Which type of neuron is absent in the peripheral nervous system?

The peripheral nervous system contains afferent sensory neurons that propagate action potentials to the CNS via electrochemical junctures called synapses, using Neuro transmitters as chemical messengers.

The peripheral nervous system also contains efferent motor neurones that propagate action potentials away from the CNS towards effectors (skeletal muscle, smooth muscle, cardiac muscle, and glands) to stimulate them and induce a response. Skeletal muscles are stimulated via the somatic nervous system, whereas cardiac muscle, smooth muscle and glands are stimulated via the autonomic nervous system. The somatic and autonomic nervous system are the two subdivisions of the peripheral nervous system.

The peripheral nervous system does not contain relay neurones, which reside in the central nervous system (brain, spinal cord, and retina) and transfer electrical information that has entered from the sensory neurons of the dorsal root ganglia to the motor neurones of the ventral route ganglia so that the effectors can be stimulated.

The peripheral nervous system also contains the various dogiel cells (multipolar neurones) and supporting cells (similar to astrocytes in the brain) of the enteric nervous system.

Reference: Charlie Phaure