Neuromuscular function and transmission

Abstract

Understanding the biological processes and mechanisms underlying neuromuscular function in anaesthetized or sedated patients depends on adequate knowledge of the anatomy, physiology, and pathology of the connections between motor neurons and muscle fibres at neuromuscular junctions. Neuromuscular synaptic integrity depends on: maintenance of Ca²⁺-dependent release of acetylcholine by exocytosis from synaptic vesicles that fuse with active zones in motor nerve terminal membranes; the subsequent depolarizing action of acetylcholine on postsynaptic receptors at motor endplates; and termination of neuromuscular transmission by enzymic action of acetylcholinesterase located in the synaptic basal lamina. Homeostatic mechanisms sustain the magnitude of endplate potentials and the safety factor for neuromuscular transmission; but dysfunction of neuromuscular junctions occurs following administration of neuromuscular blockers or in diseases and other conditions affecting release, action and inactivation of acetylcholine.