PREGANGLIONIC FIBER Meaning and
Definition
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A preganglionic fiber refers to a nerve fiber that originates from a cell body in the central nervous system (CNS) and travels to a ganglion, which is a cluster of nerve cell bodies located outside the CNS. These fibers are part of the autonomic nervous system (ANS), which controls involuntary bodily functions, such as digestion, blood pressure, and heart rate.
Preganglionic fibers consist of two divisions within the ANS, namely the sympathetic and parasympathetic divisions. In the sympathetic division, the preganglionic fibers arise from the thoracic and lumbar regions of the spinal cord and form synapses with postganglionic fibers in paravertebral or prevertebral ganglia. The sympathetic preganglionic fibers are responsible for initiating the "fight or flight" response by increasing heart rate, dilating blood vessels, and mobilizing energy resources.
On the other hand, the parasympathetic division of the ANS involves preganglionic fibers originating in the cranial and sacral regions of the CNS. These fibers synapse with postganglionic neurons in peripheral ganglia that are located near or within the target organ. Parasympathetic preganglionic fibers are responsible for stimulating physiological processes that promote rest and digestion, including slowing down the heart rate, constricting blood vessels, and increasing gastrointestinal activity.
In summary, preganglionic fibers are key components of the autonomic nervous system, serving as the initial transmitters of signals from the CNS to peripheral ganglia. They play a crucial role in regulating various bodily functions, allowing for coordinated physiological responses in different situations.
Etymology of PREGANGLIONIC FIBER
The word "preganglionic fiber" is derived from several parts:
1. Pre-: This prefix comes from the Latin word "prae", meaning "before" or "in front of". In medical terminology, "pre-" is commonly used to indicate that something is situated before or prior to a particular structure or process.
2. Ganglion: This word derives from the Greek word "ganglion", meaning "knot" or "swelling". In anatomy, a ganglion refers to a cluster of neuronal cell bodies situated outside the central nervous system (CNS).
3. -ic: This suffix is commonly used in English to form adjectives. In this case, it serves to modify "fiber" and turn it into an adjective, indicating a characteristic or property of a fiber.
