The Vestibular System

Question 1

Describe the role of hair cells in vestibular system

Answer 1

Type 1 - more in number, direct afferent and indirect efferent
Type 2 - direct afferent and efferent
They synapse from cell body in scarpas ganglion to vestibular nuclei in brainstem.

Hair cells are stimulated by deflection of forces of inertial resistance to acceleration for otoliths and endolymphatic fluid rotation in canals.

Hair cell potential: towards kinocillium = depolarisation (increase firing from ganglion) and away = hyperpolaristion (decreased frequency and firing)

Question 2

Describe the otolith organs and their role

Answer 2

The otolith organs: maculae (utricle and saccule), hair cells, gelatinous matrix (on top of hair cells) and otoliths (carbonate crystals on top of hairs), Striola (opposing hair bundle polarities in the middle). Movement in any direction stimulate a distinct subset of cells.

The vector sum of the utricular and saccular stimulations pattern gives signal of linear acceleration in 3D motion.

Question 3

Describe the role of semi circular canals

Answer 3

Hair cells project from the ampulla (hair cells in crista) and are unidirectional so that the acceleration of side of head stimulated the canals on that side and the decelarates to stop the canal on the opposite side to be stimulated.

Question 4

Describe the blood supply

Answer 4

Look at slide

Question 5

Describe the vestibular pathway and function

Answer 5

Look at diagram

To detect and inform about head movements, to keep images fixed in retina during head movement s

Question 6

Describe unilateral lesions and balance disorders

Answer 6

Unilateral lesion: diagnosing via anamnesis, cranial nerves, balance and gait, cerebellum, imaging. Symptoms: vertigo, dizziness, unsteadiness self motion

Balance disorders: peripheral = labyrinth + VIII nerve eg BPPV or central - CNS eg stroke