A&P vestibular Flashcards
During a lifetime what percentage of adults experience dizziness
40%
What percentage of adults experience dizziness over the age of 60
60%
Vestibular rehabilitation includes specific exercises and/or
repositioning maneuvers designed to:
decrease dizziness
increase balance function
increase general activity levels
Exercises are designed to
promote CNS compensation for vestibular system hypofunction
repositioning maneuvers are used to
remove otoconia from semicircularcanals of the inner ear.
What is Anatomical Overview process
input (Visual Somatosensory Vestibular) >Processing (Vestibular Nuclear Complex Cerebellum)> output (Vestibular Ocular Reflex Vestibular Spinal Reflex)
Strong Inhibitor
of vestibular and somatosensory systems
Neurological Pathways
medial longitudinal fasciculus ( MLF)
Dieter’s tract
Visual Cranial Nerve Examination
sensory: vision test
motor: smooth pursuit test
Fastest System compared to visual and vestibular systems
Neurological Pathway
spinothalamic tract
dorsal column medial lemniscal tract
Sensory Receptor Examination
tactile awareness
kinesthetic awareness
proprioceptive awareness
Vestibular System Purpose:
head and body orientation
Conflict Resolver: of the 3 systems
Vestibular System Components
Vascular Supply: labyrinthine artery Nerve Supply: CN VIII Bony Labyrinth: Temporal Bone Membranous Labyrinth: Anterior,Posterior,and Horizontal Semicircular Canals(SCC) Utricle and Saccule (Otoliths)
Bony Labyrinth: contains what
Temporal Bone contains perilymph (high Na:Kratio); supports the membranous labyrinth
MembranousLabyrinth: contains what
SCC’s contain endolymph (high K:Na ratio);
Utricle and Saccule (Otoliths) contain endolymph and otoconia (calcium carbonate crystals)
SCC’s have a greatest sensitivity
greatest sensitivity to angular motions (rotation, flexion, extension, lateral tilt);
Why do SCC’s have a greatest sensitivity have a greatest sensitivity to angular motions
orthogonally positioned to one another; function in co-planar pairs (left anterior/right posterior; right anterior/left posterior; left horizontal/right horizontal)
Otoliths have a greatest sensitivity to
to linear motions (up, down, forward, backward)
Why do Otoliths have a greatest sensitivity to to linear motions
otoconia (calcium carbonate crystals) giving them mass
What is meant by PUSH:
The resting neural firing rate of the vestibular nerves are 60-100 pulses per second. When the small steriocilia are “pushed” towards the large kinocilium, that hair cell is depolarized and the frequency of action potential increases.
What is meant by PULL:
The resting neural firing rate of the vestibular nerves is 60-100 pulses per second. When the small steriocilia are “pulled” away from the large kinocilium, that hair cell is hyperpolarized and the frequency of action potential decreases.
What is the PUSH-PULL:
Head moves angularly (rotation, flexion, etc…) vestibular nerves on one side of the head are “pushed” and the others are “pulled”. SCC co-planar pairs report to the VNC to determine which direction the head is moving.
What neurologically is happening For PUSH PULL
Push -Depolarization
Pull -Hyperpolarization
If head turns to the right where is the push and pull coming from
The RIGHT Pushes or Depolarizes
The LEFT Pulls or Hyperpolarizes
Primary Processing: occurs in the
vestibular nuclear complex (VNC) which is located between the pons-medulla and cerebellum
Adaptive Processing: occurs in the
cerebellum and largely has a dampening or inhibitory effect on the vestibular system
Vestibular Ocular Reflex (VOR) role is
maintains gaze stability while head is moving
What is normal VOR
gain is = 1; meaning there is an equal but opposite head-to-eye ratio; for every 1 degree the head moves left, the eyes move 1 degree right via the VOR; this provides clear dynamic vision
Vestibular Spinal Reflex (VSR)
maintains postural stability
VOR neural pathways.
facillitory (depolarization)
inhibitory (hyperpolarization).
If the head is rotating right and the VOR is driving the eyes
left, Follow the pathways from the horizontal SCC’s to the extra ocular eye muscles.
What are the 3 input systems driving postural stability and dynamic visual acuity
Visual System • strongest • sensory and motor Somatosensory System • fastest • tactile/kinesthetic/proprioceptive awareness Vestibular System • conflict resolver of the 3 systems • purpose: head and body orientation)
2 primary reflexes responsible for postural stability and dynamic visual acuity?
Vestibular Ocular Reflex
• Maintains gaze stability while head is moving for clear, dynamic vision
• For every 1 degree that head moves in one direction, the eyes will move 1 degree in the opposite direction
Vestibular Spinal Reflex
• Communicates with muscles for stability to maintain postural stability
How do semicircular canals differ from the otoliths
They differ from otoliths in that otoliths are the most sensitive to linear motions (up, down, forward, backward) while the semicircular canals are the most sensitive to angular motions (rotation, flexion, extension, lateral tilt).
How many semicircular canals are there in the human head
There are 6 semicircular canals in total with three in each ear. It is these 6 SCC’s that function in co-planar pairs such as left anterior/right posterior; right anterior/left posterior; left horizontal/right horizontal. They are membranous rather than bone.
Which cranial nerves are responsible for eye movement and what are their actions?
Cranial nerve III (Oculomotor nerve) – Responsible for eyeball movements up, down, medially, and laterally
Cranial nerve IV (Trochlear nerve) – Responsible for lateral and downward eyeball movements
Cranial nerve VI (Abducens nerve) – Responsible for lateral deviation of the eyeball
CN III = up, down, in
CN IV = down and in (intorsion)
CN VI = out
