BIOL 4380 Lecture Notes - Lecture 9: Medial Vestibular Nucleus, Bony Labyrinth, Vestibular Nuclei
13 May 2018
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• Iside of the apulla, thee’s a lae of suppotig epithelial ells ad hai ells, hoee these
hari cells do not rely on any kind of membrane. They rely on cupula to sense displacement.
Cupula is a gelatinous mass which envelopes the hair cell bundle. The cupula seals the canal. The
hair cells are fixed within the cupula. What causes the displacement, is the movement of the
endolymph within the canal as the endolymph moves, it pushes or pulls on the cupula and that
produces the displacement of hair bundles within the cupula.
• The hair bundles all face in the same direction, and the steriocellium face away from the canal.
As the endolymph moves towards the cupula, cupula curves and causes depolarization. In
otolith organs the hair bundles are different, in the ampullae the orientation is the same.
• Fig 14.9 is recording the firing of the afferent coming out of the apulla → the hai ell has a
aselie fiig feue o dishage ate. As e’e aeleatig the spiig aial (oke
on a chair), discharge rate will be faster. The hair cells in the ampulla will stop sensing the
oeet → h e’e ot sesig the eath’s oeet.
o The hair cells in the ampullae sense changes in the rotational movement.
• Extremely important about this system, is that, it works in really close collaboration with all the
other 3 systems: somatosensory system, visual and with auditory system.
• Fig 4., eplais h ou a aitai ou gaze o a ojet as ou head is spiig →
called vestibulo-ocular reflex.
o The neurons innervating both the cochlea and labyrinth have their ganglia in the
Sapa’s gaglia.
o The nucleus called medial vestibular nucleus,
o The next level of neurons are either ascending or descending into the PNS.
o The next level goes to pons, where there is a different nucleus called abducens nucleus.
o The next level is the midbrain.
o The idea is to explain how signals coming from vestibular afferent
o In the medial vestibular nucleus, there are 2 types of fibers, that are being innervated by
the vestibular afferents: some of them become excitatory and some will become
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Document Summary
I(cid:374)side of the a(cid:373)pulla, the(cid:396)e"s a la(cid:455)e(cid:396) of suppo(cid:396)ti(cid:374)g epithelial (cid:272)ells a(cid:374)d hai(cid:396) (cid:272)ells, ho(cid:449)e(cid:448)e(cid:396) these hari cells do not rely on any kind of membrane. Cupula is a gelatinous mass which envelopes the hair cell bundle. The hair cells are fixed within the cupula. As the endolymph moves towards the cupula, cupula curves and causes depolarization. In otolith organs the hair bundles are different, in the ampullae the orientation is the same. Fig 14. 9 is recording the firing of the afferent coming out of the a(cid:373)pulla the hai(cid:396) (cid:272)ell has a (cid:271)aseli(cid:374)e fi(cid:396)i(cid:374)g f(cid:396)e(cid:395)ue(cid:374)(cid:272)(cid:455) o(cid:396) dis(cid:272)ha(cid:396)ge (cid:396)ate. As (cid:449)e"(cid:396)e a(cid:272)(cid:272)ele(cid:396)ati(cid:374)g the spi(cid:374)(cid:374)i(cid:374)g a(cid:374)i(cid:373)al ((cid:373)o(cid:374)ke(cid:455) on a chair), discharge rate will be faster. Fig (cid:1005)4. (cid:1005)(cid:1004), e(cid:454)plai(cid:374)s (cid:449)h(cid:455) (cid:455)ou (cid:272)a(cid:374) (cid:373)ai(cid:374)tai(cid:374) (cid:455)ou(cid:396) gaze o(cid:374) a(cid:374) o(cid:271)je(cid:272)t as (cid:455)ou(cid:396) head is spi(cid:374)(cid:374)i(cid:374)g called vestibulo-ocular reflex: the neurons innervating both the cochlea and labyrinth have their ganglia in the.
