Préganglionares

Préganglionares refers to neurons in the autonomic nervous system whose cell bodies are located in the central nervous system and whose axons extend to the autonomic ganglia. These preganglionic neurons are crucial for transmitting signals from the brain and spinal cord to the peripheral nervous system.

In the sympathetic nervous system, preganglionic neurons originate in the thoracic and lumbar segments of the spinal cord. Their axons, which are typically thinly myelinated, exit the spinal cord via the ventral roots and travel to sympathetic ganglia, which are organized in two chains alongside the vertebral column, or in collateral ganglia located anterior to the vertebral column.

In the parasympathetic nervous system, preganglionic neurons originate in the brainstem (cranial nerves III, VII, IX, and X) and in the sacral segments of the spinal cord. Their axons are generally longer than those of sympathetic preganglionic neurons and travel directly to ganglia located near or within the walls of target organs.

The neurotransmitter released by preganglionic neurons at the synapse with postganglionic neurons in the autonomic ganglia is acetylcholine (ACh). This acetylcholine acts on nicotinic acetylcholine receptors on the postganglionic neurons, causing depolarization and the generation of an action potential that will then be transmitted to the effector organ. The preganglionic neurons are the first step in the efferent pathway of the autonomic reflex arc.