Action potential An action potential is a spike of both positive and negative ionic discharge that travels along the membrane of a cell. The creation and conduction of action potentials represents a fundamental means of communication in the nervous system. Action potentials represent rapid reversals in voltage across the plasma membrane of axons. These rapid reversals are mediated by voltage-gated ion channels found in the plasma membrane. The action potential travels from one location in the cell to another, but ion flow across the membrane occurs only at the<unk> . As a result, the action potential signal jumps along the axon, from<unk>  to<unk> , rather than propagating smoothly, as they do in axons that lack a myelin sheath. The clustering of voltage-gated sodium and potassium ion channels at the<unk> s permits this behavior. Saltatory conduction Since an axon can be unmyelinated or myelinated, the action potential has two methods to travel down the axon. These methods are referred to as continuous conduction for unmyelinated axons, and saltatory conduction for myelinated axons. Saltatory conduction is defined as an action potential moving in discrete jumps down a myelinated axon. This process is outlined as the charge passively spreading to the next<unk>  to depolarize it to threshold which will then trigger an action potential in this region which will then passively spread to the next<unk>  and so on. Saltatory conduction provides one advantage over conduction that occurs along an axon without myelin sheaths. This is that the increased speed afforded by this mode of conduction assures faster interaction between neurons. On the other hand, depending on the average firing rate of the neuron, calculations show that the energetic cost of maintaining the resting potential of oligodendrocytes can outweigh the energy savings of action potentials. So, axon myelination does not necessarily save energy.
Node of Ranvier
Sarcoplasmic reticulum
Projection fiber
External limiting membrane
Neuroeffector junction
Internal limiting membrane
Neuromere
Basal dendrite