Topic 6.5 The Nervous System 0 IB Objectives Neurons transmit electrical impulses. The myelination of nerve fibers allows for saltatory conduction. Neurons pump sodium and potassium ions across their membranes to generate a resting potential An action potential consists of depolarization and repolarization of the neuron. Nerve impulses are action potentials propagated along the axons of neurons. Propagation of nerve impulses is the result of local currents that cause each successive part of the axon to reach the threshold potential. Synapses are junctions between neurons and between neurons and receptor or effector cells. When presynaptic neurons are depolarized they release a neurotransmitter into the synapse.