Exam 1 (Anatomy & Physiology Review) Flashcards
what is meant by peripheral
Inner ear
Labyrinth & 8th nerve up to the point it enters the brainstem
how many sensory organs are in the peripheral system
5 sensory organs per ear (10 total)
Right ear → utricle + saccule + 3 cristae ampullaris (5)
Left ear → utricle + saccule + 3 cristae ampullaris (5)
what is meant by central
CNS
Brainstem to the cortex
vision denied
no visual target
Eyes closed
Eyes covered
vision allowed
visual target, ability to fixate
Eyes open
Eyes uncovered
Ampullopetal/utriculopetal
endolymph flow towards the ampulla
Ampullofugal/utriculofugal
endolymph flow away from the ampulla
what is the kinocilium
tallest of the sterocilia
Guiding post for other stereocilia to line up by height during embryonic development
Goes away in the cochlea & stays in vestib system
May be able to regenerate hair cells in vestib due to this
More likely to affect the LF outputs before HF
what does this mean
why we might not see things at simpler tasks but can with more difficult tasks
LF = less stimulation/slow
HF = more stimulation/fast
what is presbystasis
vestibular hair cell loss (older, weak calorics, age-related loss over time)
describe the bony labyrinth
outer wall of labyrinth
Filled with perilymph
Similar composition to CSF → high sodium to potassium content
high sodium to potassium content
perilymph
describe the membraneous labyrinth
inside bony
Suspended in perilymph
Inside labyrinth is endolymph → high potassium to sodium content
high potassium to sodium content
perilymph
Sensory epithelia of SCC
cristae ampullaris
Sensory cells within the SCC are the
the cristae and housed in the ampulla (widening of the bony and membranous portion of each canal
what is the ampulla
widening of the bony and membranous portion of each canal
what does sensory epithelia of SCC detect
angular acceleration of the head/body → rotational
what are the sensory cells of the SCC
cristae ampullaris
describe how the SCC are arranged
Arranged orthogonal to each other → they lie at approximately right angles to each other which causes endolymph to flow toward or away from the ampullated end of the canal in at least one canal on each side
Planar orientation for each movement
SCC
pitch
yes
yaw
no
roll
tilting head side to side
Vertical, up and down, sits higher than the others and sits toward the anterior portion of the skull
Roll → tilting head to the side
anterior/superior SCC
what canal is triggered by head side to side
ant
Lays flat to the ground
Lateral to the other arches
Yaw → shaking head no
horizontal/lateral SCC
what canal is triggered by shaking the head no
horizontal/later scc
Vertical
Closer to the foramen magnum
Pitch → shaking head eys
posterior/inferior SCC
what canal is triggered by shaking the head yes
Posterior/inferior SSC
Anterior and posterior canals join together to create
common canal/crus
how do the canals work
They work in a push-pull fashion with the opposite ear
excitatory and inhibitory
They operate bilaterally as a pair
posterior canal shares planes with
contralateral anterior canal
horizontal canals ____ planes
share
why do we tilt for calorics
Horizontal canals are 30 deg tilts
Filled with endolymph and encased in bony tubes
SCC
what is the cupula
gelatinous membrane
Extremely sensitive to motion
explain the density of the cupula
Density is similar to the endolymph to keep it from being sensitive to gravity
Ex: ice cube floating in the water, same density of the stuff around it so it doesn’t influence to gravity
what are the otolithic organs
Gelatinous membrane structures with calcium-carbonate particles/crystals (otoconia/otoliths) embedded on top
what is the sensory epithelia of the otoliths
maculae (aka otoconial membrane)
what does the otolith detect
linear or translational movement including gravitational acceleration and perception of up and down (tilt) relative to gravity
what makes up the otolith
utricle & saccule
Utricle & saccule are _________ to each other
perpendicular
describe the utricle
Superior, larger, oriented horizontally, & sensitive to linear horizontal acceleration and tilt
Large role in postural control & senses changes in orientation with respect to gravity (like moving forward in a car)
describe the saccule
Inferior, smaller, oriented vertically, & sensitive to linear vertical acceleration
No open fluid communication with the utricle or SCC → it is connected through the vestibular aqueduct
Function is controversal but believed to primarily register vertical movements (sensation of going up and down in an elevator)
does the saccule have communication with the utricle and SCC
no
connected thorugh the vestibular aqueduct
what are otoconia
Calcium carbonate particles mixed with protein matrix
ear dust
turn over very slowly during life through a mix of degeneration and turnover
otoconia
sensory cells will continue to respond for as long as the head remains in the same position
true
in otoliths
why is the utricle believed to be the primary sensor for our orientation to gravity and important role in postural stability
because sensory cells will continue to respond for as long as the head remains in the same position
small grain- or rice-shaped particles
otoconia
describe how otoconia cause stimulation in the otoliths
otoconia are small grain- or rice-shaped particles with a density that allows the utricle to respond transiently to linear acceleration and in a more practical fashion to head tilt.
