PHYSIOL 1 Lecture Notes - Lecture 2: Neuromuscular Junction, Nicotinic Acetylcholine Receptor, Axon Terminal
Document Summary
Soma lives in ventral part of spinal cord. Each muscle fiber is innervated; stimulated to contract by one branch of one alpha-motorneuorn. Each neuron could influence multiple muscle fibers (simultaneously) Can"t talk about innervation without talking about motor units. One alpha-motorneuron and all of the muscle fibers it innervates; nerve muscle functional unit. As an ap moves toward axon terminals, ap gets depol. Alpha-mn is depol by some synaptic input, ap generated in alpha-mn. Once ap arrives at axon terminal(s), vg ca2+ channels open; ca2+ enters the cell. Vesicles filled with ach fuse with pre-synaptic membrane; ach enters synaptic cleft. Ach binds to nicotinic receptors on junctional folds of sarcolemma. Ach is quickly cleared from cleft (diffusion of ache) Resting em in fibers is almost equal to ek. After ach binds to nicotinic receptors, permeability to cations increases 1000-fold. Much stronger/greater amplitude than standard neural epsp. Na+ influx, depolarizes sarcolemma (motor end plate opens up vg na+; initiate.
