chapter 36 - Vestibular Mechanics - KEMT FEI TUKE

everyday movement. Environments such as an aircraft flight can produce frequencies outside the linear
range for these transducers.
Rabbit and Damino [1992] have modeled the flow of endolymph in the ampulla and its interaction
with a cupula. This model indicates that the cupula in the mechanical system appears to add a highfrequency
gain enhancement as well as phase lead over previous mechanical models. This is consistent
with measurements of vestibular nerve recordings of gain and phase. Prior to this work this gain and
phase enhancement were thought to be of hair cell origin.
Defining Terms
Endolymph: Fluid similar to intercellular fluid (high in potassium) which fills the membranous labyrinth,
canals, utricle, and saccule.
Kelvin-Voight viscoelastic material: The simplest of solid materials which have both elastic and viscous
responses of deformation. The viscous and elastic responses appear to act in parallel.
Otolith: Linear accelerometers of the vestibular system whose primary transduced signal is the sum of
linear acceleration and gravity in the frequency range from DC (static) up to the maximum
experienced by an animal.
Semicircular canals: Angular motion sensors of the vestibular system whose primary transduced signal
is angular velocity in the frequency range of normal animal motion.
References
Grant JW, Best WA, Lonegro R. 1984. Governing equations of motion for the otolith organs and their
response to a step change in velocity of the skull. J Biomech Eng 106:203.
Grant JW, Cotton JR. 1991. A model for otolith dynamic response with a viscoelastic gel layer. J Vestibular
Res 1:139.
Grant JW, Huang CC, Cotton JR. 1994. Theoretical mechanical frequency response of the otolith organs.
J Vestibular Res 4(2):137.
Lewis ER, Leverens EL, Bialek WS. 1985. The Vertebrate Inner Ear, Boca Raton, Fla, CRC Press.
Rabbit RD, Damino ER. 1992. A hydroelastic model of macromachanics in the endolymphatic vestibular
canal. J Fluid Mech 238:337.
Van Buskirk WC. 1977. The effects of the utricle on flow in the semicircular canals. Ann Biomed Eng 5:1.
Van Buskirk WC, Grant JW. 1973. Biomechanics of the semicircular canals, pp 53–54, New York, Biomechanics
Symposium of American Society of Mechanical Engineers.
Van Buskirk WC, Grant JW. 1987. Vestibular mechanics. In R. Skalak, S. Chien (eds), Handbook of
Bioengineering, pp 31.1–31.17, New York, McGraw-Hill.
Van Buskirk WC, Watts RG, Liu YU. 1976. Fluid mechanics of the semicircular canal. J Fluid Mech 78:87.
Nomenclature
Otolith Variables
x = coordinate direction in the plane of the otoconial layer
y g = coordinate direction normal to the plane of the otolith with origin at the gel base
y f = coordinate direction normal to the plane of the otolith with origin at the fluid base
t = time
u(y f,t) = velocity of the endolymph fluid measured with respect to the skull
v(t) = velocity of the otoconial layer measured with respect to the skull
w(y g,t) = velocity of the gel layer measured with respect to the skull
δ g(y g,t) = displacement of the gel layer measured with respect to the skull
δ o = displacement of the otoconial layer measured with respect to the skull
V s = skull velocity in the x direction measured with respect to an inertial reference frame
V = a characteristic velocity of the skull in the problem (magnitude of a step change)
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