.

1. Anatomy & Physiology of Vestibular
System

3. The inner ear composite of :
 Bony Labyrinth
1. Cochlea (Spiral shaped, making 2/3 turns around its axis).
2. Vestibular.
3. Semicircular Canals: Anterior (Supirior) , Lateral (Horizontal) &
Posterior.
 Memranous Labyrinth (which is found inside the bony labyrinth)
1. Organ of corti (in the cochlea) the sensory organ of hearing.
2. Utricle and saccule (in the vestibule) They are sensitive to linear acceleration.
3. Semicircular ducts (in the semicircular canals) They are responsible for angular
acceleration.

4. The Vestibular System
• It lies the otic capsule in the petrous portion of the temporal bone.
• It consists of 5 distinct end organs:
 3 semicircular canals that are sensitive to angular acceleration
(head rotations).
 otolith organs “utricle & saccule” that are sensitive to linear
(or staraight-line) acceleration.

6. Fluids in
Vestibular
System
Perilymph
In bony labyrinth
(low potassium, high
sodium)
Endolymph
In membranous
labyrinth
(high potassium, low
sodium)

7. otolith organs
(Utricle &
Saccule)
Sensory organ
maculae
Hair cells and
Supporting cells
Responsible for linear acceleration and
pull of gravity.
consisting :
60-80 small cilia are called stereocillia
one large cilium called kinocilium

8. Physiology of macula
• When stereocilia bend to the direction of kinocilium, it result in opening of K+
channels at the tip of the stereocilia, allowing K+ ions to enter and depolarize the
hair cell.
• In response to depolarization voltage-gate ca+2 channels are active allowing for
Ca+2 influx and the sebsequent liberation transmitters to produce an action
potential.

10. Macula
• In the utricle, macula lies in the horizontal plane of the inferior surface
determine forward-backward movement, left-right, combination.
• In the saccule, macula lies in the vertical plane and sense motion in the
sagittal plane (eg, up-down movement).

12. The Semicircular Canals:
• Lateral and Horizantal, Anterior or superior and Posterior.
• The semicircular canals are connected to the utricle at their bases.
• At the end of each canal is an enlarge chamber, the ampulia.
• The ampulla contains a sensory receptor called crista ampullaris.

13. Disorders of
Vestibular
System
Peripheral, which involve vestibular
end organs and their 1st order
neurons (i.e. the vestibular nerve).
Meniere's disease
benign paroxysmal positional Vertigo (bppV)
Vestibular neuronitis
Vestibulotoxic drugs, Head trauma
perilymph Fistula, Syphilis
Central, which involve central nervous
system after the entrance of vestibular
nerve in the brainstem and involve
vestibulo-ocular, vestibulospinal and
other central nervous system
pathways.
Vertebrobasilar insufficiency
Posteroinferior cerebellar artery syndrome
(wallenberg syndrome)
Basilar migraine, Cerebellar disease
Epilepsy, Cervical Vertigo
Tumours of brainstem and Floor of IVth Ventricle
OTHER CAUSES OF VERTIGO
1. Ocular Vertigo. Normally, balance is maintained by integrated information received from the eyes,
labyrinths and somatosensory system. A mismatch of information from any of these organs causes vertigo and
in this case from the eyes.
2. Psychogenic Vertigo. This diagnosis is suspected in patients suffering from emotional tension and anxiety.
Often other symptoms of neurosis, e.g. palpitation, breathlessness, fatigue, insomnia, profuse sweating and
tremors are also present.