The vestibular system and hearing physiology document discusses: 1) Hearing involves sound waves vibrating the outer, middle, and inner ear to stimulate hair cells and nerves that transmit signals to the brain. 2) The ear has three parts - outer, middle, and inner ear - that work together to detect sound and maintain balance. 3) The vestibular system in the inner ear maintains balance through the utricle, saccule, and three semicircular canals that detect head movement and position.

1. VESTIBULAR
SYSTEM AND
HEARING
PHYSIOLOGY
A D A M B I L S K I

2. SOUND
Hearing belongs to vibrational senses, as sound is a vibration
that typically propagates as an audible wave of pressure,
through a transmission medium such as a gas, liquid or solid.
Humans can only hear sound waves as distinct pitches when
the frequency lies between about 20 Hz and 20 kHz.

3. EAR
• In mammals ear = hearing + balance
• 3 parts – outer ear (pinna/auricle, ear canal and membrane), middle ear
(tympanic cav., 3 ossicles), inner ear (semicircular canals, utricle, saccule,
cochlea)
• Location of ears on both sides of head – binaural hearing

4. HEARING
First - sound comes in through,
caught by pinna (funnel-
shaped collector of sound),
until it reaches tympanic
membrane in the middle ear,
which is still part of conductive
apparatus.
Outer ear increases sound
intensity by 15-20 dB

5. HEARING
• The air molecule under pressure causes vibration of
tympanic membrane. Low frequency sound wave causes
slow vibration while high frequency wave causes rapid
vibration.

6. • The vibration of tympanic membrane moves the
malleus in middle ear, the vibrating malleus produces
vibration to incus and vibrating incus moves stapes in
and out of oval window causing vibration of perilymph
in scala vestibuli.

7. • Vibration of perilymph are transmitted across the
vestibular membrane to endolymph in scala media
(cochlear duct) and also up the scala vestibuli and
down the scala tympani.

8. • The vibration of scala tympani are dissipated out of
cochlea through round window into Eustachian
tube.

9. • During transmission of vibration from perilymph to
endolymph in scala media, the basilar membrane
ripples. This ripple is concerned with frequency and
intensity of sound.

10. • The vibration of tympanic membrane moves the
malleus in middle ear, the vibrating malleus produce
vibration to incus and vibrating incus moves stapes in
and out of oval window causing vibration of
perilymph in scala vestibuli.

11. •The vibration causes bending of receptor of
hair cells of organ of corti to generate
potential, which excites cochlear nerves,

12. When the hair or microvilli of hair cells are
displaced toward the basal body, hair cells get
excited and when the hair are displaced away
from basal body hair cells are inhibited.

13. The nerve impulse from cochlear nerve are
conveyed to auditory area of CNS via common
vestibule-cochlear nerve. The auditory area is
located in temporal lobe where sound is
perceived.

14. VESTIBULAR SYSTEM
Vestibular system is for
maintaining position and
movement of the head and
balance of the whole organism.
The components of the
vestibular system are:
• Utricle
• Saccule
• Three semicircular canals

15. UTRICLE AND SACCULE
They are two so-called Otolith organs, saccule detects
backward-frontward movement utricle detects changes
relative to gravity.

16. OTHOLITS
Calcium carbonate crystals in contact with hair cells,
reacting to change of position of head with movement,
changing position of hair cells.,

17. SEMICIRCULAR CANALS
• Detect angular acceleration of 3
dimensions of movement
• There are three semicircular canals
arises from utriculus; anterior, posterior
and lateral canals
• The anterior and posterior canals opens
at one end to form common duct called
crus commune. One end of each
semicircular canal is swollen to form
ampulla (hair cells = cristae here)

18. 1. Angular acceleration causes endolymph fluid to
move
2. This pushes the cupula
3. Cupula stimulates the hair cells
4. Hair cells synapse with vestibular nerve fibers

19. The parietal vestibular field is in the
frontal lobe.
Another center is localized in area 7 in
the posterior parietal cortex. Many
cortical vestibular neurons respond to
proprioceptive stimulation - the
rotation of joints - as well.

20. THANK YOU FOR
ATTENTION 