2. Vestibular apparatus is a complex sense
organ of inner ear
Primary organ for equlibrium
Is required for-
▪the movement of the eye that
accompany the movement of the head
▪detection of various movements and
positions of the head
3. Internal ear consists of-
Bony labyrinth-
bony structure of inner ear
Membranous labyrinth
Cochlea and vestibular apparatus are
situated here
5. Lie in temporal bone on each side of the
head
It consists of-
▪ three semicircular canal
▪utricle and saccule (the otolith organ)
6.
7.
8. Are three in numbers-
horizontal (lateral)
superior (anterior)
inferior (posterior)
●All three canals are at right angles to each
other
9. Ampulla- each canal begins as a dilatation
called ampulla
All three canals open into the utricle
Utricle opens into the saccule through a duct
called Ductus endolymphaticus
Saccule communicates with cochlea
10. Crista is the receptor present in semicircular
canal
In the ampulla there is a ridge
On ridge are hair cells which give rise to
hairs
Cupula-
hairs and gelatinous substance
Crista-
cupula and hair cells
11.
12. Macula is the receptor present in utricle and
saccule
In utricle and saccule ridge like structure
hair cells and hair is present
Otolith membrane-
hairs and gelatinous material
Macula-
Otolith membrane and hair cells
13. Kinocilium-
▪present at one end of hair cell
▪large non motile hair
Stereocilia-
▪present in the remaning hair cells
▪are small with progressive increase in
height
14. Hair cells are of two types-
▪Type I –flask shaped
▪Type II-most common type
15.
16. Nerve fibers from cristae and maculae
↓
Form vestibular division of 8th nerve
↓
Vestibular ganglion(Scarpa`s ganglion)
↓
Central axon proceeds towards the brain stem
↓
Enters brain stem and end in vestibular nucleus
17. Efferent fibers from vestibular nucleus
terminates in-
1.In the 3rd,4th,6th cranial nerve nuclei via
median longitudinal fasciculus
2.Anterior horn of spinal cord via lateral
vestibulospinal tract
18. 3. In the cerebellum
4.Nuclei of reticular formation of the brain
stem
5.Temporal lobe of opposite side via the
opposite thalamus
6.Some fibers go back to the hair cells
19. Semicircular canal detects angular
acceleration during rotation of head along
three perpendicular axes
Stimulus to each ampulla is rotation of the
head
Posterior canal of one side
and
Anterior canal of other side
form a pair
20. Two horizontal canal of both sides make a
pair
Semicircular canal signals changes in
acceleration but are insensitive to constant
rotatory movement
21.
22. Saccule and utricle gives information about
linear acceleration
and
change in head position relative to the gravity
Saccule → Vertical acceleration
Utricle → Horizontal acceleration
23. Maculae of the saccule and utricle are stretch
receptors
Stimulus for maculae is pull of the gravity on
the otolith membrane
The hairs are deformed resulting in
stimulation of the nerve fibres
24. Saccule are affected by lateral tilt of the
head
Utricle are affected by nodding the head up
and down
Movement of stereocilia towards the
kinocilium increases action potential
frequency
25.
26. It is a sense organ of balance
-Balance is regained by righting reflex
Vestibulo-ocular reflex
- When the head is moving towards a
given direction, the eyes move to the
opposite side
28. Enable the erect position of the head and the
normal posture of the body is maintained
Semicircular canal gives information about
movement of the head
Otolith organ gives information about position of
the head
29. 1. MOTION SICKNESS-
▪is a syndrome consisting of nausea, vomiting,
headache, vertigo
▪ occurs during travelling
▪due to overstimulation of vestibular
apparatus
30. 2. SEA SICKNESS
▪ type of motion sickness occuring
during travelling by sea
▪results from irregular and repetitive
motion of the ship
31. 3. MENIERE`S DISEASE
▪Disorder involving vestibular apparatus
▪ Episodes of dizziness (vertigo),tinnitus
and hearing loss
▪ Due to distension of endolymphatic
system
32. Drug treatment
▪ Bed rest
▪ Vestibular sedative
▪ Vasodilator like histamine
Surgical treatment
▪Decompression of endolymphatic sac
▪Sacculotomy
▪ Section of vestibular nerve
33. 4. DRUG INDUCED DAMAGE
-By streptomycin when used in heavy dose for
treatment of tuberculosis
34. NYSTAGMUS
▪ Involuntary jerky oscillation of eyes
▪ Railwayman`s nystagmus- seen in normal
person
▪Cause of pathological nystagmus
-Disease of cerebellum
- Vestibular dysfunction
- Weakness of extra-ocular muscles of
eyes ( Myasthenia gravis)
35. LABRYRINTHECTOMY
-Removal of labyrinth
a) Unilateral labrinthectomy
- There is derangement of postural activity
-Nystagmus
37. Romberg`s sign
-Test for loss of position sense
Barany`s Caloric test
-Diagnostic purpose
-Semicircular canal are stimulated
-Water is at 30˚ C or 44˚ C
- Causes nystagmus ,vertigo and nausea
38. Fistula test
- To induce nystagmus by producing pressure
changes in the external canal which are then
transmitted to the labyrinth
-Normally the test is negative