Innervation of the Carotid Body
The carotid nerve consists mainly of fibers from the glossopharyngeal nerve and also receives 2 branches from the superior cervical ganglion, 1 of which runs around the glomus to enter the carotid nerve (Eyzaguirre and Uchizono, 1961). On cross section, it contains mainly myelinated (A) fibers 1 to 9 µm in diameter with a few nonmyelinated (C) fibers 0.1 to 0.2 µm in diameter. The myelinated (A) fibers, estimated at 600 to 700 (Eyzaguirre and Uchizono, 1961), represent the chemoreceptor and baroreceptor afferents of the glossopharyngeal nerve. They have conduction velocities of 4 to 53 m/s, with a median of 16 m/s (Fidone and Sato, 1969). In a study of single fibers, at least 61% were considered to be chemoreceptors (sensitive to high CO2 and low oxygen, with a short latency of response to cyanide and acetylcholine), and the remainder baroreceptor (having pulse-synchronous discharge and low threshold to mechanical stimuli) (Fidone and Sato, 1969).
KeywordsCarotid Body Superior Cervical Ganglion Chief Cell Sympathetic Fiber Glomus Cell
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