Postganglionic neuron

Postganglionic neuron refers to the type of neuron that connects the autonomic nervous system (ANS) to the target organ. These neurons are part of the peripheral nervous system and follow the preganglionic neuron in the signal pathway from the brain or spinal cord to the body's tissues. The synapse between a preganglionic neuron and a postganglionic neuron occurs in an autonomic ganglion, where neurotransmitter release and receptor binding facilitate the transmission of impulses.

Structure and Function

Postganglionic neurons have their cell bodies located in either a paravertebral ganglia of the sympathetic nervous system or in the prevertebral ganglia and intramural ganglia of the parasympathetic nervous system. Unlike preganglionic neurons, which are myelinated, postganglionic neurons are unmyelinated, contributing to their grey appearance and sometimes being referred to as grey rami communications.

The primary neurotransmitter released by postganglionic fibers in the sympathetic nervous system is norepinephrine (noradrenaline), which binds to adrenergic receptors on the target organ. However, in the parasympathetic nervous system, the primary neurotransmitter is acetylcholine, which binds to muscarinic receptors. This difference in neurotransmitters is crucial for the diverse effects the sympathetic and parasympathetic nervous systems have on the body.

Clinical Significance

Abnormalities in postganglionic neuron function can lead to various clinical conditions. For example, damage to postganglionic sympathetic neurons can result in Horner's syndrome, characterized by ptosis (drooping eyelid), miosis (constricted pupil), and anhidrosis (lack of sweating) on the affected side of the face. Additionally, dysautonomia, a disorder of the autonomic nervous system, can involve dysfunction of postganglionic neurons, leading to symptoms such as orthostatic hypotension, tachycardia, and digestive disturbances.

Research and Applications

Research into postganglionic neurons has implications for understanding and treating autonomic nervous system disorders. For instance, novel therapies targeting the neurotransmitters and receptors involved in postganglionic signaling are being explored for conditions like hypertension and chronic pain.