PREGANGLIONIC NEURONS Meaning and
Definition
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Preganglionic neurons are a type of nerve cell found in the autonomic nervous system (ANS) that serve as the initial components of the autonomic motor pathway. These neurons are responsible for conveying signals from the central nervous system (CNS), specifically the brain and spinal cord, to the ganglia.
The autonomic nervous system is divided into two main branches: the sympathetic and parasympathetic. Preganglionic neurons are present in both branches, but their location may differ depending on the division. In the parasympathetic division, preganglionic neurons are found within the brainstem and sacral region of the spinal cord, whereas in the sympathetic division, they are located in the thoracic and upper lumbar regions of the spinal cord.
These neurons transmit signals via long, myelinated axons that extend from the CNS to the ganglia, where they synapse with postganglionic neurons. The ganglia function as relay stations, where the preganglionic neuron communicates with the postganglionic neuron, which then carries the signal to the target organ or tissue.
Preganglionic neurons play a crucial role in coordinating and controlling involuntary bodily functions such as heart rate, digestion, glandular secretions, and pupil dilation. By receiving input from higher brain regions, preganglionic neurons shape the autonomic response according to the body's needs and various external stimuli.
Overall, preganglionic neurons are essential for the proper functioning of the autonomic nervous system, enabling the regulation of vital physiological processes necessary for maintaining homeostasis in the body.
Etymology of PREGANGLIONIC NEURONS
The word "preganglionic" is formed by the combination of two components: "pre-" and "ganglionic".
1. "Pre-" is a prefix derived from the Latin word "prae" meaning "before" or "in advance". It is commonly used as a prefix to indicate something that comes before or precedes something else.
2. "Ganglionic" is an adjective derived from the noun "ganglion", which is borrowed from the Greek word "ganglion", meaning "a swelling" or "a knot". In anatomy, a "ganglion" refers to a mass of nerve cell bodies located outside the central nervous system, typically forming a bulge along a nerve.
Hence, "preganglionic" refers to the neurons that are situated or acting before or in advance of the ganglia.
