Why are action potentials usually conducted in one direction?
(A) lons can flow along the axon in only one direction.
(B) The brief refractory period prevents reopening of voltage-gated
[tex]\mathrm{Na}^{+}[/tex]channels.
(C) The axon hillock has a higher membrane potential than the terminals of the axon.
(D) Voltage-gated channels for both [tex]\mathrm{Na}^{\wedge}+[/tex] and [tex]\mathrm{K}^{+}[/tex]open in only one direction.
