Vestibular
Anatomy & Function
NBIO 401 – Monday November 4, 2013
Objectives:
-Be able to describe the structure of the two components of the
vestibular system, the semicircular canals and the otoliths.
-Be able explain how the structure of the semicircular canals
and the position and orientation of the hair cells in the ampulla
allow the canals to transduce head rotation into neural signals.
-Be able explain how the structure of the otoliths and the
position and orientation of the hair cells in the saccule and
utricle transduce head tilt and linear acceleration into neural
signals.
-Be able to describe the pathway from the vestibular labyrinth
in the periphery to the vestibular nuclei, including the locations
of neuron cell bodies and axon terminations.
Objectives:
-Be able to describe the structure of the two components of the
vestibular system, the semicircular canals and the otoliths.
-Be able explain how the structure of the semicircular canals
and the position and orientation of the hair cells in the ampulla
allow the canals to transduce head rotation into neural signals.
-Be able explain how the structure of the otoliths and the
position and orientation of the hair cells in the saccule and
utricle transduce head tilt and linear acceleration into neural
signals.
-Be able to describe the pathway from the vestibular labyrinth
in the periphery to the vestibular nuclei, including the locations
of neuron cell bodies and axon terminations.
Objectives:
-Be able to describe the structure of the two components of the
vestibular system, the semicircular canals and the otoliths.
-Be able explain how the structure of the semicircular canals
and the position and orientation of the hair cells in the ampulla
allow the canals to transduce head rotation into neural signals.
-Be able explain how the structure of the otoliths and the
position and orientation of the hair cells in the saccule and
utricle transduce head tilt and linear acceleration into neural
signals.
-Be able to describe the pathway from the vestibular labyrinth
in the periphery to the vestibular nuclei, including the locations
of neuron cell bodies and axon terminations.
Objectives:
-Be able to describe the structure of the two components of the
vestibular system, the semicircular canals and the otoliths.
-Be able explain how the structure of the semicircular canals
and the position and orientation of the hair cells in the ampulla
allow the canals to transduce head rotation into neural signals.
-Be able explain how the structure of the otoliths and the
position and orientation of the hair cells in the saccule and
utricle transduce head tilt and linear acceleration into neural
signals.
-Be able to describe the pathway from the vestibular labyrinth
in the periphery to the vestibular nuclei, including the locations
of neuron cell bodies and axon terminations.
Vestibular Labyrinth:
-semicircular canals
-otoliths
SEMICIRCULAR
CANALS
SEMICIRCULAR
CANALS
HOLLOW
HOOP
(CANAL)
SEMICIRCULAR
CANALS
HOLLOW
HOOP
(CANAL)
WIDER CHAMBER
IN CANAL
(AMPULLA)
SEMICIRCULAR
CANALS
(ROTATION)
SEMICIRCULAR
CANALS
(ROTATION)
OTOLITHS
(TILT & ACCELERATION)
SEMICIRCULAR
CANALS
(ROTATION)
OTOLITHS
(TILT & ACCELERATION)
Semicircular Canals
(ROTATION)
SEMICIRCULAR
CANALS
HOLLOW
HOOP
(CANAL)
WIDER
CHAMBER
(AMPULA)
AMPULA
AMPULA
AMPULA
UTRICLE
AMPULA
Position of semicircular canals in the skull
Otoliths
(TILT, ACCELERATION)
OTOLITHS
(TILT & ACCELERATION)
OTOLITHS
(TILT & ACCELERATION)
Kinocillium
(longest process; at one side)
Stereocilia
(all shorter processes)
Kinocillium
(longest process; at one side)
HAIR CELLS IN OTOLITHS
Otoliths
HAIR CELLS IN OTOLITHS
Otoliths
HAIR CELLS IN OTOLITHS
Otoliths
Bending processes
toward kinocillium
DEPOLARIZES
Bending away from
kinocillium
HYPERPOLARIZES
Orientation of the maculae of the utricle and saccule
Fitzpatrick, R. C. et al. J Appl
Physiol 96: 2301-2316 2004;
doi:10.1152/japplphysiol.00008
.2004
Copyright ©2004 American
Physiological Society
Orientation of the maculae of the utricle and saccule
Fitzpatrick, R. C. et al. J Appl
Physiol 96: 2301-2316 2004;
doi:10.1152/japplphysiol.00008
.2004
Copyright ©2004 American
Physiological Society
Central Connections
of the
Vestibular Labyrinth
Pathway from the canals
and otoliths to the brain is
via axons whose cell
bodies are in a ganglion
(called Scarpa’s ganglion
or the vestibular ganglion).
Scarpa’s
Ganglion
(vestibular
ganglion)
May 9, 1752 –
October 31, 1832
Carlo Beolchin
(Scarpa’s student)
Museo per la storia dell ‘Universita de Pavia
Museo per la storia dell ‘Universita de Pavia
Museum for the history of the University of Pavia
Museo per la storia dell ‘Universita de Pavia
Museum for the history of the University of Pavia
Scarpa’s
Ganglion
(vestibular
ganglion)
The proximal end of the axons of neurons in Scarpa’s ganglion
terminate in the vestibular nuclei.
inferior
cerebellar
peduncle
V
VIIIth
nerve
vestibular
nuclei
inferior
cerebellar
peduncle
VIIIth
nerve
Vestibular nuclei project to:
1) spinal cord
2) oculomotor nuclei
3) reticular formation
4) cerebellum
5) thalamus
Alcohol and Dizziness
Normally, the cupula has neutral
buoyancy in endolymph that
surrounds it.
Alcohol is less dense than water (see
demo to right). When you drink,
alcohol enters the blood, and then into
the cupula. The cupula becomes less
dense. It floats in the endolymph
more. The cupula bends a little more
than usual away from the ground.
This bends hair cells, as if you are
rotating, even when you are still. This
gives you the sensation of rotating
when you are still, i.e., you get the
dreaded spins.
Blue H2O cubes float in water (left) but sink in
alcohol (right)
the end