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