Vestib: Peripheral Anatomy Flashcards
List the vestibular symptoms that impact function
- Dizziness
- Vertigo
- Imbalance
- Visual fatigue/blurring
- Headache
What is the prevalence of dizziness?
*#1 complaint for those over 65
*42% of people describe feeling of dizziness in their lifetime
*85% of dizziness is peripheral
What is the purpose of the vestibular system?
- Allows for maintenance of gaze stability with head movement such as the detection of head angular velocity and linear acceleration
- Provides reflexive information for maintaining upright posture to help orient the head and body to gravity
- Support the spatial perception and orientation of the body
What is order of convergence for sensory input?
- Sensory
- Integration
- Motor input
- Balance
What falls under sensory inputs?
- Vestibular
- Visual
- Proprioceptive
What falls under integration of input?
- Cerebellum
- Cerebral Cortex
- Brainstem
What falls under motor input?
- Vestibulo-ocular reflex
- Motor impulses for eyes
- Motor impulses for postural adjustments
What are the two labyrinths in the cochlea?
- Bony
- Membranous
What is the SSCs covered in?
Bony labyrinth
Which structures of the vestibular system is housed within the membranous labyrinth?
- Perilymph
- Endolymph
- SSCs duct
- Ampullae
The membranous portion suspend into ___ and it is filled with _____
Perilymph & Endolymph
What are the peripheral boundaries:
- OE: ____ to ___
- ME: ____ to ___
- IE: ____ to __
- Pinna to TM
- TM to Oval window (stapes)
- Oval window to VIIIth nerve
What are the vestibular End-organs?
- 3 SSCs
- 2 otoliths
What are the central processors?
- Brainstem
- Cerebellum
What does the vestibular apparatus house?
- Utricle
- Saccule
- SSCs ducts
List the orientation of the 3 SSCs and their degrees
- Anterior/Superior = Sagittal Plane (Nodding) – 45
- Horizontal/Lateral = Transverse Plane (rotating) – 30
- Posterior/Inferior = Frontal plane (bending) – 45
Which liquid is the ampulla, crista ampullaris, and cupula housed in?
Endolymph
What is the pairing of the contralateral SSCs duct when they are oriented in the same plane?
- Right Superior –> Left Posterior
- Left Superior –> Right Posterior
- Left Horizontal –> Right Horizontal
LARP v RALP
For the SSCs, where are the HCs embedded?
Cupulla
List the process for when the HCs bends in the opposite direction of rotation & linear.
- Ion channels open
- HCs depolarize and increase the firing of afferent fibers
- Rotational velocity equalizes and the cupula is back to an upright position
- The membrane potential of the cell normalizes
List the process for when the HCs bends in the same direction of rotation and linear.
- Ion channel closes
- HCs hyperpolarized and causes a decrease in reduction of the afferent nerve firing
- Cupula is back in upright position
- Membrane equalizes
What does Type I HC focus on?
Phasic; fires when moving
What does Type II HC focus on?
Tonic; fires all the time to help us know where we are in space
What does the SSC stimulation detects?
Angular velocity of the head
What are some advantages of the SSC stimulation?
- Allows for sensory redundancy if a pathology of one of the SSC duct occurs
- “Common mode rejection” - the simultaneous firing of both SSC ducts of the pair is ignored by the CNS
- Phsyiologic layout allows for compensation for sensory overload
What are the divisions of the vestibular nerve and where does each division send information to?
- Superior Branch = Utricle, Horizontal & Anterior SCCs
- Inferior Branch = Saccule & Posterior SCC
Where does the vestibulocochlear travel past?
Cerebellopontine angle
Where does the vestibulocochlear travel enter into?
Brainstem at pontomedullary junction
What is the resting firing rate of the vestibular nerves?
70-100Hz
When excited, what happens with the hair cells?
They bend towards the kinocilium and firing rate increases
When inhibited, what happens to the hair cells?
Bend away from kinocilium and firing rate decreases
What are the primary output centers of the central processing of the vestibular input?
- Vestibular Nuclear Complex
- Cerebellum
Where is the Vestibular Nuclear Complex (VNC) located?
Rostral medulla and caudal pons
What is the role of the VNC?
Relay center for vestibular information
List the four VN’s and where they project to
- Lateral VN = Utricle & Saccule
- Superior VN + Medial VN = SCCs
- Inferior/Dorsal = Other nuclei + Saccule
Explain velocity storage system
Is when the CNS converts the small time constant response at the canal afférents to the long time constants response found at the level of the VN
If it extends 5.7s there’s disequilibrium in the system if the energy stored is not the same
