Vestibular System Flashcards
Where are the auditory and vestibular receptors located?
Auditory and vestibular receptors are located in the inner ear, deep inside the temporal bone.
The ________ houses the auditory and vestibular sense organs.
bony labyrinth
The bony labyrinth consists of a series of cavities in what bone?
temporal bone
The membranous labyrinth consists of fine membranes (epithelia) that create a series of ?
interconnected sacs and ducts
The membranous labyrinth is filled with a specialized fluid called _____________
endolymph
________ lies outside the membranous labyrinth in the space between the bony and membranous labyrinths
perilymph
In each labyrinth (left and right) the auditory apparatus consists of the ______
cochlea
The vestibular apparatus consists of what two sets of sensory structures?
Three semicircular canals or ducts
and a pair of otolith organs, called the utricle and the saccule
What does the vestibular system detect?
The vestibular system detects position and motion of the head in space by integrating information from peripheral receptors located in the inner ear
The vestibular system provides the nervous system with information that is important in what two areas?
- reflex control of eye movements (the vestibulo-ocular reflex, VOR)
- reflex control of upright posture (the vestibulospinal reflex (VSR)
The semicircular canals or ducts are oriented so they can detect ____?
angular acceleration in three planes (horizontal, anterior, and posterior) and direction of head movement.
Both ends of each semicircular canal terminate in the ________
utricle
Each semicircular canal has an enlargement called the ______, where it joins the utricle.
ampulla
In one region of the ampulla, the epithelium of the canal is thickened and contains specialized receptor cells called the?
vestibular hair cells
A gelatinous mass called the _______ surrounds the hair cells
cupula
Sensory transduction is based on _______
inertia
Hair cells are stimulated only during changes in?
the rate of motion ( e.g., during acceleration of the head).
Vestibular hair cells consist of a single tall ____ and 40-70 shorter _______
kinocilium and 40-70 shorter stereocilia
Bending of the hairs towards the kinocilium causes _________
depolarization (leading to an increase in the firing rate of CN VIII)
Deflection of the hairs in the opposite direction (away from the kinocilium) causes?
hyperpolarization (and a decreasing firing rate in CN VIII).
Hair cells are arranged in each horizontal canal so that the axis of polarity (depolarization vs. hyperpolarization) points which way?
toward the center of the head
The horizontal canals lie in approximately the same plane on each side and they work together to detect?
motion.
The otolith organs provide the nervous system with what two types of information?
linear acceleration and head position with respect to gravitational forces
Hair cells are located within the utricle and saccule, supported by the _______ in each chamber
macula
Hair cells of the utricle respond most to what kind of movement?
linear acceleration and to tilting the head forward and backward
Hair cells of the saccule respond most what kind of movement?
to vertical displacements
The hairs are covered by a gelatinous substance in which tiny stones, or otoliths are embedded. Otoliths are also called otoconia. What are they composed of?
calcium carbonate
CN VIII (vestibular component) is composed of what kind of neurons?
bipolar
Superior vestibular nucleus (SVN) receives input via CN VIII from what areas?
ampullae of semicircular canals, maculae in utricle and saccule, cerebellum
Ascending axons of the super vestibular nuclei join the __________
ascending component of the MLF.
The _______ reflex is used for the coordination of head and eye movements to maintain stable gaze while the head is moving
vestibulo-ocular
The lateral vestibular nucleus (Deiter’s nucleus, LVN) receives input via?
CN VIII, primarily from the utricle
Also receives input from the vermis of the cerebellum
The lateral vestibular nucleus (Deiter’s nucleus, LVN) gives rise to what tract?
lateral vestibulospinal tract (LVST)
Which nucleus is involved in the vestibulospinal reflex which helps maintain balance and upright posture?
lateral vestibular nucleus
Medial vestibular nucleus (MVN) gets input from?
mainly from ampullae of semicircular ducts
Descending neurons in the medial vestibular nucleus give rise to the _______tract, which join the descending component of the medial longitudinal fasciculus (MLF).
medial vestibulospinal
Ascending neurons of the medial vestibular nuclei join the?
ascending component of the MLF
The Inferior Vestibular Nucleus (IVN) receives input from?
semicircular ducts, saccule, and utricle and from the vermis of the cerebellum
What is the function of the Inferior Vestibular Nucleus?
