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Introduction

    Vestibular is a term derived from the name hall, located within the inner ear, composed of a bony structure called the labyrinth. Located in the temporal bone, and inside, membranous structures. A number of sensory structures in the vestibular system, which allow the body to remain in balance in stance as in moviment .^1,2,3

    The attitude control system is understood as a series of muscle contractions that occur appropriate, based on sensory information, to ensure the desired body position whenever a movement is performed by a human being, then being very important for a variety of daily activities from simple to complex. The older theories of postural control believed that control was achieved through a series of motor responses, the result of activity reflexive.⁴

    When we missed the steps in a dance about the pace, lost his balance and stumbled, lost the logical sequence of steps in a walk, all that is constituted by the momentary interruption in the integrated circuit of postural reflexes. These labyrinthine righting reflex act on the head, neck, body and opticians, are situated in the ventral midbrain, located opposite the third pair of nerves cranial.^2,5

    In the context of rehabilitation, therapeutic procedures seek to restore balance, stimulating and accelerating the natural mechanisms of compensation, allowing the individual to perform the most perfect possible moves that were wont to do before you come to vertigo. These procedures seek to compensate the disturbances of body balance through exercises repetitive stimulation labyrinthine.¹

    Despite all the descriptions of the issue of balance in body posture has been studied, mechanisms are still lacking concerning the postural assessment. Well, you see a guy suffer some kind of interference by changing the posture from the system for balance and hearing related to the vestibulocochlear nerve and inner ear, and the most common cases related labyrinthitis and even ringing in ears.³

    In this sense, this review aims to identify the main actions of the vestibular system in the control of body posture and balance.

Anatomical characteristics of the Vestibular System

    The body responsible for maintaining the overall balance is recognized as apparatus or vestibular system, located in the inner ear and consists of three components: a peripheral sensory system, a CPU and a response mechanism motor.⁶

    The peripheral system consists of a set of motion sensors that send information to the central nervous system, specifically the vestibular nuclear complex and the cerebellum on the head angular velocity, linear acceleration and head orientation with the axis gravitational.^2,7

    The CPU, comprising the nervous system receives and processes the signals and combines them with other sensory information to estimate the head orientation . The response of the central vestibular system is transmitted to the extraocular muscles and the spinal cord to prepare two important reflexes, the vestibulo-ocular reflex and vestibular-spinal reflex. The vestibular-ocular reflex by peripheral portion generates eye movements, which allow a clear view while the head is moving, while the vestibular-spinal reflex generates body motion compensation, to maintain head and postural stability, and thus preventing falls. The performance of these reflexes is monitored by the central nervous system and, when necessary, they are adjusted by a processor adaptative.⁸

    Such sensory components that help our balance is in various daily activities like walking, jumping and ride the bike.⁹ There is a line between the sensory systems including vision, proprioception beyond the vestibular system. Each one contributes a specific function, forming our spatial orientation . The vestibular system provides information about angular head accelerations (right, left, rotation) and linear body movements (forward, backward, upward, downward), the view is responsible for the rapid assimilation of body movement and the sense of depth. Already the proprioceptive system through the structures located in muscles, tendons, etc., provide information about the positioning of body parts in space.¹

    The receptors contained in the vestibular system are sensitive to any change in head position or direction of motion . The movement of the head excites them, and from this, nerve impulses are sent to the Central Nervous System with regard to this change of position. Any movement of the head causes a stimulation of the receptors in the vestibular apparatus, which transmits neural information to the cerebellum and the vestibular nuclei located in the brainstem. Furthermore, the vestibular nuclei send a message to the center and the oculomotor neurons of the spinal cord that control movement of the head and limbs. Therefore, the vestibular system controls the movements of the head and eyes during the exercises, maintaining balance and allowing the visual control of events movement.^{10, 8}

Human balance and posture

    By studying body posture automatically we are studying the system of balance, because we understand there is a relationship of dependency between both³ order to understand the complexity of body posture in order to be an integrated and simultaneous between posture and balance, we must also emphasize the righting reflex used for maintaining posture. On a conceptual basis, the balance is defined as a generic term that describes the dynamics of body posture to prevent falls, it related to inertial forces acting on the body.¹¹ is also important to describe the balance is classified into two types: Balance static, which refers to balance and posture, when it is not in motion, and dynamic balance, which is related to balance and posture in response to movements of rotation.²

