They differ by the presence of dendrites and axons and also by specialized structures called synapses and chemicals such as neurotransmitters. Because the dorsal horn neuron is unipolar, actually pseudounipolar, it contains two axons rather than one axon and one dendrite. The axon may or may not be covered with myelin, a substance that acts as an insulator and increases the velocity of nerve impulses as they travel down the axon. This myelin sheath contains gaps called nodes of Ranvier, where axons are capable of branching. Dendrites are covered by processes called synapses.
Associational neurons carry impulses from neuron to neuron, meaning sensory to motor.
Motor neurons carry impulses away from the brain and spinal cord and out into the periphery. In order for this to happen, there must be a way for nerve impulses to get from one neuron to the next. This is accomplished by a synapse, which is a small gap between neurons. Transmission across the synapse occurs by chemical conduction. Neurotransmitters are the chemicals responsible for this travel.