Information Transfer Across Chemical Synapse

step 1

nerve impulse reaches axon terminal containing synaptic vesicles with neurotransmitter inside each vesicle

step 2

Ca²⁺ gates open in presynaptic axon terminal and Ca²⁺ floods into terminal from extracellular fluid

step 3

Ca²⁺ acts as messenger instructing synaptic vesicles to fuse w/ axon membrane and empty in synaptic cleft (Ca²⁺ also leaves via Ca²⁺ pump or taken up by mitochondria)

step 4

neurotransmitter binds to postsynaptic protein receptors, they change shape, causing Na⁺ channels to open, an influx of Na⁺, and an AP

step 5

termination of neurotransmitter and AP

termination of neurotransmitter and AP can be:

• degradation by enzymes

• removal by astrocytes or post synaptic terminal, where then destroyed by enzymes

• natural diffusion away from synapse