Auditory 2 Flashcards
What are the 3 systems required for proper balance? (functioning of motor activities, eye movements, & posture)
- Vestibular System
- Visual System (least reliable)
- Prioreceptive
-no vestibular = nausea &vomiting ( position of head & body in space)
What is within the bony labyrinth? Membranous labyrinth?
- Perilymph (bony)
2. Endolymph(membranous)
What are the 2 otolyphic organs?
- Utricle (horizontal)
2. Saccule (vertical movement)
Where is the vestibular system located in the skull?
in the petrous part of the TEMPORAL bone
- lateral to the internal acoustic meatus (along w/ cochlea)
The bony & membranous labyrinths of vestibular system are continuous with the Auditory system: TRUE OR FALSE
- what fluids are in each?
TRUE
- Bony = PERILYMPH
- Membranous = ENDOLYMPH
What are the 3 main divisions of the vestibular system? Which two are otolithic organs? What movement do each serve?
- Semicircular canals (circular motion)
- Utricle - horizontal
- Saccule - verticle
UTRICLE & SACCULE are otolithic organs
(semicircular canals just have endolymph)
What fluid is essential for the creation of receptor potentials? What are the primary receptors in the Vesitbular (and auditory) system?
- ENDOLYMPH
2. Hair cells
What organ of the vestibular system uses the MLF to coordinate movements of the eye w/ head & neck?
SEMICIRCULAR canals
- use CN 3,4,6
Which vestibular organ is the primary gravity & acceleration sensor?
UTRICLE
Where are the hair cells in the semicircular canals located in? What is the gelatinous substance that covers the hair cells?
- AMPULLA of the canal (ampulary crest & cupola)
2. CUPOLA
If the head moves to the right, which direction does the cupola move? What is this called?
- Cupola moves LEFT (opposite)
2. INERTIAL DISPLACEMENT of the fluid & cupola - bends hair cells
The inertial displacement is an acceleration force or a velocity?
ACCELERATION
but considered velocity
What occurs when the sterocilium move towards the kinoocilium? AWAY?
- DEPOLARIZATIOn (K+ in)
- HYPERPOLARIZATION
- K+ influx
- depolarization
- calcium released
- NT released
- Bipolar cells FIRE AP
What fires action potentials, hair cells or bipolar cells?
BIPOLAR CELLS
The greater the difference in INERTIAL DISPLACEMENT = the greater _____
greater perceived “velocity”
actually acceleration, but perceived as velocity
If the head is moving counterclockwise, which direction does the fluid on the left & right move in the horizontal canals?
LEFT: moves OPPOSITE
- clockwise (TOWARD KINOCILIUM)
= increase FIRING!!!
RIGHT: moves counterclockwise
- AWAY from kinocilium = decrease in firing
The anterior canal on right is paired with ____ canal on left.
The posterior canal on right is paired with the ____ canal on the left.
Which canals are paired?
- Posterior canal on left
- Anterior canal on left
HORIZONTAL CANALS ARE PAIRED
If there is an infection, or if one canal in a specific plane stops working, this is perceived as____
MOVEMENT
- increase in K+
What has a tonic output in the vestibular system? As long as this cancels out on both sides, the brain perceives it as NO MOVEMENT
vestibular Nerve
so that the decrease or increase in K+ can be sensed by the vestibular system
Because the saccule & utricle contain OTOLITHIC granules (calcium carbonate), this allows them to respond to what?
GRAVITY
- granules have weight
Where are the auditory hair cells located?
Organ of Corti on a thin basilar membrane in the COCHLEA of the inner ear
Which organ (SSC, utricle or saccule):
- detects upright position & head tilt
- is the primary gravity sensor
- HORIZONTAL linear acceleration
UTRICLE!!!
Which organ (SSC, utricle or saccule):
- Detects general orienttion
- VERTICAL linear acceleration
SACCULE
Describe the pathway of INPUT TO CNS from the hair cell to the vestibular nuclei:
- Hair cell
- Bipolar Cell (AP!!)
- Vestibular GANGLION
- CN 8
- Vestibular Nuclei
There are 2 divisions of the vestibular ganglion, what structures are located superiorly and what is inferior?
SUPERIOR:
- UTRICLE
- anterior SACCULE
- horizontal & anterior SSC
INFERIOR:
- posterior Saccule
- posterior SSC *****
Where is the vestibular nuclei? The cochlear?
Vestibular is medial to ICP
- Cochlea is the saddle bag of ICP
How many vestibular nuclei are there?
4
Which fibers of the MLF (ascending/descending) control eye movements? Head and neck movements?
eye = ASCENDING MLF
head & neck = DESCENDING MLF
Which nuclei projects to the cerebellum & coordinates balance with voluntary movement?
INFERIOR Nuclei
What two structures is the vestibulocerebellum associated with? Where does it receive DIRECT input from?Indirect?