With a sudden forward movement, the supporting structures will move synchronously with the head. Density and weight of them causes them to lag behind the movement of the head
After several seconds of linear forward movement (such as accelerating in a car), the otoconia “catch up” and the utricular response is exhausted
A tilt of the head causes a prolonged response from the utricle
Stimulated by movement (SCC) & position relative to gravity (otolithic)
vestibular hair cells
Each vestibular hair cell has one kinocillium & several stereocilia arranged in a
stair step pattern
Even in a resting state each hair cell has a resting potential
true
Movement causing stereocilia to flow toward the kinocilium
depolarization and increase in electrical potential
Movement causing stereocilia to flow away from the kinocilium
hyperpolarization and decrease in electrical potential
describe hair cell movement in the horizontal or lateral canal
endolymph movement toward the ampulla (ampullopetal) = excitation & movement away from the ampulla (ampullofugal) = inhibition
Excitatory in the direction of the head movement & inhibitory away from the direction of the head movement (ant & post are opposite)
give an example of horizontal canal stimulation
Example w/ head turn to the left → endolymph flows toward the ampulla in left horizontal canal (ampullopetal) and away from the ampulla (ampullofugal) of the right horizontal canal = excitatory response in left labyrinth & inhibitory in right labyrinth
Stereocilia flows toward the kino on the left and away from the kino on the right
Sends asymmetry signal to vestibular nuclei and then passed to the oculomotor nuclei
Left turn → ampullopetal on left w/ stereo toward kino = depolarization & increase in electrical potential (excitatory)
Right → ampullofugal w/ stereo away from kino = hyperpolarization & decrease in electrical potential (inhibitory)
describe hair cell movement in anterior and posterior canals
opposite of horiz
Endolymph flow toward the ampulla (ampullopetal) = inhibition & movement away from the ampulla (ampullofugal) = excitation
Inhibitory in the direction of the head movement & excitatory away from the direction of the head movement
Endolymph flow toward the ampulla (ampullopetal) = inhibition & movement away from the ampulla (ampullofugal) = excitation
ant/post canal
endolymph movement toward the ampulla (ampullopetal) = excitation & movement away from the ampulla (ampullofugal) = inhibition
horizontal/lateral canal
Fluid movement that pushes on the kinocilium first will allow the kinocilium to protect the stereocilia from being sheared, causing
a decrease in neural impulses (inhibition)
Fluid movement that pushes on the shortest stereocilia first will shear/bend the stereocilia that are not being protected by the kinocilium and cause
increased neural firing (excitation)
flask-shaped/test tube with large nerve chalice enveloping the end of the cell (most similar to IHC of cochlea and innervated directly by afferent fibers—mainly afferent function
type I hair cell in otolith
cylindrical/goblet and the most common type (most similar to OHC of the cochlea and innervated directly by efferent fibers –mainly efferent function)
type II hair cell in otolith
otoconia is compressing on hair cells = no stimulation
Head upright
describe hair cell in otoconia with head tilted to the left
shearing and bending of stereocilia away from the kinocilium resulting in inhibition (decrease in firing of afferent fibers)
describe hair cell in otoconia with head tilted to the right
Tilt right → shearing component in the opposite direction and bending toward the kinocilium resulting in excitation and an increase in afferent fibers firing
describe hair cell in otoconia with head tilted forward
shearing and bending of stereocilia toward the kino = depolarization & excitatoin of afferent fibers
describe hair cell in otoconia with head tilted backwards
shearing and bending of stereocilia away from kinocilia = hyperpolarization and inhibition of afferent fibers
what is the striola
Imaginary line through the long axis of each maculae, organizing hair cells
how are hair cells organized in the utricle
oriented toward the striola
how are hair cells organized in the saccule
oriented away from striola
Hair cells are arranged in _______and stereocilia project into otolithic membrane
button-like (macula) sheets
3 Functions of the Vestibular Apparatus
Provide a subjective sensation of movement and/or displacement in the 3-dimensional space
Ex: When the head is tilted in the direction of polarity of a given cell, it depolarizes and excites the afferent fiber. Alternatively, when the head is tilted in the opposite direction, the same cell hyperpolarizes and inhibits the afferent fiber.
