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Balance By: Kristie, Aoife, Sierra Sensory receptors Mechanoreceptors: receptors that respond to gross movements of the head that disturb the ear fluids surrounding the balance organs. Sensitive equilibrium receptors make the nervous system aware of the position and movements of the head. Without this balance is impossible The inner ear is the only part that focuses on balance. Internal Ear structure Osseous labyrinth: bony chambers located within temporal bone behind the eye socket. Has 3 subdivisions the cochlea, vestibule, and semicircular canals. The osseous labyrinth holds plasmalike fluid called perilymph, that has membranous labyrinth suspended in it. Suspended in membranous labyrinth is thick fluid called endolymph. Equilibrium Vestibular apparatus: the equilibrium receptors of the ear, divided into two arms- static equilibrium and dynamic equilibrium Static equilibrium: membrane sacs in vestibule that report on changes of position of the head in space (with gravity) when head is not moving, help keep head erect. Each macula has receptor “hair” cells in the otolithic hair membrane- a jellylike mass studded with otoliths- tiny stones made of calcium salts. As head moves, the otoliths roll with gravity change, which pull the hairs, which send impulses to the vestibular nerve to the cerebellum, saying where the head is in space. Equilibrium cont’d Dynamic equilibrium receptors are in the semicircular canals. They respond to angle changes and rotations of the head In the crista ampullaris, a receptor region, has hair cells and the cupula- a gelatinous cap When head moves, endolymph canal stays behind, cupula bends with body’s movement, which stimulates hair cells and sends impulses to the vestibular nerve to the cerebellum. When moving at a constant rate they stop sending impulses, but continue again when there is change Hearing and Equilibrium Deficits Vertigo: “An unsteadiness sensation when walking, rotary sensations, a sensation of being afloat on the air, feeling of a hollow space in the head” Some autonomic symptoms such as sweating, nausea, and vomiting are found to accompany vertigo attacks Nystagmus: when the eyes move about involuntarily. These symptoms and sensations can occur at different random times and last temporarily, or they can be persistent and last permanently. Hearing and Equilibrium Deficits cont’d The vertigo problem can be derived from the ear or the brain: If it comes from the EAR it is termed peripheral. Peripheral causes of vertigo include Meniere's Disease, ear trauma, labyrinthitis, and Vestibular Neuronitis If the problem comes from the brain, then it is called central. Central causes of vertigo include stroke/or tumor in the brainstem, multiple sclerosis, migraine, drugs (sedatives), panic or anxiety, and head trauma. Peripheral dizziness can be seen to be less severe of the two because it does not severely affect the brain. Hearing and Equilibrium Deficits cont’d Meniere’s Syndrome: The most common causes of the disease are still unknown Symptoms: Fluctuating hearing loss with distortion of sounds and difficulty with speech discrimination Ringing in the affected ear (tinnitus) Symptoms cont. A sense of the room spinning (vertigo) A cold sweat, nausea, and vomiting, or generalized weakness during the attack The episodes are unpredictable and usually last from 1 hour to a few hours, depending on the severity of the disease Recurrence of the attacks is a cardinal feature of Ménière disease. Typically the attacks are few, but the usual pattern of Ménière disease is increasing frequency and severity of the symptoms. The disease can be very disabling as the frequency and severity of the attacks increases.