vestibular apparatus

2. The Vestibular Apparatus
(Function)
PBL-2
23rd -March-2018

3. Objectives
• To describe the functions of vestibular apparatus

4. • Vestibular system consist of
Vestibular apparatus and vestibular nucleic

8. Vestibular Apparatus
• Sensory organ for detecting
sensations of equilibrium.
• Consists of 2 ottolith organs and
3 semicircular canals

9. • Sensory hair cell found in vestibular apparatus
• Mechanically (Inertia or gravitational force) disturbed hair cell get
stimulated

11. Otolith Organs
(Vertical and Linear Acceleration)

12. Otolith organ
• Are two sac like structures named Saccule and
Utricle
• The sensory hair cells of these organs lies in the
macula
# Saccule
- Vertically oriented maculae
Detect – upward and downward movement
# Utricle
– horizontal orientation of maculae
Detect - side to side movement

14. Macular Orientation

15. Also,
• The combine sense of utricle and macule gauge the linear forces
acting on the head at any instant in 3D.

16. Semicircular Canal
(Angular Acceleration )

17. Semicircular Canals
• Anterior
• Posterior
• Lateral
Arranged in 90 Degree to each
other
Ampulla as a sensory organ

18. • Semicircular canal works in pairs
3 pairs
1. Horizontal pairs
2. Lt. Anterior and Rt. Posterior
3. Rt Anterior and Lt. posterior

20. Vestibular nuclei
• Sensory impulse from Vestibular apparatus are conveyed and processed at
vestibular nuclei
• Vestibular nuclei – a multisensory structure
( visual , somatosensory, vestibular nuclei of opposite side)

22. Two major classes of Reflexes
A. for maintaining equilibrium and gaze during movement
- Vestibulo-ocular reflex (VOR)
B. For maintaining Posture
- Vestibulo-Spinal relex (VSR)
- Vestibulo-Cervical reflex (VCR)

23. 1. VOR

24. 2. VCR
• Medial vestibular nuclei – medial longitudinal fasciculis
• Maintain head position reflexly
3. VSR –
• lateral vestibular nucleus - vestibule-spinal tract
• Balance and upright positon

27. Spatial Orientation and self motion
Vestibulo-visual interaction
• Visual flow generates strong sense of self-motion while the subject is not
moving (Vection)
• In this case , vestibular system suppress the sense of self generated motion
(Astronauts , pt with vestibular damage)

28. Reference
• Guyton and Hall, 13th edition
• Ganong’s Review of Medical Physiology 24th edition
• Neuroscience 5e,purves et al. 2012

29. Thank you