Classification of Neurons

Unipolar Neuron

Found in sensory neurons of PNS, In a unipolar neuron or pseudounipolar neuron the dendrites and axon are continuous-basically fused-and the cell body lies off to one side. The longest axons of unipolar neurons carry motor commands from the spinal cord to small muscles that move the toes.

Bipolar Neurons

Found in special sensory organs (sight, smell, hearing). Found in olfactory bulb. Have two distinct processes-one dendrite (that branches extensively into dendritic branches at its distal tip) and one axon-with the cell body between the two. Bipolar neurons are rare.

Multipolar Neurons

Common in the CNS. Include all skeletal muscle motor neurons. Have two or more dendrites and a single axon. The longest axons of multipolar neurons carry motor commands from the spinal cord to small muscles that move the toes.

Motor Neurons

Efferent Neurons form the efferent division of the PNS. The half a million motor neurons carry instructions from the CNS to peripheral effectors in a peripheral tissue, organ, or organ system. Axons of these neurons that travel away from the CNS are called efferent fibers.

Interneuron

Located between sensory and motor neurons. The 20 billion or so interneurons (association neurons) outnumber all other types of neurons combined. Most are located within the brain and spinal cord, but some are in autonomic ganglia. The main functions of interneurons is integration-they distribute sensory information and coordinate motor activity.

Sensory Neurons

or afferent neurons, form the afferent divisions of the PNS. The cell bodies off sensory neurons are located in the peripheral sensory ganglia (A ganglion is a collection off neuron cell bodies in the PNS. Sensory Neurons are unipolar neurons whose processes known as afferent fibers extend between a sensory receptor and the CNS (they deliver information form sensory receptors to the spinal cord of brain).