The Ear’s Role in Balance and Equilibrium

The Ear Houses two senses Hearing Equilibrium (balance) Receptors are mechanoreceptors Different organs house receptors for each sense

Anatomy of the Ear The ear is divided into three areas External ear Middle ear Inner ear

The External Ear Involved in hearing only Structures of the external ear Pinna (auricle) External auditory canal

The Middle Ear Air-filled cavity within the temporal bone Only involved in the sense of hearing Two tubes are associated with the inner ear The opening from the auditory canal is covered by the tympanic membrane The auditory tube connecting the middle ear with the throat Allows for equalizing pressure during yawning or swallowing This tube is otherwise collapsed Three bones span the cavity Malleus (hammer) Incus (anvil) Stapes (stirrup) Vibrations from eardrum move the malleus These bones transfer sound to the inner ear

The Inner Ear or Bony Labyrinth Includes sense organs for hearing and balance Filled with perilymph A maze of bony chambers within the temporal bone

Organs of the Inner Ear Semicircular canals – organ for dynamic equilibrium Cochlea – organ for hearing Vestibule – organ for static equilibrium

Organs of Equilibrium Receptor cells are in two structures Vestibule (static) Semicircular canals (dynamic) Equilibrium has two functional parts Static equilibrium Dynamic equilibrium

Static Equilibrium receptors are in the vestibule Maculae – receptors on the membranes of the vestibule Report on the position of the head Send information via the vestibular nerve

Dynamic Equilibrium receptors are in the semicircular canals Crista ampullaris – receptors in the semicircular canals Tuft of hair cells Cupula (gelatinous cap) covers the hair cells Action of angular head movements The cupula stimulates the hair cells An impulse is sent via the vestibular nerve to the cerebellum

Review of the balance and equilibrium organs in the inner ear STATIC EQUILIBRIUM – position of the head in space The organ is the vestibule The receptor inside the vestibule is the maculae DYNAMIC EQUILIBRIUM – action of angular head movements The organ is the semicircular canals The receptor inside the semicircular canals is the crista ampullaris

Symptoms of Meniere’s Disease The symptoms of Ménière’s disease are episodic rotational vertigo (attacks of a spinning sensation) Hearing loss Tinnitus (a roaring, buzzing, or ringing sound in the ear) A sensation of fullness in the affected ear.

Meniere’s Disease A disorder of the inner ear. Although the cause is unknown, it probably results from an abnormality in the fluids of the inner ear. Ménière’s disease is one of the most common causes of dizziness originating in the inner ear. In most cases only one ear is involved, but both ears may be affected in about 15 percent of patients. Ménière’s disease typically starts between the ages of 20 and 50 years. Men and women are affected in equal numbers.