Vestibular Receptor Cells

• An epithelium lines the inner surface of the membranous labyrinth of the auditory and vestibular systems. The sensory epithelium consists of patches (maculae or cristae) of receptor cells. The entire epithelium is supported on basement membrane that lines the inner surface of the labyrinth. Receptor cells are held away from the basement membrane by supporting cells but are joined to the supporting cells at the endolymph surface.

• Desmosomes join the lining cells as well as receptor cells to form a barrier between the labyrinthine surface and the intra-epithelium space across which ionic mechanisms operate.

• Teledendria of cranial nerve ganglia synapse on the base of the receptor cells. Transmitter in synaptic vesicles accumulates around dense bodies at the base of the receptor cell. A spherical or rod like-body stands over synaptic sites and acts to draw synaptic vesicles to the synaptic site. Axonal boutons do not require this mechanism because their volume is small as compared to the receptor cell.

• Efferent axons with transmitter vesicles arise from neurons in the brainstem to synapse on the receptor cells. See vestibular system for description of mechanisms.