have voltage-reg. gates along the entire axolemma
when APs occur at the trigger zone:
Na+ enters and diffuses to adjacent areas
opening voltage gates just distal to the AP
Na+ and K+ gates open and close as at the trigger zone
this excites the membrane just distally
chain reaction travels to the end of the axon
relatively slow in unmyelinated axons
voltage-reg. gates are scarce in the internodes
400 times more at the nodes
Na+ cant diffuse anyway due to myelin sheath
so the APs jump from node to node:
transmit the signal much faster
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