To maintain upright body posture (balance)
To stabalize the eyes during head and head and body movement
vestibulo-ocular reflexes
superior portion of the vestibular nerve innervation
utricle, anterior part of saccule(?), and horiz & anterior canals
vestibular nerve cell bodies
scarpa’s ganglion
inferior portion of the vestibular nerve innervation
posterior part of saccule, and posterior canal
VNGs only assess what
lateral canal & first vestibular nerve
Horizontal canal & superior vestibular nerve branch
CN III innervates
superior rectus, inferior rectus, medial rectus, inferior oblique
CN IV innervates
superior oblique
CN VI innervates
lateral rectus
what is the acronym for the muscle CN innervation
LR6 SO4 all the rest are 3
why is it important to evaluate eye movemnet capabilities of PTs
important to evaluate eye movement capabilities of a PT as most all vestibular tests record eye movement as an indirect measurement of peripheral and central vestibular function
what is CN III
oculomotor
what is CN IV
Trochlear
SODA - superior oblique down and away (abduction)
CN VI
abducens
abducts the eye
Detects nodding (“yes”) motion (head tilting forward or backward).
When stimulated, it triggers eye movement downward and inward to stabilize vision.
left anterior canal
Detects head tilting (“ear-to-shoulder”) motion.
When activated, it causes eye movement upward and outward.
left post canal
Detects head turning left or right (“no” motion).
When stimulated, it triggers horizontal eye movement in the opposite direction to maintain visual stability.
left horizontal canal
A shared structure where the anterior and posterior canals merge before entering the vestibular system.
common crus
Reflexive eye movements are equal to but opposite of the head movement → i.e., cancelling response
true
deficit in VOR
oscillopsia, retinal slip
(Like hair cells of cochlea) constant low-level current flowing through hair cells causing resting discharge in vestibular nerve
true
Stimulation towards kinocilium leads to
cell depolarization and increased nerve activity
Stimulation of hair cells away from kinocilium leads to
hyperpolarisation and decreased activity in vestibular nerve
what does VCR stand for
Vestibulocollic Reflex
motor output to the neck
VCR
motor output to the eyes
VOR
motor output to the body
VSR
what does VSR stand for
Vestibulospinal Reflex
what is the VOR
Maintains image stability during head movements by generating reflexive eye movements to counter head motion, preventing blurring or oscillopsia
Reflexive eye movements are equal to but opposite of the head movement → i.e., cancelling response
what does VOR allow for
Allows for gaze stabalization when the head is moving by keeping an image of interest on the fovea of the retina → prevents oscillopsia or visual blurring
what are PT complaints with VOR deficits
Patients will complain of bouncing vision or blurring
what are the limitaitons of the VOR
Limitations: Eyes can only move so far before hitting their limit
When eyes reach their limit, the CNS jerks them back, then slowly moves them in the opposite direction to continue tracking motion - saccades
When the eyes hit their limit again the CNS quickly jerks them back to the center
This cycle of slow eye movement followed by rapid jerking is nystagmus
The slow eye movement happens at the same speed as the body’s turning just in the opposite direction (equal and opposite)
bilateral loss VOR
eye travels with the head on both sides
refixation saccades on both sides
unilateral loss VOR
eye travels with the head on the affected side
refixation saccades on the affected side
no VOR loss
the eye travels opposite the head movement
what is VCR
Vestibular systems connection to stabilization muscles of the cervical spine
Righting reflex
Maintains upright head position & independent of trunk movement
how is VCR mediated
Mediated through otolithic organs & medial vestibulospinal tract
Righting reflex
vcr
Maintains upright head position & independent of trunk movement
vcr
what is vsr
Connection bw vestibular system & muscle stability of torso and lower extremities (below the neck)
how does vsr work
Vestibular system detects movement & postural sway and a corrective signal is sent to the muscles to maintain balance & coordinate movement (can be reflexive or intentional
Vestibular system detects influence of gravity and velocity of head movement
vor
symptoms of VOR dysfunction
Head and eye coordination out of sync
Visual blurring, bouncing (oscillopsia, retinal slip)
Trouble reading signs when walking
Head turns while at a stop or in a grocery store
what is gain
eye movement relative to something else
what are the 6 Types of Mediated Functional Eye Movements
Gaze holding (position maintenance)
Center, up, down, left, right
Saccades
Pursuit/tracking
OPK/OKN
Vergence
Convergence
Divergence
VOR
