Inner Ear Balance Mechanisms

Balance Mechanisms Vestibule Semicircular Canals

Static Equilibrium

Static Equilibrium associated with vestibule receptors in chambers - saccule and utricle and contain maculae

Static Equilibrium Reports on body position in respect to gravity Responds to linear acceleration

each maculae is a flat patch of epithelium with scattered supporting cells and 20-50 receptor “hair” cells

hair cells are embedded in a jelly-like membrane that also contains tiny Ca crystals called otoliths (ear stones)

displacement activates receptors because hair cells move

Dynamic Equilibrium

Dynamic Equilibrium monitored by the ampullae at base of the semicircular canals evaluates the change in rate of movement

inside each is a crista ampullaris with hair cells in jelly covering - cupula Semicircular canal ampulla hair cell

each canal orients in a different place so acceleration at all angles can be monitored

if constant rotation occurs, hairs will quit bending and bend the other way when we stop bony labyrinth moves with body - fluid and gels move at various rates depending on different forces

Ear Disorders

Motion Sickness difficult to explain probably due to sensory input mismatch caused by continuous stimulation of the semicircular canals consists of nausea and weakness

Deafness or hearing loss can be: Conduction Outer ear or middle ear Sensorineural Inner ear

1. Conduction something interferes with vibrations or transmission of sound waves

Examples of causes: ear wax build up ruptured eardrum

Examples of causes: otosclerosis - connective tissue grows over stapes and oval window

helped by hearing aid and surgery

2. Sensorineural Involves damage to the organ of Corti hair cells or nerve pathways

Examples of Causes: Loud noise that pulls hair cells away from nerve endings

Examples of Causes: Tumors

Cochlear implants convert sound to electrical stimuli delivered to the cochlear nerve