Vestibular apparatus

VESTIBULAR APPARATUS

1. DR NILESH KATE
MBBS,MD
PROFESSOR
ESIC MEDICAL COLLEGE, GULBARGA.
DEPT. OF PHYSIOLOGY
VESTIBULAR
APPARATUS

2. OBJECTIVES.
Functional anatomy
Vestibular receptors
Vestibular pathways
Mechanism of functioning
Functions
Maintenance of equilibrium
Applied aspects.

3. Functional anatomy.
Internal
ear/labyrinth–
petrous part of
temporal bone
Consists of
Bony labyrinth
Membranous labyrinth.
Tuesday, February 4, 2020

4. Bony labyrinth
3 parts
Vestibule
Semicircular canals
Cochlea
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5. Membranous labyrinth
In bony labyrinth
Filled with endolymph.
Surrounded by perilymph.
Consists of
Utricle & saccule –in bony
vestibule
Semicircular ducts –in
canals
Ducts of cochlea –in
cochlea
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6. Vestibular apparatus
Semicircular canals &
utricle & saccule
together called -
Vestibular apparatus
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7. Semicircular canals
Anterior
Posterior
Lateral
One end of each dilated
–ampulla which
contains receptor organ
–crista ampullaris.
They open into utricle
by 5 orifices.
Tuesday, February 4, 2020

8. Otolith organs
Utricle & saccules
together called –otolith
organs.
Utricle –larger, opens 3
semicircular canals
Connected to saccules &
endolymphatic sac
Saccules
Connected to utricle &
cochlea –ductus reunion.
Tuesday, February 4, 2020

9. Vestibular receptors
Hair cells
Location –of
semicircular canals in
mass of tissue within
ampulla-crista
ampullaris.
Of otolith organs in
macula.
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10. Tuesday, February 4, 2020

11. Hair cells
Type I
Type II
Cilia of hair cells –
stereocilia.
Large nonmotile –
kinocilium.
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12. Activity of hair cells
Rmp –60 mv
Steriocilia bend
towards –depolarize
Away –hyperpolarize.
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13. Receptors in semicircular
canals
Crista ampullaris.
Neuroepithelium
Secretory epithelial
cells
Cupula.
Unaffected by linear
acceleration
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14. Tuesday, February 4, 2020

15. Receptors in otolith organs
macula
Structure
Neuroepithelium
Supporting cells
Otolith membrane.
Contains crystals of Ca
carbonate –otoliths or
otogonia
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16. Stimulation of receptors in
otolith organs.
Macula of utricle
Linear acceleration.
Macula of saccule
Vertical acceleration.
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17. Vestibular pathways
First order neurons
Vestibular nuclei
Afferents
Efferents
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18. EFFERENTS
Vestibulospinal tract
Vestibulo-ocular
Vestibulo-cerebellar
Vestibulo-reticular
Vestibulo-rubral
Vestibulo-thalamo-
cortical.
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19. Tuesday, February 4, 2020

20. Mechanism of functioning
Mechanism of
stimulation –
At the beginning of
movements
At the end of
movements.
Mechanism of
adaptation. –after 15-
20 sec of continuous
movement.
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21. Functions
Utricle –
Stimulated during
horizontal acceleration
Saccules –
Stimulated during
vertical acceleration
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22. Vestibular reflexes
Vestibulo-ocular
Otolith reflexes –
prevents leg injuries
during jump.
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23. Vestibulo-ocular
Nystagmus
Slow component
Fast component.
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24. Functions of vestibular
apparatus
Role in maintenance of
equilibrium
Role in maintenance of
posture.
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25. Maintenance of equilibrium
Otolith organs –linear
acceleration
Semicircular canals –
angular acceleration.
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26. Role in maintenance of
posture.
Vestibular placing
reaction
Righting reflexes
Vestibulo ocular reflex
Vestibulo-otolith
reflex.
Tuesday, February 4, 2020

27. Applied aspects
Vestibular dysfunction
Experimental
stimulation of
semicircular canals
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28. Vestibular dysfunction
Motion sickness
Benign paroxysmal
positional vertigo
Miniere’s disease
Labyrinthetcomy
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29. Experimental stimulation of
semicircular canals
Stimulation of
rotational movements
by Barany’s chair
Calorie stimulation
Tuesday, February 4, 2020

30. THANK YOU