Auditory Brain Stem
Outer ear, pinna to inner ear transduction to the brainstem auditory pathway for hearing. all of the important steps visually for one to be able to hear and the potential damage that can happen and signs and symptoms.
The Auditory System***Physics of sound, stucture of sound waves, physical dimension, psychological dimension; the dB (decibel), a log scale is a measure of sound pressure level. Behavior of sound waves in air is complex and involves pitch, tibral and echoic cues. Rarefacion and condensation waves use sound emitted by an object to extimate dparture and approach. Bone conduction and mechanico-hydraulic transduction are an early for of substrate-driven hearing. The cochlea is a hollow, fluid-filled tube (Reissner's membrane) within which the basilar membrane resides. Supports the hair cells, which are bathed in cochlear endolymph that is essential for their metabolic health and electrophysiological parformance. Reissner's membrane itself is bathed in perilymph, which cushions the membranous labyrinth from direct contact with the bony cochlea. Tympanic membrane is coupled to the ossicles of the middle ear and it represents the first site of airborne wavefront to tissue contact. The middle ear is responsible for the transformation of a pressure change to a mechanical displacement. The ossicles act as a series of levers to match the impedance of the tympanic membrane, which is large and resembles a drum head. The air borne vibrations displace perilymph which in turn transmits the waveforms to the endolymph and thus moves the hair cells apical tips creating a receptor potential. The structure of the basilar membrane is directly related to its mechanoelectrical performance. The hair cells, there are about 20,000***
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Auditory Brain Stem Response: Cochlea, VIIIth nerve, pons, midbrain, thalamus
sensitive to cochlear ischemia
very sensitive to stretch of the viiith facial nerve
acoustic neuroma, other skull base tumors
retraction of the cerebellum to expose other cranial nerves (microvascular decompression)
somewhat sensitive to upper brainstem ischemia
virtually immune to common agents
sensitive to cochlear ischemia
very sensitive to stretch of the viiith facial nerve
acoustic neuroma, other skull base tumors
retraction of the cerebellum to expose other cranial nerves (microvascular decompression)
somewhat sensitive to upper brainstem ischemia
virtually immune to common agents