About vestibular apparatus in human

1. Vestibular
apparatus
By -Ujjwal Pratap
Shahi
Roll No - 178

2. Objectives
• Functional anatomy
• Vestibular receptors
• Vestibular pathways
• Mechanism of functioning
• Functions
• Maintenance of equilibrium
• Applied aspect

3. Functional anatomy
• Internal ear/ labyrinth- petrous
part of temporal bone
• Consists of - bony labyrinth and
membranous labyrinth

4. Bony labyrinth
• 3 parts
• Vestibule
• Semicircular canals
• Cochlea

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

6. Vestibular apparatus
• Semicircular canals & utrile and
saccule together called -
vestibular apparatus

7. Semicircular canals
• Anterior
• Posterior
• Lateral
• One end of each dilated - ampulla
which contains receptor organ -
Christa ampullaris
• They open into utricle by 5 orifices.

8. Otolith organ
• Utricle & saccule together called - otolith
organ.
• Utricle - larger, opens 3 semicircular canals
• Connected to saccule &
endolymphatic sac
• Saccules
• Connected to utricle & cochlea -
ducts reunion

9. Vestibular receptor
• Hair cells
• Location - of semicircular canals
in mass of tissue within ampulla -
crista ampullaris
• Of otolith organs in macula

11. Hair cells
• Type 1
• Type 2
• Cilia of hair cells - stereocilia
• Large non-motile - kinocillium

12. Activity of hair cells
• RMP - 60mV
• Stereocilia bend towards -
depolarise
• Away - hyperpolarize

13. Receptors in
semicircular canals
• Crista ampullaris
• Neuroepithelium
• Secretary epithelial cells
• Capula - unaffected by linear
acceleration

15. Receptors in otolith organs
- macula
• Structure
• Neuroepithelium
• Supporting cells
• Otolith membrane
• Contains crystals of Ca
Carbonate - otoliths or
otogonia

16. Stimulation of receptors in otolith
organs
• Macula of utricle
• Linear acceleration
• Macula of saccule
• Vertical acceleration

17. Vestibular pathways
• First order neurons
• Vestibular nuclei
• Afferents
• Referents

18. Efferents
• Vestibulospinal tract
• Vestibulo-ocular tract
• Vestibulo-cerebellar tract
• Vestibulo-reticular tract
• Vestibule-rubral tract
• Vestibule-thalamo-cortical tract

20. Mechanism of functioning
Mechanism of stimulation-
-At the beginning of the
movements
- At the end of the movements
Mechanism of adaptation- after
15-20 sec of continuous
movement

21. Functions
• Utricle-
- Stimulated during horizontal
acceleration
Saccule -
- Stimulated during vertical
acceleration

22. Vestibular reflexes
• Vestibulo-ocular
• Otolith reflexes - prevents leg injuries during jump

23. Vestibulo-ocular
• Nystagmus
• Slow component
• Fast component

24. Functions of vestibular apparatus
• Role in maintenance of equilibrium
• Role in maintenance of posture

25. Maintenance of equilibrium
• Otolith organs - linear acceleration
• Semicircular canals - angular acceleration

26. Role in maintaining posture
• Vestibular placing reaction
• Righting reflexes
• Vestibulo-ocular reflex
• Vestibule-otolith reflex

27. Applied aspects
• Vestibular dysfunction
• Experimental stimulation of semicircular canals

28. Vestibular dysfunction
• Motion sickness
• Benign paraoxysmal positional vertigo
• Miniere’s disease
• Labyrinthetcomy

29. Experimental stimulation of semicircular
canals
• Stimulation of rotational movements by barany’s chair
• Calorie stimulation

30. References
• Guyton and Hall textbook of medical physiology
• Comprehensive textbook of medical physiology by G K pal

31. Thank you