Nerve impulse, illustration. Illustration of a nerve impulse transmitted from left to right. The impulse goes along the axon of (presynaptic) neuron A to the synapse of neuron A. The zoom shows the impulse travelling along the axon : the positive Na+ ions (red) enter the axon at the nodes of Ranvier, where the ion channels (blue) are located. This change in polarity creates an electric current that travels along the axon to the neuronal synapse. The impulse is transmitted from neuron A to (postsynaptic) neuron B at the gap junction. The vesicles at the neuron A synapse are filled with neurotransmitters (green triangles) which are released into the gap. The neurotransmitters bind to the channels (blue) at the dendrites of neuron B, opening the terminal boutons and letting the positive Na+ ions (red dots) in, thus creating an electric current.
