Transcript Introduction of hearing

Sajida Batool
M.sc(III)
Department of Biological science KIU
Importance of hearing
 Hearing may initially have
been important to
vertebrate as a mechanism
to alert them to dangerous
activities.
 It also important in search
for food and mates and in
communication.
Cont…..
Range;
 Humans are not able to hear
low pitched sounds, below
20 cycles per second .
 Young children can hear high
pitched sounds up to 20,000
cycles per second, but this
ability decrease with age.
Structure of human Ear
• The human ear has three
divisions…
1. The outer Ear
2. The middle Ear
(eardrum)
3. The inner Ear
Structure of human Ear
The outer Ear;
 The outer ear consist of the
 Auricle and external
auditory canal.
 Sound waves enter the
outer ear and create
pressure waves that
reached the tympanic
membrane.
Structure of human Ear
The middle Ear;
• The middle ear begin at the
tympanic membrane and
ends inside the skull.
• Where two small
membranous opening, the
oval and round windows , are
located.
• Three small ossicles are
between the tympanic
membrane & the oval
window.
Structure of human Ear
The middle Ear;
• They include the
Malleus; (hammer)
II. Incus; (anvil)
III. Stapes;(stirrup)
•
So name for their shapes.
•
The Malleus adheres to the
tympanic membrane & connect
to the incus.
•
The incus connects to the
stapes, which adheres to the
oval window.
I.
Structure of human Ear
The inner Ear;
The inner ear has three components.
The vestibule
semicircular canal
Cochlea
The first two, The vestibule &
semicircular canals, are concerned with
equilibrium.
• Continuous movement of the fluid in the
semicircular canal may cause motion
sickness or seasickness in human..
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Structure of human Ear
The inner Ear;
• Cochlea;
• In mammals the long coiled
sensory structure of the inner ear
that contain receptor for sound is
the cochlea.
• this structure provide more
surface area for receptor cells &
allow mammals greater sensitivity
to pitch & volume Then is present
in other animals.
Process of hearing
The process of hearing can be
summarized as follows;
1. Sound waves enter the outer ear
and create pressure waves that
reached the tympanic membrane.
2. Air molecules under pressure
vibrate the tympanic membrane.
3. The vibration move the Malleus to
the other side of the membrane.
4. The handle of the Malleus strike the
incus, vibrating it.
Process of hearing
5. The
vibrating incus moves the stapes back &
forth against the oval window.
6. The movement of the oval window set up
pressure changes that vibrate the fluid in the
inner ear. These vibrations are transmitted to
the basilar membrane, causing it to ripple.
7. Receptor hair cells of the organ of corti that are
in contact with the overlying tectorial
membrane are bent, causing a generator
potential , which leads to an action potential
that travel along the vestibulocochlear nerve
to the brain for interpretation .
Process of hearing
8. vibration in the cochlear fluid
dissipate as a result of movement
of the round window.
ANY QUESTION?
Thank you for your attention