Preganglionaariset

Preganglionaariset refers to nerve fibers that originate in the central nervous system and synapse with neurons in autonomic ganglia. These neurons are part of the autonomic nervous system, which controls involuntary bodily functions such as heart rate, digestion, and respiration.

There are two main divisions of the autonomic nervous system: the sympathetic nervous system and the parasympathetic nervous system. Preganglionic neurons are present in both divisions.

In the sympathetic nervous system, preganglionic neurons originate in the thoracic and lumbar regions of the spinal cord. Their axons extend to ganglia located near the spinal cord, such as the sympathetic chain ganglia or prevertebral ganglia.

In the parasympathetic nervous system, preganglionic neurons originate in the brainstem and the sacral region of the spinal cord. Their axons extend to ganglia that are typically located close to or within the walls of the target organs.

The neurotransmitter released by preganglionic neurons at the synapse with postganglionic neurons is almost always acetylcholine (ACh). This acetylcholine binds to nicotinic receptors on the postganglionic neuron, causing depolarization and the generation of an action potential. The postganglionic neuron then transmits the signal to the effector organ. The preganglionic fibers are generally myelinated, allowing for rapid transmission of signals. Their length can vary significantly depending on the division of the autonomic nervous system and the location of the ganglion.