The peripheral auditory apparatus

Abstract

This review of the peripheral auditory apparatus represents an attempt to analyse critically recent developments in the field. The coverage is not exhaustive, the emphasis is on functional aspects and no attempt is made to review the anatomy of the ear. Particular emphasis is placed on three broad sections: the physiology of the middle ear, basilar membrane mechanics and the electrophysiology of the cochlea. It is in these areas that recent technical advances have led to experiments which throw doubt on traditionally held concepts. Such an advance is the application of the Mössbauer technique to the problem of middle- and inner-ear mechanics. Because of its novelty, this technique is discussed in detail. Other new methods such as laser holography are just starting to be used, as are the ion selective microelectrodes for measuring dynamic changes in endolymph concentration. After many years of slow progress there is a sudden spark of enthusiasm for peripheral auditory research, and the coming decade promises to be most exciting indeed.

Development of wide-band middle ear transmission in the Mongolian gerbil

“…Nearly three decades ago, Johnstone and Sellick (Johnstone and Sellick, 1972) marshalled convincing evidence against the then prevailing view (e.g., Dallos, 1973;Møller, 1963Møller, , 1965Mundie, 1963;Zwislocki, 1962Zwislocki, , 1963 that mass is the principal determinant of ossicular vibrations at high frequencies (see also Manley and Johnstone, 1974). Nevertheless, several subsequent discussions of middle-ear function have reiterated the mass-reactance hypothesis (e.g., Doan et al, 1996;Hemilä et al, 1995Hemilä et al, , 2001Nummela, 1997;Relkin, 1988;Relkin and Saunders, 1980;Shaw, 1981).…”

Resonant tectorial membrane motion in the inner ear: its crucial role in frequency tuning.

“…2A. Second, the phase response in the transverse direction is no longer shallow and becomes consistent with traveling-wave motion (41 The major problem with the isolated temporal bone preparation is that the endocochlear potential was -0 mV, meaning that the electrical drive to the hair cells was about half of its normal in vivo value (48,49). The absence of an endocochlear potential might explain the linearity of the responses (50).…”

Effects of cholera toxin on cochlear endolymph production: model for endolymphatic hydrops.

“…They were deprived of food but not water for [11][12][13][14][15][16][17][18] hr prior to study. They were anesthetized with an intraperitoneal injection of DIAL with urethane (0.9 g/kg of body weight).…”

“…By a direct stimulatory action on adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1], cholera toxin produces secretion of isotonic fluid by the gut (11), the action being mimicked by agents that increase cellular cyclic AMP concentrations. Although the molecular mechanisms for fluid absorption and secretion are not known, it has been demonstrated that cyclic AMP can alter membrane permeability (2, 12) as well as membrane electrolyte secretion (4, 7).The stria vascularis is assumed to be the epithelia membrane responsible for the maintenance of the endolymphatic potential (EP) and endolymph secretion into the scala media of the cochlea (13,14).The present study was performed to demonstrate the presence and possible role of cyclic AMP in the stria vascularis by stimulating intracochlear adenylate cyclase with purified cholera toxin. The toxin had a significant effect on endolymph production, although it did not alter either endolymphatic potential or electrolyte composition.…”

“…The stria vascularis is assumed to be the epithelia membrane responsible for the maintenance of the endolymphatic potential (EP) and endolymph secretion into the scala media of the cochlea (13,14).…”