loss of muscle activity, leading to muscle relaxation and paralysis.