DPT 540 TEST 2 EXAM QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS GRADED A++
Gaze stability, postural stability, perception of motion
What are the jobs of the vestibular system
Peripheral vestibular structures
Otolith organs, semicircular canals, vestibular nerve
Horizontally, vertically
The maculae of the utricle are oriented in what what? What about the maculae of the
saccule
Otolith organs (saccule and utricle)
Detect linear accleration and head position relative to the pull of gravity. Also detect tilt
and forward/backward motion.
Also has a push-pull arrangement within each otolith organ: with motion to one side,
there is increased afferent discharge from one part of the maculae, while reducing the
afferent discharge from another poriton of the same macula
Semicircular canals
Detect angular acceleration. Horizontal, anterior, and posterior. Arranged at 90 degree
angles to each other. Horizontal canal tipped back 30 degrees from horizontal. The 6 of
these become coplanar pairs and theses planes of the canals are oriented in the same
,planes as the pulling direction of the extraocular muscles which allows connections
between sensory neurons and motor output neurons
Pons
Most vestibular information is first processed where before being largely relayed to the
oculomotor control system, cerebellum, and SC
Maculae
Detect static head position relative to gravity as well as changes in position. Thickened
portion of the utricle and saccule that contain hair cells. Covered by otolithic membrane:
a fibrous and gelatinous structure similar to the capula. Surface fo the membrane
covered with small calcium carbonate crystals: otoconia.
Movement of endolymph relative to the cristae
What allows the detection of angular accleration/deceleration in all three planes?
Bony labyrinth
Consists of SCC, the cochlea, and the vestibule. Filled with perilymphatic fluid
Membranous labryinth
Contain the membranous portions of the SCC, and the otolith organs. One end of each
SCC is widened to form the ampulla. Filled with endolymphatic fluid. Surrounded by
perilymph fluid in the bony labyrinth
The plane of that particular canal
Stimulation of one canal will produce eye movement in what
Sensory redundancy
If damage to one member of the pair, the CNS can still get info from the vestibular
system about head velocity within that plane from the contralateral member
, anatomy of semicircular canals
Membranous, fluid (endolymph) filled tubes. At one end of each canal the tube enlarges
to form the ampulla. Epithelium within the ampulla thickens to form the ampullae crest.
Hair cells are embedded within the ampullae crest.
Hair cells
Projects up in the ampulla and has 40-70 fibers. The kinocillium is the longest and
thickest of the fibers. Fibers are arranged from shortest ot longest. Movement of fibers
toward the kinocillium is excitatory (depolarizing), away from the kinocillium is inhibitory
(hyperpolarizing)
Cupula
Located in ampulla of SCC. Gelatinous cap covering the hair cells. Same density of the
endolymph so it floats in the canal. Accleration of the head leads to cupular
displacement proportional to head velocity.
8th CN
Enters posterior cranial fossa via internal auditory canal. Two main branches- superior
division: innervates anterior and horizontal canal cristae, utricle, macula, and anterior
part of saccule. Inferior division: innervates posterior canal cristae and main part of
sacule. Has a spontaneous firing rate up to 100 spikes/second.
Anterior vest artery
Supplies the vestibular nerve, most of the utricle, and the ampullae of the lateral and
anterior semicircular canals.
Common cochlear artery
Main branch supplies the cochlea
COMPLETE SOLUTIONS GRADED A++
Gaze stability, postural stability, perception of motion
What are the jobs of the vestibular system
Peripheral vestibular structures
Otolith organs, semicircular canals, vestibular nerve
Horizontally, vertically
The maculae of the utricle are oriented in what what? What about the maculae of the
saccule
Otolith organs (saccule and utricle)
Detect linear accleration and head position relative to the pull of gravity. Also detect tilt
and forward/backward motion.
Also has a push-pull arrangement within each otolith organ: with motion to one side,
there is increased afferent discharge from one part of the maculae, while reducing the
afferent discharge from another poriton of the same macula
Semicircular canals
Detect angular acceleration. Horizontal, anterior, and posterior. Arranged at 90 degree
angles to each other. Horizontal canal tipped back 30 degrees from horizontal. The 6 of
these become coplanar pairs and theses planes of the canals are oriented in the same
,planes as the pulling direction of the extraocular muscles which allows connections
between sensory neurons and motor output neurons
Pons
Most vestibular information is first processed where before being largely relayed to the
oculomotor control system, cerebellum, and SC
Maculae
Detect static head position relative to gravity as well as changes in position. Thickened
portion of the utricle and saccule that contain hair cells. Covered by otolithic membrane:
a fibrous and gelatinous structure similar to the capula. Surface fo the membrane
covered with small calcium carbonate crystals: otoconia.
Movement of endolymph relative to the cristae
What allows the detection of angular accleration/deceleration in all three planes?
Bony labyrinth
Consists of SCC, the cochlea, and the vestibule. Filled with perilymphatic fluid
Membranous labryinth
Contain the membranous portions of the SCC, and the otolith organs. One end of each
SCC is widened to form the ampulla. Filled with endolymphatic fluid. Surrounded by
perilymph fluid in the bony labyrinth
The plane of that particular canal
Stimulation of one canal will produce eye movement in what
Sensory redundancy
If damage to one member of the pair, the CNS can still get info from the vestibular
system about head velocity within that plane from the contralateral member
, anatomy of semicircular canals
Membranous, fluid (endolymph) filled tubes. At one end of each canal the tube enlarges
to form the ampulla. Epithelium within the ampulla thickens to form the ampullae crest.
Hair cells are embedded within the ampullae crest.
Hair cells
Projects up in the ampulla and has 40-70 fibers. The kinocillium is the longest and
thickest of the fibers. Fibers are arranged from shortest ot longest. Movement of fibers
toward the kinocillium is excitatory (depolarizing), away from the kinocillium is inhibitory
(hyperpolarizing)
Cupula
Located in ampulla of SCC. Gelatinous cap covering the hair cells. Same density of the
endolymph so it floats in the canal. Accleration of the head leads to cupular
displacement proportional to head velocity.
8th CN
Enters posterior cranial fossa via internal auditory canal. Two main branches- superior
division: innervates anterior and horizontal canal cristae, utricle, macula, and anterior
part of saccule. Inferior division: innervates posterior canal cristae and main part of
sacule. Has a spontaneous firing rate up to 100 spikes/second.
Anterior vest artery
Supplies the vestibular nerve, most of the utricle, and the ampullae of the lateral and
anterior semicircular canals.
Common cochlear artery
Main branch supplies the cochlea
