BI SC 004 Lecture Notes - Lecture 19: Neuromuscular Junction, Action Potential, Motor Neuron
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Action potential: rapid change along the length of the cell membrane that transmits a nerve impulse. Doing a wave at a football stadium. Have to be strong enough, all the way through the. Sodium gates open, letting na+ in muscle: whole thing contracts, or it doesn"t, depolarization occurs. Potassium gates open, letting k+ out: repolarization occurs. 70 mv: wave of depolarization/repolarization travels down the cell membrane. Where the neurons meet muscle cells: neuromuscular junction. A synapse lies between the 2 cell types. The synapse is a small gap between the: sending neuron (presynaptic membrane) Presynaptic membrane: receiving cell (postsynaptic membrane) Transmission is accomplished across this gap by a neurotransmitter: examples: Calcium ions enter the axon terminal: stimulate the synaptic vesicles to fuse with the presynaptic membrane. Neurotransmitters are released: diffuse across the synapse. At the end of the motor neuron: axon terminus. The axon terminus is filled with synaptic vesicles: contain:
