excitable cells Flashcards
conduction: define the term "regenerative" as applied to action potentials and explain the significance for conduction of the action potential, explain how conduction along the axon occurs, list structural features that effect the conduction velocity along normal axons and pathological conditions that may affect conduction
1
Q
define regenerative
A
self-supportive through positive feedback; all-or-nothing
2
Q
regenerative relationship between permeability of Na+ and membrane potential: all-or-nothing response
A
once threshold potential reached action potential triggered; all-or-nothing nature as cannot stop action potential forming; absolute refractory state as unresponsive to threshold depolarisation
3
Q
Na+ positive feedback during action potential
A
Na+ voltage-gated channels open → Na+ permeability increases → more Na+ into cell → more depolarisation cycle; continues until inactivated channels; refractory state until channels recover
4
Q
what slows conduction velocity
A
reduced axon diameter, reduced myelination (MS), cold anoxia, compression and drugs