    The balance body posture is also grounded in relations from the afferent (auditory pathways and the vestibular pathways) through the eighth pair of cranial nerves called the vestibulocochlear, related respectively with the balance and hearing, two key factors in working with issues postural .^2,5

    The vestibular system is the receptor organ of balance located in the inner ear and includes the saccule, the utricle and ducts semicirculares.² Besides all its complexity, balance, posture is also based on relationships from the vestibular and auditory afferent pathways through the cranial nerve vestibulocochlear (VIII pair), respectively related to the balance and hearing, two key factors to work on issues postural.³

    The correct posture is one where the individual in the standing position, requires little exertion of the muscles and ligaments to stay in this position, so that is facilitated matching static.¹²

    Posture relates to optimized position, maintained with spontaneous and automatic feature of a body in perfect harmony with the gravitational force and prone to spend the rest state for the state of movimento.¹³ The maintenance of postural stability is described as a phenomenon critical to our everyday lives. Even the simple act of staying upright, static, requiring a complex integration of multiple sensory information, decision-making processes, and motor programming. To most people, such complicated control processes can be taken for granted, working fairly well. Of course, not everyone has such capacidade.¹⁴ In standing position, approximately 25% of body weight is distributed to each heel and 25% for the head of the five metatarsals of each foot, at a ratio of about one part to the metatarsus and for 2.5 shares metatarsals II to V. Most of the tension in the longitudinal arch is supported by the plantar ligaments. Only about 15-20% of tension are supported by posterior tibial and peroneal muscles. When the body is on the tip of one foot, the arc voltage is increased four vezes.³ Therefore, the postural control system includes all components sensorimotor and musculoskeletal systems that are involved in maintaining or search for a particular position corporal.⁴

    The attitude control system must be able to adjust the balance in unstable situations, however, must be versatile enough to allow rapid initiation of movement. The most obvious task performed by the postural control system is the maintenance of bipedal stance, but this system also operates during movement of the floor, for example. Finally, the task of postural control system is to maintain the horizontal projection of the center of gravity of the individual within the base of support defined by the base of the foot during the stance static.¹⁵

Balance and vestibular

    Balance is a sensorimotor function and aims to stabilize the visual field and maintain posture is essential in ereta.16 spatial relationship between organism and environment. It is the most complex sensorimotor phenomenon, which prevents us from imbalance and falls to the ground, even when faced with static changes (such as body upright inside a moving bus). When there is any change in the vestibular system, balance body is compromised and symptoms such as dizziness arise.¹

    Symptoms arising from vestibular disorders, the most common is dizziness, manifesting with various features: nonspecific dizziness, vertigo single episode or recurrent, continuous and intermittent dizziness, nausea or dizziness positional or positioning, oscillopsia, vertigo associated with auditory symptoms, dizziness with postural imbalance and instability of gait between.¹⁷

    Dizziness is described as the feeling of change of body balance, which may be of a rotation (vertigo) or non-rotating (instability, oscillation, hesitations, etc.). Both types can be caused by vestibular disorders primary or secondary, which is possible to prove by examination vestibular.¹⁸

    Vertigo is the main type of Dizziness. Can be objective (egocentric), when the patient notices the objects to run on around him or subjective (eccentric) when the patient has the impression of turning on the environment.

    Vertigo is the most frequent symptom, five to 10% of the world presents, and one third of people may experience dizziness at some point in life.16
The most common type of vertigo is known as Benign Paroxysmal Positional Vertigo (BPPV), where there is a detachment of mineral crystals of the hair cells of the utricular otolithic organ, which then float freely in the posterior semicircular channel or adhere to the top of the canal.¹⁹ manifestations of BPPV complain of brief episodes of vertigo precipitated by rapid changes in head position, so that movements of the head to one side, usually when turning in bed, lie down or stand up, look up or bend down, provoke attacks of vertigo lasting several seconds, with no hearing and after an attack more intense, a feeling of imbalance may persist for hours. To the extent that the crystals are dissolved in the endolymph, the attacks cease in a few weeks or few months, but may recur and, in elderly patients, persistence.⁸

    The second most common cause of vertigo, with onset usually preceded by viral upper respiratory tract or gastrointestinal failure is sudden or vestibular neuronitis vestibular.6 The main symptom is an acute onset of rotational vertigo severe and protracted, exacerbated by head movement and associated with horizontal-rotatory spontaneous nystagmus that leads to healthy vestibular system, causing imbalances and postural náusea.8 Besides the abrupt loss of function of a maze and it is also known as acute unilateral vestibular disorders (idiopathic).⁶

