The Vestibular System

Question 1

what is the point of the vestibular system?

Answer 1

it tells us which way is up and where we are going.

Question 2

what does the vestibular system contribute to?

Answer 2

keeping our eyes still as we move,
maintaining upright posture,
and our ability to perceive our own movement within space.

Question 3

what is the gross anatomy of the vestibular system?

Answer 3

the semi-circular canals,
an enlargement at the end of the canals called Ampulla,
and the otolith organs.

Question 4

what are the structures in the vestibular system that relate to head rotation?

Answer 4

the semi-circular canals.

Question 5

what are the structures in the vestibular system that relate to head tilt and linear motion?

Answer 5

the otolith organs.

Question 6

what are the 3 semi-circular canals (scc) ?

Answer 6

the anterior vertical scc,
the posterior vertical scc,
the horizontal vertical scc.

Question 7

what are the 2 otolith organs?

Answer 7

the Utricle,

the Saccule.

Question 8

where are the hair cells located?

Answer 8

in the Ampulla and in the Saccule/Utricle.

Question 9

what happens when the hair cells are at rest?

Answer 9

the bundles are upright and not being stimulated in a direction.

Question 10

what happens when the hair cells are being stimulated? (towards taller stereocilia)

Answer 10

fluid moves hair bundles towards the taller stereocilia,
results in depolarisation,
and increased in frequency of nerve impulses.

Question 11

what happens when the hair cells are being stimulated? (towards shorter stereocilia)

Answer 11

fluid moves hair bundles towards the shorter stereocilia,
results in hyperpolarisation,
and decreased impulse frequency.

Question 12

how are hair cells in the vestibular system structurally different to the auditory hair cells.

Answer 12

they are more clumped together because they aren’t as sensitive to movement,
they also have a kinocilium which are kept through the cell’s life.

Question 13

in the vestibular system there are 2 types of hair cells:

Answer 13

Type 1 – have a calyx on the afferent dendrite that surrounds the hair cells.
Type 2 – across from presynaptic area is an afferent neuron.

Question 14

what is the specific sensory patch where the hair cells are found?

Answer 14

the Macula.

Question 15

the Macula has a striola which divides the structure into 2:

Answer 15

divides it into part dependant on how the hair cells are orientated.

Question 16

what kind of membrane is above the hair cells?

Answer 16

an otolithic membrane that has a otoconia on it.

Question 17

gravity can influence the otoconia and therefore…

Answer 17

can move the otolithic membrane.

Question 18

when the otolithic membrane moves it…

Answer 18

causes displacement of the hair bundles.

Question 19

what structures are in the Ampulla?

Answer 19

there are ampullary crista.

Question 20

what is in the ampullary crista?

Answer 20

the cell bodies of the vestibular hair cells and the afferent fibres are embedded.

Question 21

what is the Ampulla filled with?

Answer 21

endolymph.

Question 22

what does this mean:

the polarity of the hair cells in the ampulla is the same?

Answer 22

all the hair cells are orientated in the same direction.

Question 23

explain:

the semi-circular canals detect angular acceleration?

Answer 23

when head is rotated / angular,
the endolymph in the ampulla moves slightly in the opposite direction,
pushing the cupula,
deflecting the hair bundles,
causing depolarisation or hyperpolarisation.

Question 24

what is the vestibular ocular reflex? (basic)

Answer 24

we are able to read whilst shaking our heads, but can’t read whilst shaking the paper.

Question 25

what allows us to move our extraocular muscles in an opposite to that of the head’s movement.

Answer 25

info link between the vestibular nuclei, the oculomotor nucleus, and the abducens nucleus.

Question 26

what is vestibular nystagmus?

Answer 26

allows the resettling of eye position during sustained to head movement.