Download Ear

Hearing
What’s that
you say?
Anatomy is
your favorite
class? Not
surprising.
The Ear
• Complex organ consisting of outer, inner, and middle
regions
– Outer Ear = transmits sound waves through air
– Middle Ear = transmits sound waves through bone
– Inner ear = transmits sound waves through liquid
• Cochlea converts sound waves into electrical impulses to brain
• Vestibular apparatus is involved in equilibrium not hearing
Outer and Middle Ear
• Sound waves collected
and directed down the
auditory canal where they
hit the tympanic
membrane (eardrum)
• Vibrations of the eardrum
are amplified and
transmitted to the inner
ear via three tiny bones
• Ossicles = tiny bones of
the middle ear. Smallest
bones of the body.
– malleus, incus, stapes
Pharyngotympanic
Tube
• Tube which links the
middle ear cavity with
the throat.
• Tube usually closed but
opens when swallowing
or yawning.
• Helps equalize pressure
between the middle ear
and outside.
Often called Eustacian Tube
Inner Ear
• Oval window is
the beginning of
the cochlea
• Fluid is pushed
through cochlea
and bulges
outward the
round window at
the end
Inner Ear Cochlea
• Movements of the stapes bone
hitting the ear drum are
transmitted to the oval window
(start of cochlea)
• Vibrations move through the
fluid in the cochlea
• Organ of Corti in the cochlea is
the sensory organ for hearing
• Contain hairs that are triggered
as sound vibrations pass
through. When activated,
sensors causes brain to receive
electrical signal.
Signal Generation
• Change in individual hair position
triggers electrical signal to be sent
to brain. Each hair a specific sound
(“note”).
• Signals transmitted to hearing
portion of temporal lobe of brain
• Brain interprets signals as sound
perception
• Use vestibulocochlear nerve to
reach the auditory cortex of the
brain (temporal lobe)
Equilibrium
Semicircular canals in the
vestibular portion of the
inner ear detect rotational
acceleration or deceleration
Small stones inside move around
like sand in an hour glass pushing
on hairs lining its membrane.
Equilibrium
The utricle and saccule in the
vestibular part of the inner ear
detect linear movement in any
direction by using otoliths
(calcium carbonate) = “rocks”
Utricle: horizontal displacement
Saccule: vertical displacement
Equilibrium