hearing and equilibrium. auditory sensations and equilibrium hearing and equilibrium rely on...

Hearing and Equilibrium

Auditory sensations and Equilibrium

Hearing and equilibrium rely on mechanoreceptors

The ear is divided into three parts:Outer ear Middle ear Inner ear

Outer ear:

Ceruminous glands – Cerumen - ear wax

in external auditory meatus

Middle ear:

Tympanic antrum – opening into mastoid process

Auditory (Eustachian) Tube

Otitis media – inflammation of the MIDDLE ear

Auditory ossicles or ear bones

Tensor tympani muscle

Stapedius muscle

Tympanic reflex

INNER EAR :

Cochlea – hearing

Vestibule – static equilibrium

Semicircular canals – dynamic equilibrium

Organ of Corti

Vestibulocochlear nerve – cranial nerve VIII

Audible range: 20 -- 20,000 hertz

Ossicles amplify sound 22 X

Some nerve fibers cross over to opposite side of brain; some don’t. Why?

Equilibrium – Balance

Static equilibrium – maintenance of body posture relative to gravity while the body is still.

Dynamic equilibrium – maintenance of the body posture (mainly the head) in response to sudden movements. Tracking a moving object.

Static Equilibrium

Inside the vestibule are two chambers :

utricle and saccule.

Regions of hair cells and supporting cells called maculae.

Otoliths – “ear rocks”

Dynamic Equilibrium

Semicircular canals

In ampulla is the crista ampullaris – contains hair cells and supporting cells covered by a gelatinous mass called the cupula.

Neurological connections between eyes and semicircular canals – for tracking

Nystagmus