OS III, EX II, Vestibular system Flashcards
Where is the vestibular system located?
Within the petrous portin of the temporal bone
what structures make up the vestibular system?
the bony labrynth and the membranous labyrinth
What is the bony labrynth subdevided into?
vestibule and semiciruclar canals
What is the membranous labrynth?
tube containing receptors for head movement
What is membranous labrynth subdivided into?
semicircular ducts and the saccule and uricle which are in the vestibule
What secretes endolymph?
cochlear ducts
how does endolymph drain?
into the dural sinuses via endolymphatic duct
What secretes perilymph?
periosteum
Where and how does perilymph drain?
drains into VCF via the perilymphatic duct
So were does both the perilymph and endolymph end up?
the sinuses, because CSF will resob into sinuses
What is meniere’s disease?
Transient vertigo and dissiness, nausea, eyemovements ets causes by excess endolymph secretion and fluid pressure
What are the three semicircular ducts?
Located in the temporal boneanterior, horizontal and posterior
How are the semicircular ducts arranged?
mutually perpendicular
How are the ducts named?
anterior is closer to face, horizontal is on bottom to side and post is pointing more to the back.
What are crista?
receptors
Where are the crista?
ampulla of each semiciruclar canal
what makes up the gelatinous mass?
epithelium of receptor hairs and supporting cells
What do the hair cells have?
single kinocilium (tallest hair bith something on top) and stereocilia that are projecting into the gelationus mass
what motions are the hair cells most sensitive to?
angular acceleration
when head turns, what happens to endolymph?:
its stays in place due to inertia causing a friciton
what convesy the net direction of head movements?
vestibbular activity, current through each loop
what would trigger an action potiential in vestibular nerve?
hair cells.
What is the macula?
Part of the receptor system, similar to the christa but with more hairs and otolith layer on top
what is an otoliths?
calcium barbonate stones embedded in a gelatinous layer
What are the two cilia types on hair cells?
Kinocilium and steriocilia
What are the layers of the macula?
neurons into macular hair cells, cilia into gel, otoliths on gel
How are the maculas of the utricle and saccule oriented?
at right angles to each other, Macula-verticle, Uricle - horizontal
when would hair cells have the higher fireing weight, depolarization?
When steriocilia are deflected toward the kinocilium
What happens when steriocilia go away from kinocilium?
Inhibition and hyperpolarization
what causes hair cells to bend?
the gel full of otoliths moves, taking hair with it.
What can distort receptors directly without endolymphatic movement.
linear acceleration
What can distort hair receptors?
inertia of otoliths and gravity on otolyths
What determines what receptor cells are affected?
directon of movement
Neurons from where make up vestibular nerve?
semicircular canals, saccule and utricle
What can cause virtigo?
menieres disease or acoustic neuroma
what is virtigo?
disorientation and a sense of spinning leading to a loss of equilibrium
what is acoustic neuroma?
benign tumor of myelin forming cells of inferior vestibular nerve.
What does acoustic neuroma cause for hearing?
Ispilateral sensorineural deafness or tinnitus
What is the vestibular distrubance caused by acoustic neuroma?
unstable gait, vertigo, nausea, vomiting,
What nerve gets compressed with acoustic neuroma?
often the facial nerve gets compressed but it doesn?t seem to cause symptoms, ie loss of facial expression
What is benign paroxysmal positional vertigo?
Vertigo caused by otolyths falling from utricle into the canals that trigger motion in the crista.
How would an otolyth get dislodged?
head injury, infection, degeneration with age
Vestibular activity via the vestibular nerve goes where?
Vestibular nuclei and vestibulo-cerebellum
Role of vestibular nucleui in brain stem?
Project to thalamus ans cortex, spinal cord for poetural control, brain stem nuclei for eye movements and autonomic centers for vasucalr control
Role of vestibulo-cerebellum ?”
sends processed info back to vestibular nuclei, facilitates vestibular reflexes
What regulates posture control?
vestibulo spinal tracts
What is the vestibulo-ocular reflex?
used in conjunction with the vestibulo cerebellum it coordinates eye movement with head either to keep eyes on something while head is moving, ie, head goes right, eyes go left
What must happen for eyes to move in the same direction?
inhibition on one side and stimulation on other side, the muscles would be opposite for each eye
Nystagmus
involuntary saccadic movements when the eyeball is moving or at rest.
Types of nystagmus
physiological - normal part of vestibulocular reflex( smooth eye movement away from direction of travel), or pathological - spontaneous and independent of head movements.
what causes pathological nystagmus?
damage to vestibular system componts, ie, semiciruclar canal, utricle, saccule, vestibulocerebellum
What is vestibulo-sympathetic reflex (VSR)
connects vestibular activity to posture/eyes but also to limbic so wont pass out for standing or stress
What reflex enhanses vasoconstriction to protect against fainting during stress/posture change
vestibulo sympathetic reflex VSR.
What does VSR do during nausea/seasickenss?
vasoconstriction of skin (pale) abnd sweating
Where is the vestibular cortex?
integrated inot parietal association and insular regions
What is the TPJ, temporaoparietal junction?
It has something to do with self location, first person perspctive, sense of being.
what can cause illusions or delusions from vestibular cortex?
erronerous inappropriate input from sensory system that cortex cant reconcile
Autoscopy
lack of congruence amound sensory inputs, where you can see own body separately
Dopleganger
double of living person, bad luck, illness danger or deathy
What are the three types of autoscopy?
autoscopic hallucinations, heautoscopy, out of body experience
Hutoscopic hallucinations
see douple without disembodyment
Heautoscopy
see double but uncertain of disembodied is self localized in physical or autoscopic body
Out of body
feel self center awarness outside of physical body, can see one own body or environment from elevated place.
What causes autoscopy?
disintegration of self from conflicting sensory information or vestibular and visual info
What regulates central blood flow?
vestibular system.
How does vestibular system regulate cerebral blood flow?
Increased MAP via baroreceptor and vestibular caused constriction, Increased cerebral blood from by vasodilating cerebral
IS the SNS or PNS that helps vestibular system keep cerebral blood flow adequate?
Its sympathetic inhibition to inhibit vasoconstriciton of cerebral vessels
What does vestibular nuclei do for brain blood flow regulation
to pterygopalatins ganglion to vasodilate cerebral arteries.
