Physiology of Equilibrium

Question 1

Semicircular canals parts

Answer 1

Anterior, posterior, horizontal

DETECT ROTATION due to rotation endolymph

Question 2

Functional region of semicircular canal

Answer 2

Dilation called the ampulla, with sensory epithelium known as the Ampullary crest:
- Hair cells covered by a cupula gel: same density as surrounding endolymph

Question 3

What happens when a person’s head rotate?

Answer 3

Endolymph moves through the semicircular canals, causing the cupula to move and placing MECHANICAL stress on the hair cells.
Initially in the opposite direction to head movement, only transient: Because head movement is FASTER than the fluid movement in the semicircular canal.
Finally, the endolymph will move in the same direction as the head movement.
When the rotation stop, endolymph will continue to move, but this will cause mechanical deformation of the hair cells in the opposite direction.
HEAD ROTATION TO THE LEFT:
Left horizontal semicircular canal will bend toward the kiniocilium
Right horizontal semicircular canal will bend away from the kiniocilium

Question 4

Parts of the Saccule and Utricle

Answer 4

Otolithic membrane covering the sensory epithelium.

Otholiths = calcium carbonate

Question 5

Function of the Saccule and Utricle

Answer 5

Detect change of the position and linear acceleration of the head
- detect change in position and linear acceleration in the head due to the density of otoliths resulting in a different inertia in the otolithic membrane gel

Question 6

Hair cells of saccule and utricle are located in a sensory epithelium region called:

Answer 6

The macula

Question 7

In which direction is the utricle oriented?

Answer 7

Horizontally

Question 8

In which direction is the saccule oriented?

Answer 8

Vertically (SV)

Question 9

The hair cells are oriented in relation to a groove…

Answer 9

Striola, runs in the middle of the macula

The action potential will increase on one side of the striola and decrease on the other side of the striola

Question 10

Saccula macula - orientation of the kiniocilia in relation to the striola

Answer 10

Away from the striola (hodet er orientert away fra sekken)

Question 11

Utricle macula - orientation of the kiniocilia in relation to the striola

Answer 11

Towards the striola

Question 12

Difference between the hair cells in the cochlea and in vestibular apparatus
Mechanism of depolarization

Answer 12

• Kiniocilium, which helps define the orientation of the hair cells.
• Mechanism of Depolarization: mechanical pressure pushes the stereocilia towards the kiniocilium
• Opening of TRP cation channels - potassium influx

Question 13

The difference between the endolymph in the cochlea and the vestibular apparatus?

Answer 13

Endolymph cochlea: +80 mV

Endolymph Vestibular apparatus: 0 mV

Question 14

Electrochemical gradient

Answer 14

0mV - (-40mV) = + 40mV

Question 15

Types of hair cells in the vestibular apparatus

Answer 15

Type I: Afferent dendrite is round, surrounding the hair cell
Type II: small afferent dendrite, receive stronger efferent input to modulate their effects

Question 16

Vestibular pathway

Answer 16

Primary afferent - Brainstem via vestibular nerve CN VIII - terminate in the vestibular nuclei - connect with cerebellum, reticular formation, oculomotor nuclei, spinal cord

Question 17

Vestibulospinal reflex

Answer 17

Help reorient the body with extensor muscle contraction if falling

Question 18

Vestibulo - ocular reflex

Answer 18

Help focus on moving objects or stationary objects while moving by a process called nystagmus

Question 19

Dysfunction of the vestibular system leads to

Answer 19

VERTIGO