vestibular system

Question 1

Utricle and saccule

otolith organs

Answer 1

used for near motion i.e. moving forwards/sideways/head tilts

Utricle horizontal e.g. in a car

saccule vertical e.g. in a lift

Question 2

utricle horizontal

Answer 2

e.g. in a car

Question 3

3 different semi circular canals

Answer 3

anterior vertical
posterior vertical
horizontal (spinning)

Question 4

excitation of one side of the head

Answer 4

will inhibit the other side to know where you are

Question 5

ampulla

Answer 5

sensory structures e.g. hair cells transducing the motion into electrical signal

bulge along the canal

Question 6

cell bodies

Answer 6

found in scarpa’s ganglia

there are about 20,000 auditory vestibular axons on each side of the head and they cell bodies lie in scarpa’s ganglion

Question 7

endolypmh

Answer 7

fluid that fills vestibular labyrinth
unusual extracelluar fluid in that it has ionic concentrations similar to intracellular fluid

high K+ and low Na+

Question 8

perilymph

Answer 8

fluid in the scala vestibuli and scala tympani

ionic content similar to CSF
low K+ and high na+

Question 9

when angle of head changes or when head accelerates

Answer 9

a force is exerted on the otoliths;
this exerts force in the asme direction on the gelatinous cap
which moves slightly
and the cilia of the hair cells bend.

not just any defection will do

echoer cell has one especially tall cilium (the kinocilium)
the bending of the hair towards the kinocillium resulting in depolarisation of excitatory receptor potential

bending the hairs along the other direction of the kinocilium hyper polarises and inhibits the cell

if hairs are perpendicular to their preferred direction, they barely respond

Question 10

the sacular maculae (sensory epithelium) are orientated …

Answer 10

more or less vertically

Question 11

the utricular maculae is orientated …

Answer 11

mostly horizontally

Question 12

2 types of vestibular hair cell

Answer 12

type 1 - massive expanding afferent nerve fibre around bottom of hair cell

type 2 - smaller normal afferent nerve fibre at bottom of hair cell

functionally the same
don’t know why there are two different ones yet

Question 13

describe saccule and utricle detecting head tilt and linear acceleration

Answer 13

Hair cells project onto otolithic membrane (jellly)
On top on this is otoconia (crystals of calcium carbonate)
More dense and response to changes in gravity differently to hair cells beneath it
Because dense they move down with gravity and pulls the jelly with it and the hair cells stuck into it exciting them

Question 14

the cupula

Answer 14

s a gelatinous structure penetrated by hair bundles

Question 15

angluar acceleration

Answer 15

rotation

Question 16

the inertia of endolymph during rotation displace cupula

Answer 16

The endolymph is slower to move than the rest of the head
(so seems like it moving in opposite direction)
Pushing gelatin of cupula pushing hair bundles in one direction or the other

Question 17

when drunk and lie down

Answer 17

Alchol absorbs into the cupula faster than the endolymph which gives the illusion of spinning
Gradually even out over night
And then in the morning the endolymph will be less sense than the cupola

Question 18

semi-circular canals on either side of the head work in pairs

Answer 18

Horizontal canals on both sides lie in roughly the same plane so can act as a functional pair.
The anterior canal on one side lies in parallel with the posterior canal on the other side so acts as a functional pair.

Question 19

semi-circular canals on either side of the head work in pairs

Answer 19

Horizontal canals on both sides lie in roughly the same plane so can act as a functional pair.
The anterior canal on one side lies in parallel with the posterior canal on the other side so acts as a functional pair.

Question 20

vestiubular nystagmus

Answer 20

enables the resetting of eye position during sustained head rotation

Question 21

meniere’s disease

Answer 21

Poorly understood, spontaneous condition
No definitive cause
Potentially due to excessive endolymph

Intermittent, relapsing vertigo (spinning feeling)

Can be accompanied by tinnitus and distorted hearing (due to endolymph also existing in the cochlea)

Question 22

treatment for menieres disease

Answer 22

diuretics (decrease the amount of endoymph), sedatives, steroids (hit and miss)

Question 23

extreme treatment

Answer 23

remove the labyrinth or destroy vestibular hair cells (certain antibiotics can enter hair cells (via potassium channel) aminoglycocide, and kills them)

Question 24

hair cells in the vestibular system are similar to that of the auditory system but

Answer 24

they respond to lower frequencies (0-20 hz)