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Inner Ear Hair Cell Bundle Mechanics
Published in Joseph D. Bronzino, Donald R. Peterson, Biomedical Engineering Fundamentals, 2019
Hair cells are the sensory receptors in the inner ear. Auditory hair cells in the cochlea detect pressure waves to mediate hearing. Vestibular hair cells in semicircular canals, utricule, and saccule detect head movement and orientation. e hair cells are named so because of their characteristic structure at the apical surface of the cell called the hair bundle (see Figure 25.1). Mechanical stimuli such as sound pressure, acceleration, or gravity arrive through the extracellular structure at the hair bundle where it is turned into neural spike-train signals. How dierent mechanical stimuli are captured, ampli-ed, and encoded by hair cells is an important question in the inner ear science. e hair bundles have sophisticated structure and characteristic shapes depending on dierent inner ear organs (Figure 25.1). Even within the same sensory organ, the hair bundle shapes vary considerably and systematically. Considering such diverse and systematically arranged bundle shapes, it is logical to assume that the hair bundle mechanics play a crucial role on the hair cell’s function.
Physical Motion
Published in Alfred T. Lee, Vehicle Simulation, 2017
For linear acceleration and gravity sensing, the vestibular systems also contain the otolith organ, which is composed of two membranous sacs: the saccule and the utricle. Hair cells embedded within calcium carbonate inside these sacs are triggered when linear accelerations are applied to the head. As the saccule and utricle are oriented at 90° to one another, they respond to vertical (saccule) and horizontal (utricle) linear accelerations independently. Although the semicircular canals rely on physical movement, the otolith functions as both a dynamic and a static system. The gravity sensing component of the otolith is the principal means by which we sense the earth vertical. The process is occurring even when the head is not moved. When aligned with the earth-vertical axis, gravitational forces apply a shearing action on the otolith and this, in turn, sends signals to the brain that the head is upright. As the head is moved away from the vertical axis, signals are sent to the brain to automatically correct for this deviation, that is, to regain postural stability. Lateral and longitudinal acceleration of the head, as well as vertical accelerations, affect the otolith and these forces play an important role not only in postural stability, but also in how a vehicle operator responds to forces resulting from operator control inputs or from disturbances external to the vehicle.
Chapter 3 Physics of the Senses
Published in B H Brown, R H Smallwood, D C Barber, P V Lawford, D R Hose, Medical Physics and Biomedical Engineering, 2017
The inner ear (see figure 3.12) is a multi-chambered cavity in the temporal bone of the skull. It is said that it is the best protected of the organs associated with the sense. It consists of several parts, including the cochlea, the saccule, the utricle and the semi-circular canals. The function of the saccules is not known, and functions of the utricle and semi-circular canals are associated with our senses of position and balance. Only the cochlea has a role in the hearing process. The role of the cochlea is to convert the mechanical energy presented as a mechanical vibration at the oval window into electrical energy, transmitted onwards through the auditory nerve. We can study the anatomy of the cochlea and can thus gain some clues as to how this energy conversion might occur.
Smart platform for the analysis of cupula deformation caused by otoconia presence within SCCs
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
Radun Vulović, Milica Nikolić, Nenad Filipović
The vestibular apparatus together with cochlea make inner ear. Translational motion is regulated by the utricle and saccule placed within the vestibule. Utricle is a sort of fluid chamber, placed in vestibule and in front of the semicircular canals, containing the membrane as well. The utricle detects linear accelerations and head-tilts in the horizontal plane. The saccule detects linear accelerations and head tilts in the vertical plane. Rotational movements are detected by three semicircular canals for each ear, filled with fluid (Figure 1).