What is the Origin of Parasympathetic Preganglionic Neurons?

The term is derived from the Greek para (beside) and sympathein (to feel with), describing the division of the autonomic nervous system that counterbalances the sympathetic system. "Preganglionic" indicates that these neurons are located before the ganglion, where they synapse with the second neuron in the pathway. This anatomical and functional classification is fundamental to neurophysiology and autonomic control.

What is the Mechanism of Parasympathetic Preganglionic Neurons?

The operational mechanism involves the release of acetylcholine (ACh) from the preganglionic axon terminal into the synaptic cleft of the autonomic ganglion. This ACh binds to nicotinic cholinergic receptors on the cell body of the postganglionic neuron, triggering an excitatory postsynaptic potential. The resulting action potential then travels along the shorter postganglionic axon to the effector organ, where ACh is again released, this time binding to muscarinic receptors to elicit the final, specific parasympathetic response.

Parasympathetic Preganglionic Neurons ∞ Area

Parasympathetic Preganglionic Neurons

Meaning

Parasympathetic preganglionic neurons are the efferent nerve cells of the parasympathetic division of the autonomic nervous system (PNS) whose cell bodies are located in the brainstem or the sacral spinal cord. These neurons extend long axons that travel to ganglia located near or within the wall of their target organs, such as the heart, lungs, or digestive tract. They release the neurotransmitter acetylcholine (ACh) onto the postganglionic neurons, initiating the “rest and digest” responses essential for conserving energy, slowing the heart rate, and promoting digestion.