the vestibular system

Question 1

what is the role of otolith organs?

Answer 1

detect linear motion
utricle - left/right or backwards/forwards
saccule - up or down

Question 2

what are the roles of the semicircular canals?

Answer 2

detect head rotation
horizontal canal - turning round
anterior and posterior vertical canals - more complex movements

Question 3

what is the ampulla?

Answer 3

at the end of each semicircular canal, where all the hair cells are located thus where transduction occurs

Question 4

what fluid is present in the organs of the vestibular system?

Answer 4

otolith organs (utricle and ampulla) - endolymph
semicircular canals - endolymph on inside, perilymph outside

Question 5

how does transduction occur in vestibular hair cells?

Answer 5

same principle as hair cells of the auditory system but they respond to lower frequencies (0-20 Hz)

Question 6

how are vestibular hair cells different to auditory hair cells?

Answer 6

vestibular hair cells have more rows of stereocilia and are clumped together, so more resistance to moving them

Question 7

what are the two types of vestibular hair cell?

Answer 7

type I = afferent dendrite forms a calyx (one dendrite surrounds whole cells)
type II = form individual synapses with afferent dendrites

Question 8

how are hair cells activated (linear motion)?

Answer 8

• hair bundles project into gelatinous otolithic membrane, otoconia sit onto of membrane to give it weight
• when you move your head, gravity pulls otoconia in different directions, thus moving membrane, thus moving hair bundles

Question 9

where are hair cells found in otolith organs?

Answer 9

hair cells in utricle are found in a sensory patch called macula, it has a line through it called the striola

Question 10

how are hair cells arranged in otolith organs?

Answer 10

hair cells arranged in different way on each side of striola, while half get excited, other half are inhibited

Question 11

how do semicircular canals detect angular acceleration (rotation)?

Answer 11

• hair cells project into cupula (jelly material)
• as you turn around endolymph moves slower (inertia)
• this inertia of endolymph during rotation displaces the cupula thus exciting hair cells
  occurs in ampulla of semicircular canals

Question 12

how do the semicircular canals on either side of the head work together?

Answer 12

endolymph moves in same direction around the head, so as semicircular canals on one side are activated, the others are inhibited

Question 13

what is the vestibulo-ocular reflex?

Answer 13

reflexive eye movements that helps stabalize vision when head is in motion

shaking head activates horizontal semicircular canals, this pulls eyes back in opposite direction that head is rotating