To integrate peripheral input from the vestibular apparatus with input from the cerebellum. Important for postural control.
The _______ reflex help maintain a stable visual image on the retina while the head is moving
Vestibulo-Ocular Reflex (VOR)
The rotation test is a test of _____ function
Vestibular Function
How will a normal subject react to the rotation test?
Normal subject will have horizontal nystagmus to the opposite side (i.e. to left), show dysmetria (past-pointing) and tend to fall to the same side (right), and experience a sensation of turning (vertigo) to the opposite side (left). Nystagmus lasts 15-40 seconds.
If nystagmus occurs spontaneously what is that a sign of?
It is a sign of CNS lesion affecting the vestibular system including the semicircular canals, otolith organs, vestibular pathways, and the vestibulocerebellum
What is the Caloric Irrigation Test
External auditory meatus is irrigated with either cold or warm water. Convection currents are set up in endolymph in vestibular apparatus due to temperature differential. Movement of endolymph stimulates the vestibular nerve and induces nystagmus.
How do normal subjects respond to the Calorie Irrigation Test?
cold-water irrigation results in nystagmus to the opposite side; hot water irrigation results in the reverse reactions (mnemonic COWS: cold, opposite; warm, same)
How do comatose patients respond to the Calorie Irrigation Test?
no nystagmus is seen. With brainstem intact (but still comatose), eyes deviate to the side of cold irrigation
A patient is having sensation of irregular or whirling motion; an illusion of movement when there is no movement.
What is she experiencing?
Vertigo. May result from vestibular disease or cerebellar disease.
Name the disease: Inner ear disease associated with increased production of endolymph (or decreased absorption of endolymph) and increased endolymphatic fluid pressure.
Meniere’s Syndrome (Meniere’s Disease)
Symptoms of Meniere’s Syndrome (Meniere’s Disease)?
Episodic attacks of vertigo, tinnitus (ringing in ears), hearing loss, nausea, vomiting, and sensation of fullness and pressure in the ear.
Characterized by horizontal nystagmus (fast phase to the opposite ear), past-pointing, and falling toward the affected side.
What is Labyrinthitis?
Inflammation of labyrinth possibly due to bacterial or viral infections or to toxicity (e.g., due to alcohol, quinine, salicylates)
What are the symptoms of Labyrinthitis?
Symptoms are same as Meniere’s disease: vertigo, tinnitus, hearing loss, nausea, vomiting, sensation of fullness and pressure in ear. Characterized by horizontal nystagmus (fast phase to the opposite ear), past-pointing, and falling toward the affected side.
___________ is the most common cause of recurrent vertigo; elicited by certain head positions.
Benign Paroxysmal Positional Vertigo (BPPV or BPV)
True/False Benign Paroxysmal Positional Vertigo (BPPV or BPV) is associated with tinnitus or hearing loss.
False
What is cupulolithiasis?
A. Dislodging and dislocation of the utricular macular otoliths to the cupula of the posterior semicircular duct
B. Adherence of the otoliths or otoconia to the cupula
What is canalithiasis?
Canaliths (i.e., the otoliths that have fallen into the semicircular canals) free-float in the semicircular canal, causing abnormal movements of the endolymph
Common cause is a conflict in sensory input from visual and vestibular receptors may cause?
Motion sickness
What are the signs of motion sickness?
Signs of motion sickness include:
- visual and postural instability
- pallor
- diaphoresis
- excessive salivation
- headaches
- anxiety
- nausea
- vomiting
Habituation training is used to help diminish motion sickness. How does it work?
repetitive vestibular and visual stimuli are presented. The abnormal responses to the provocative stimuli are gradually diminished, and the patient experiences less motion sickness.
__________ is a hallmark of neurofibromatosis 2 (NF2), is an autosomal dominant disease characterized by formation of multiple tumors in the central and peripheral nervous system.
Vestibular Schwannoma (Acoustic Neuroma)
Vestibular Schwannoma (Acoustic Neuroma) symptoms?
Vestibular and/or cochlear (CN VIII) dysfunction (vertigo, dizziness, tinnitus, hearing loss, facial weakness, loss of corneal reflex due to CN VII involvement).
________ is a vestibular dysfunction (vertigo and imbalance) may also occur after implantation of cochlear prosthesis to improve hearing.
Cochlear Prosthesis
