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Biomechanics of the Vestibular System:

A Numerical Simulation

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‡
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Carla F. Santos*, Jorge Belinha , Fernanda Gentil , Marco Parente ,
and Renato M. Natal Jorge*
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*Faculty of Engineering of University of Porto (FEUP), Porto, Portugal Institute of Science and Innovation in Mechanical
‡
and Industrial Engineering (INEGI), School of Engineering, Polytechnic of Porto (ISEP), Porto, Portugal School of
§
Health - P. Porto, Porto, Portugal INEGI, Institute of Mechanical Engineering and Industrial Management, Faculty of
Engineering of University of Porto, FEUP, Porto, Portugal

2.1 INTRODUCTION

The vestibular system is located in the posterior portion of the inner ear. It is a key component to our sense of balance
and movement. Any changes in this system can cause effects or symptoms such as dizziness, blurred vision, imbal-
ance, and nausea, which are vertiginous syndrome indicators. Vertigo is reported as one of the most common symp-
toms in the world [1]. It is considered the third most frequent complaint in medicine, transmitting a sense of
inadequacy and insecurity [2]. The main roles of the vestibular system, from a functional point of view, include
the correction of any involuntary movement of the body mass center and balance position to avoid falls; the accurate
perception of the body position in the environment and the perception of the direction and acceleration movements;
and the control of eye movement to maintain a clear visual field when the individual, the environment, or both are in
movement [3].
Gait and balance functions need the activation of three different sensory afferent systems, vestibular, visual, and
proprioceptive, which integrate the information and lead to body and view stabilization. A healthy and active lifestyle
demands a permanent stimulation of the vestibular system, which takes place during reactive adaptation, determining
a head position in the space relative to the fundamental posture, as in relation to the displacement [3, 4].
The static balance maintenance is a complex process, which has a vestibular intervention. The postural control system
results in the interaction between the input from the sensory system, the coordination of the central nervous system
(CNS), and the motor output. In this way, the sensory system provides information about the corporal position segment
in relation to other segments and the environment. These are transmitted and integrated with the CNS and sent to the
motor system, which is responsible for the correct and appropriate activation of muscles for movements [5, 6].
The interaction between the different sensory systems happens as a consequence of the stimulation of the vestibular
receptors by any head movement, which leads to a neural information transition to the cerebellum and the vestibular
nuclei located in the brain stem [5, 6].
The vestibular system nuclei send signals primarily to the neural central structures that control eye movements and
to the muscles that contribute to keeping an upright position. The projections to the former provide anatomical basis of
the vestibulo-ocular reflex (VOR), which is required for clear vision, and the projections to the muscles that control our
posture are necessary to keep us standing [4], maintain balance, and allow the visual control of motion events [3, 6].
Due to some vestibular disorders, characterized by dizziness symptoms triggered by some head positions (posi-
tional vertigo) or during the movement to one specific position of the cephalic segment (positioning vertigo), there

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