Vestibular apparatus and balancing role human

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

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

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

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

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

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

15. Vestibular pathways First order neurons Vestibular nuclei Afferents Referents

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

17. 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

18. Functions Utricle- - Stimulated during horizontal acceleration Saccule - - Stimulated during vertical acceleration

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

20. Vestibulo-ocular Nystagmus Slow component Fast component

21. Functions of vestibular apparatus Role in maintenance of equilibrium Role in maintenance of posture

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

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

24. Applied aspects Vestibular dysfunction Experimental stimulation of semicircular canals

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

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

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

28. Thank you