Vestibular Physiology

Question 1

Divisions of vestibular system ?

Answer 1

Peripheral - consists of membranous labyrinth (utricle,saccule,semicircular canals) and vestibular nerve

Central - consists of nuclei and fibre tracts that integrates vestibular impulses with other systems of the body(vestibulo-ocular pathway and vestibulo-spinal pathway)

Question 2

What senses rotational acceleration?

Answer 2

Cristae of the semicircular canals senses rotational / angular acceleration

Question 3

What senses linear acceleration?

Answer 3

Maculae of vestibule (utricle and saccule) senses the linear acceleration

Question 4

How many semicircular canals are there and what are they?

Answer 4

3 semicircular canals ; all are at right angles to each other placed in different planes

They are:

Lateral / horizontal scc - is at 30 degrees above the horizontal

Superior / anterior scc - vertical - is placed at 45 degree anterior to the Sagittal plane

Posterior scc - vertical - is placed at 45 degree posterior to the sagittal plane

Question 5

How is the vestibular system activated upon movement of head ?

Answer 5

On turning the head , vestibular system of the same side gets activated

When the head is straight and looking straight , both vestibular system are equally activated

Question 6

What is the most common cause of vertigo?

Answer 6

Positional vertigo

Question 7

What is the cause for positional vertigo ?

Answer 7

Otoliths from the maculae gets dislodged and enters into the semicircular canal on moving the head , irritates the semicircular canals causing positional vertigo

Vertigo occurs when direction of the involved canal gets engaged

Question 8

What is the most common scc affected in positional vertigo ?

Answer 8

Posterior scc

Question 9

What is the manoeuvre for positional vertigo ?

Answer 9

Epley’s manoeuvre

Question 10

What is the sensory end organ for angular / rotational acceleration in cupula?

Answer 10

Cristae

Question 11

How is Cristae stimulated to release neurotransmitter?

Answer 11

When the all the cilia move towards the kinocilium(longest cilia) causes release of neurotransmitter

Question 12

Ewald’s second law

Answer 12

Ampullopetal endolymphatic flow produces a stronger response than ampullofugal flow in horizontal scc

Question 13

Ewald’s third law

Answer 13

Amupullofugal flow produces a stronger response than ampullopetal flow in vertical canals