    There are other boards manifestation of vertigo that are considered physiologic and may be characterized by nausea and malaise triggered by an acceleration body unfamiliar to the individual, such as experiences in various types of transport as car, ship, plane or train . The dizzying heights affects some people who, when in high places, manifesting a subjective instability of posture and locomotion associated with fear of falling and changes vegetatives.⁸

Therapeutic strategies and treatments

    The ability to repair and adaptation of the system is so remarkable that, after removing half of the peripheral vestibular system, through a unilateral vestibular nerve section, the observation of clinical evidence of vestibular dysfunction is often quite difficult. While the ability of central mechanisms using vision, proprioception, auditory and tactile stimulation, or cognitive knowledge about the imminent movement allows the vestibular responses are based on a set multimodal sensory and highly structured.⁸

    However, in some vestibular conditions, strategic situations should be taken to be given back to the individual quality of life. Vestibular rehabilitation is seen as a therapeutic option that is highlighted by the use of physiological mechanisms stimulating the vestibular system, through the patient gain confidence in performing the day-to-day, the good results achieved by not showing the possible effects side effects of drugs and the practicality with which it is made, can be achieved through specific exercises, exercises in applied mechanics and the vertiginous patient, too, and electrical stimulation in the cervical region paravertebral.^{17, 8} Importantly rehabilitation techniques vestibular deficits will depend mainly found on physical examination and otoneurological of vestibular disease and their stage presentation clinic.⁸

    Although many studies are required to state with certainty what the best and most efficient posture, 3 However, some factors are important to improve the balance of our body posture and posture, such as: Practice regular physical activity, stretching exercises and muscle relaxation, breathing exercises, massage therapy, make short journeys with walking blindfolded, starting first with one eye open and one closed, and after some time training with both closed, noting that such practices should always be performed in the company of a person, preferably holding hands, swinging exercises the upper and lower limbs, remembering that to swing the legs you must be supported.⁵

    The administration of medicinal substances for the treatment of vertigo and other forms of dizziness is also very valuable and often essential and can be used in all types of Dizziness, with the goal of therapy is the restoration of balance, with the decrease in static and dynamic postural instability and improved tolerability to movements performed daily by patients.¹⁷

    It is worth emphasizing the importance of the visual system in the maintenance of postural balance function, although results were not significant when comparing tests with eyes open and fechados.³ The author further points out that most scholars in the fields of neuro-anatomy, neurophysiology neurobiomecânica and mainly relate quite clearly in his studies of balance and maintain body balance posture, the importance of proprioceptive systems and environment to maintain body balance posture. Also mention the so-called "static position" has shown to be impossible because there is always a swing, which translates into a dynamic situation with essential and continuous adjustments to maintain the position balance.⁵

Responses of Vestibular System in postural control

    We still do not fully understand how humans control the balance in upright posture. Problems due to deficiency in the control of posture seriously afflict humans in various situations. Simply put, the task of postural control system is to maintain the horizontal projection of the center of gravity of the individual within the base of support defined by the base of the foot during the stance static.²⁰

    What is presented in the literature is that the control of posture requires a dynamic interaction between sensory information and motor action may also be influenced by variables such as mechanical base suporte.21 When there is any disturbance related to the vestibular system, some postural adjustments must occur so that the body can remain in balance. If the disturbance is unexpected postural control is achieved through mechanisms of compensatory postural adjustments and when this disturbance is caused by movements generated by the individual, the postural control is achieved through mechanisms of postural adjustments antecipatory.⁴

    The postural control are going to represets the complex challenge to the neuromuscular control system, being the most obvious task of postural control system is to maintain bipedal stance, generating a series of muscle contractions that produce moments of force on the joints the musculoskeletal system. The central nervous system then monitors and maintains the postura.20 It is important to mention that the static human posture is maintained by a central postural program assisted by various sensory modalities, especially those of vestibular, visual, muscular, cutaneous and interoceptive. Together, these systems interact to stabilize the posture representation and body.²²

Concluding remarks

    Discussions concerning the vestibular system and control of posture show us that the simultaneous relationships of these components should always be considered in the context the physiological and / or pathological. It is clear that the actions of the vestibular system in the control of body posture are directly interconnected. But we also have to consider the approach given the situations that require the body balance in both static as dynamic. Because this plays an important role in posture. Finally stands out the interference of some pathologies, such as dizziness and vertigo, which depending on the severity, needs care, the latter as both therapeutic regimens.

References

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