- Flocculondular lobe
- Vestibular nuclei
- from SCC, utricle & saccule (direct = IMMEDIATE RESPONSE)
- indirect = Vestibular nuclei, Lateral Geniculat, Superior Colliculus, pontine nuclei
Output of the cerebellar influences is projected back to what?
VESTIBULAR NUCLEI
- control axial & proximal limb muscles for BALANCE & POSTURE
- eye movement, head & neck
(vestibular to cerebellum & then cerebellum back to vestibular)
The Lateral Vestibulospinal Tract originates from what nucleus? Where does it project to? Which muscles?
- LATERAL VESTIBULAR NUCLEUS
- ENTIRE LENGTH OF CORD (ventral funiculus)!!!!
- PROXIMAL LIMB MUSCLES (extensors)
The MEDIAL Vestibulospinal Tract (DESCENDING MLF) originates from what nucleus? Where does it project to? Which muscles?
- Medial Vestibular Nucleus
- CERVICAL SPINAL CORD ONLY!!!!!!
- NECK MUSCLES!
(makes sense to only be cervical spinal cord)
What are the 2 primary afferent pathways of the Vestibular system?
- Vestibular Nuclei
2. Floccolondular lobe
What are the 4 SECONDARY Vestibular connections of the Vestibular system?
- Cerebellum
- Spinal cord
- Brainstem (ascending MLF, RT)
- Thalamic & Cortical
What are the 5 types of eye movements?
- Vestibulo-occular reflex
- Optokinetic response (nystagmus)
- Smooth pursuit
- Saccadic eye movement
- Mergence Eye movement
What is the RAPID, CATCH UP eye movement called? Is it reflexive?
SACCADIC
- yes, reflexive and PRE-PROGRAMMED
What is the voluntary eye movement requiring a moving stimulus?
SMOOTH PURSUIT
What is vergence?
Eyes converge on near objects, diverge on far objects
Which eye movement requires the visual/cerebral cortex?
SMOOTH PURSUIT (because it is voluntary***)
What type of movement stabilizes the image on the retina during rotation of head?
VOR
- Vestibulo-occular
(VOR rotates opposite to the side the head is rotating)
How does the visual system attenuate?
through the Vestibule-Ocular Reflex ***
-tonic activation via nuclei of 3rd and 6th nerve
If the head is moving to the RIGHT, and both eyes begin to move left what occurs in the VOR reflex?
- Head right
- Right horizontal canal activated
- RIGHT vestibular nucleus
- LEFT 6th nucleus (lateral rectus on left)
- RIGHT 3rd nucleus contract the RIGHT medial rectus
- BOTH EYES MOVE LEFT
What is nystagmus? How is it tested clinically?
rhythmic back & forth movement of the eyes
- SMOOTH & SACCADIC movement
- tested by the caloric test; COWS
Cold water = nystagmus OPPOSITE
WARM = same side
How do we get dizzy:
1. spinning with eyes closed & suddenly open eyes
(copula returns to baseline )
- Looking out a car window when an adjacent car moves away
- in the cabin of a boat during a storm (motion sickness)
- looking at the horizon to minimize this affect
- Vestibular input w/o vision
- Sense of motion through visual system w/o VESTIBULAR CONFIRMATION
- Sense of motion through visual system w/o VISUAL confirmation
A virus invades the stria vascularis cells of the left inner ear, resulting in a significant increase in the concentration of potassium in the endolymph. Which one of the following would you expect to happen?
a) The outer hair cells hyperpolarize, causing a high pitched “ringing” in the ears.
b) The patient complains of muffled sounds due to smaller receptor potentials in the inner hair cells.
c) The hair cells in the left ampulae depolarize to a greater extent than those on the right, and the patient complains of vertigo/dizziness.
d) The otoconia hyperpolarize, and the patient feels “light-headed.”
c)The hair cells in the left ampulae depolarize to a greater extent than those on the right, and the patient complains of vertigo/dizziness.
When you voluntarily turn your head to the left, which one of the following events will occur in the vestibular system?
a) Kinocilia in the ampullae of all the semicircular canals will be simultaneously activated.
b) Movement of the stereocilia in the left horizontal canal move towards the kinocilia, resulting in depolarization of the hair cell.
c) The medial and superior vestibular nuclei will be inhibited by the afferent fibers from the semicircular canals.
d) The velocity of the movement is detected by the otolithic granules in the anterior and posterior semicircular canals.
e) Compensatory eye movements will likely be inhibited by the descending MLF.
b) b) Movement of the stereocilia in the left horizontal canal move towards the kinocilia, resulting in depolarization of the hair cell.
Vestibular function is tested in a 19-year-old man using the caloric test. Assuming a normal outcome, which one of the following is most likely to occur when WARM water is introduced into the man’s RIGHT ear?
a) Horizontal nystagmus, fast phase directed left.
b) Horizontal nystagmus, fast phase directed right.
c) Occular counter-roll (eversion of eyeball) to the right.
d) Vertical nystagmus, fast phase directed downward.
e) Vertical nystagmus, alternating fast phases.
COWS
b) Horizontal nystagmus, fast phase directed right.
