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Neurons are highly elaborate cells with axons that can reach up to one meter or more in length. Despite this feature, peripheral neurons can rapidly transduce signals from the CNS to target tissues through the propagation of action potentials followed by neurotransmitter release. Action potentials are characterized by a rapid depolarization of the membrane, which propagates along the axon.

Given the lengthy distance which action potentials must propagate, what is one way in which neurons have evolved to increase the speed of action potential propagation?


Different neuronal cell-types increase electrical resistance by increasing cross-sectional area of the axon shaft and/or allowing salutatory conduction due to myelination from supporting glial cells.


Different neuronal cell-types increase electrical resistance by increasing expression of voltage-gated sodium channels, which allows more rapid sodium influx during action potentials.


Phosphorylation of the $Na^+$/$K^+$ ATPase increases the rate of ion exchange downstream of the action potential, which exaggerates the gradient across the membrane, subsequently increasing the rate of ion flux during action potentials.


Depolarization of the plasma membrane causes opening of intracellular ryanodine receptors, allowing the release of calcium into the cytosol from intracellular stores. This increase in cytosolic calcium serves to further depolarize the plasma membrane during action potential propagation.

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