Balance hair cells

Hair cells are the sensory cells of the auditory and vestibular systems. Hair cells are the sensory cells of the internal ear, essential for the senses of sound and balance. The hair cell s transduction apparatus, the molecular machinery that converts forces and displacements into electrical responses, can respond to mechanical stimuli of less than 1 nm in amplitude, and of tens or even hundreds of kilohertz in frequency. Indeed, our hearing is ultimately limited by Brownian motion of water molecules impinging on the transduction apparatus. 

The surprise is that genes clearly involved in mechano-transduction have not yet been identified by the deafness-gene approach. Clearly disruption of hair-cell function at many levels can lead to deafness, so it is expected that deafness genes include those involved in inner-ear development, in ion balance in the endolymph, and in structural integrity of hair cells. Examination of deafness genes in zebrafish has been particularly thorough, however, and... 

Other sets of hair cells are formed in specialized parts of the inner ear.964 The three semicircular canals detect angular acceleration in three directions, while the sac-like utricle and saccule detect linear acceleration including gravitational attraction. These two organs each contain a patch of hair cells whose tips project into a gelatinous layer, which is overlain by a field of small crystals of calcium carbonate. These little stones (otoliths) provide an inertial mass, which resists movement causing the hair cell tips to bend and activate mechanoreceptors to send information about balance and orientation to the brain. 

With the high concentrations achieved in attempted suicide, tinnitus and hearing loss, leading to deafness, develop within about 5 hours, usually with regression within 48 hours, but permanent damage can occur. Disturbed balance, often with vertigo, can develop, as well as nausea, usually with maintenance of consciousness, even without treatment. It has been postulated that in this state depolarization of the cochlear hair cells occurs, similar to the changes induced by pressure. Tinnitus is also a symptom of salicylism. 

In vitro models permit direct access to tissues and easy manipulation of experimental conditions. Most models are designed to monitor only hair cells and supporting cells, whereas lateral wall tissues that control the ionic balance in the inner ear or neurons are generally not accessible (see Table 2). 

As mentioned above, SlP2-null mice lose hearing and have balance defects (Herr et al., 2007 Kono et al., 2007 MacLennan et al., 2006). It may be possible to prevent the degeneration of hair cells with a selective SIP signaling modulator. These studies are ongoing and may offer novel treatment modalities for the prevention of age-related and ototoxic hearing loss. 

Fleadache may precede the onset of labyrinthine dysfunction, followed immediately by nausea, vomiting, and difficulty with balance, which develop acutely and persist for 1-2 weeks. The acute stage is followed by manifestations of chronic labyrinthitis, in which the patient has difficulty when attempting to walk or make sudden movements ataxia is prominent. The chronic phase persists for 2 months. Recovery may require 12-18 months most patients have some permanent residual damage. Although there is no specific treatment for the vestibular deficiency, early drug discontinuation may permit recovery before irreversible damage of the hair cells. 

Spector, A.A. and Jean, R.P. Modes and balance of energy in the piezoelectric cochlear outer hair cell wall,... 

The inner ear consists of the cochlea and the labyrinth, organs for hearing and balance respectively, with the eighth cranial nerve. This nerve has an auditory and a vestibular portion. The inner ear is filled with liquid. When sound waves strike the eardrum, between the external canal and the middle ear, this causes movements of the ear bones (hammer, anvil and stirmp). These movements are transferred into vibrations of the liquid in the inner ear, where the hair cells convert the movements to nerve impulses. The signals are sent to the brain through the auditory nerve. 

In addition to the classical symptoms of zinc deficiency mentioned above, the following unusual conditions have been reported liver and spleen enlargement, abnormal dark adaptation and abnormalities of taste. Several laboratory procedures for diagnosing zinc deficiency are available. Measurement of zinc levels in plasma is useful in certain cases. Levels of zinc in the red cells and hair may be used for assessment of body zinc status. More accurate and useful parameters are neutrophil zinc determination and quantitative assay of alkaline phosphatase activity in neutrophils. Determination of zinc in 24 h urine may help diagnose deficiency if sickle cell disease, chronic renal disease and liver cirrhosis are ruled out. A metabolic balance study may clearly distinguish zinc-deficient subjects. 

Proteins act as enzymes, hormones, and antibodies. They maintain fluid balance and acid and base balance. They also transport substances such as oxygen, vitamins, and minerals to target cells throughout the body. Structural proteins, such as collagen and keratin, are responsible for the formation of bones, teeth, hair, and the outer layer of skin, and they help maintain the structure of blood vessels and other tissnes. In contrast, motor proteins use energy and convert it into some form of mechanical work (e.g., dividing cells and contracting muscle). 

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