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

4.  Perilymph-
Fluid between bony and membranous
labyrinth
● Endolymph-
Fluid within membranous labyrinths

5.  Lie in temporal bone on each side of the
head
 It consists of-
▪ three semicircular canal
▪utricle and saccule (the otolith organ)

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

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

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

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

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

27. Otolith reflex-
prevent injuries when a person walks
downstairs or jumps from a platfrom

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

36. b) Bilateral labyrinthectomy
- Individual behaves normally ,if
allowed to use the vision
- Muscle tone is decreased

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