BIOL 4380 Lecture Notes - Lecture 9: Otolith, Hair Cell, Endolymph
13 May 2018
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• How are these hair cells arranged in the labyrinth? There are 3 kinds depending on where they
happen to be:
o Saccular macula and utricular macula and the cells in the ampulla.
o The arrows show the orientation of hair bundles in their respective fields.
o In the ambulla, all hair cells are directed in the same direction. The other 2 fields, the
hair cells are arranged in opposite direction.
o The border between the 2 fields is called the striola.
o In the sacculus they face outward, in the utricle they face inwards.
o Do’t eed to ko the relatie orietatios of the superior, posterior, aterior or
inferior.
o Macula = sensory epithelium.
• How are these hair bundles anchored in such a way that the movement of the head produces
…?
o The hair bundles, are surrounded by gelatinous layer called otolithic membrane. On top
of this erae, e hae otooia → ade of hoogeous layer of aliu
aroate rystals. They’re dese ad heay.
o All of this is bathing in the endolymph, much more viscous than the otolithic membrane.
o Do’t eed to ko retiular erae really.
• If we tilt our head a bit, the hair cells that are firmly positioned in your skull, will tilt and the
heavy otoconia is going to drag the hair bundle sin the direction of the tilt. The left side will be
hyperpolarizing and the right will be depolarizing.
• Utricular macula is responsible to sense movements in the horizontal plane. Saccular macula is
responsible for sensing vertical movements.
• The potential created as the result of these movements:
• If e hae oral orietatio of the head, it has a ertai akgroud disharge rate → hair
ells are’t opletely silet, are dishargig at a aselie rate.
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Document Summary
There are 3 kinds depending on where they happen to be: saccular macula and utricular macula and the cells in the ampulla, the arrows show the orientation of hair bundles in their respective fields. In the ambulla, all hair cells are directed in the same direction. The other 2 fields, the hair cells are arranged in opposite direction: the border between the 2 fields is called the striola. On top of this (cid:373)e(cid:373)(cid:271)ra(cid:374)e, (cid:449)e ha(cid:448)e oto(cid:272)o(cid:374)ia (cid:373)ade of ho(cid:373)oge(cid:374)ous layer of (cid:272)al(cid:272)iu(cid:373) (cid:272)ar(cid:271)o(cid:374)ate (cid:272)rystals. They"re de(cid:374)se a(cid:374)d hea(cid:448)y: all of this is bathing in the endolymph, much more viscous than the otolithic membrane, do(cid:374)"t (cid:374)eed to k(cid:374)o(cid:449) reti(cid:272)ular (cid:373)e(cid:373)(cid:271)ra(cid:374)e really. If we tilt our head a bit, the hair cells that are firmly positioned in your skull, will tilt and the heavy otoconia is going to drag the hair bundle sin the direction of the tilt.
