Typically, voltage changes in neurons flow from dendrites, to the soma, and to the axon. In sensory neurons, however, environmental stimuli (light, chemicals, and pain) activate ion channels which produce action potentials that flow from the axon to the soma. In either case, neurons propagate signals along their axons in the form of action potentials, which is how neurons communicate with other neurons or cells. The communication that occurs between these cells is called synaptic transmission.