Preganglionic

Preganglionic fibers are the nerve fibers that originate in the central nervous system and extend to the autonomic ganglia. They are part of the autonomic nervous system, which controls involuntary body functions such as heart rate, digestion, and respiratory rate.

Preganglionic fibers can be either sympathetic or parasympathetic, depending on their origin and function. Sympathetic preganglionic fibers originate in the thoracic and lumbar regions of the spinal cord, while parasympathetic preganglionic fibers originate in the brainstem and sacral region of the spinal cord.

Function

Preganglionic fibers transmit signals from the central nervous system to the autonomic ganglia. These signals are then relayed to the target organs by the postganglionic fibers. The type of signal transmitted by the preganglionic fiber determines whether the target organ's activity will be increased (sympathetic) or decreased (parasympathetic).

Structure

Preganglionic fibers are myelinated, which means they are covered in a layer of myelin. This allows for faster transmission of signals compared to unmyelinated fibers. The fibers connect the central nervous system to the autonomic ganglia, where they synapse with postganglionic neurons.

Clinical significance

Damage to preganglionic fibers can result in a variety of symptoms, depending on the specific fibers affected. For example, damage to sympathetic preganglionic fibers can result in decreased heart rate and blood pressure, while damage to parasympathetic preganglionic fibers can result in increased heart rate and blood pressure.

See also

• Postganglionic fiber
• Autonomic nervous system
• Sympathetic nervous system
• Parasympathetic nervous system

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