Vestibular System (Exam 2) Flashcards
2nd most common health complaint in the US.
Dizziness
Leading cause of falls for elderly.
Dizziness
_____ related falls account for greater than one-half of accidental deaths in the elderly.
Balance
Describe everything from feeling faint, weak, unsteady, experiencing blurred vision, or vertigo.
Dizziness
Feelings of dizziness may stem from?
Medication side effects. Head or neck injuries. Brain disorders. Body’s sensory information. Vestibular system.
Information about the body position relative to the environment. Depth, velocity, and motion perception.
Visual System
Information about movement of body parts in relation to other body parts. Information about pressure changes from ground.
Somatosensory System (Proprioception)
Inner ear mechanism monitoring head position.
Vestibular System
3 Primary Functions of Vestibular System
Stabilize vision during head movement. Maintain postural stability. Provide information for spatial orientation.
4 paired nuclei. Destination of vestibular primary afferents. Primary processor of vestibular input. Implements direct, fast connections between incoming vestibular information and outgoing motor response.
Vestibular Nuclear Complex
“Real Time” Processor. Monitors vestibular performance and adjusts central processing. Major recipient of information from vestibular nuclear complex. Processes visual, somatosensory, and vestibular sensory information.
Cerebellum
Houses vestibular apparatus.
Labyrinth
Sense rotation motion.
Semicircular Canals
Sense linear acceleration.
Otolith Organs
Communicate vestibular information to vestibular nuclei.
Eighth Cranial Nerve.
Named for complexity of convoluted shape. Located deep within the temporal bone. Continuous with cochlea. Uses specialized sensory (hair) cells to transduce physical motion into neural impulses. Houses the vestibular apparatus.
Labyrinth
Sense rotation. 3 canals in each ear. Perpendicular. Functionally paired canals.
Semicircular Canals (SCC)
3 Canals In Each Ear.
Anterior, Horizontal, Posterior
Left Anterior
Right Posterior
Left Posterior
Right Anterior
Left Horizontal
Right Horizontal
Enlargement at base of each SCC. Contains cupula.
Ampulla
Gelatinous barrier containing hair cells.
Cupula
Kinocilia
Larger
Stereocilia
Smaller
Sensory organ of rotation. Hair cells rest on crista ampullaris.
Crista Ampullaris
Slightly more dense than water. Travels feely around SCCs in response to head motion.
Endolymph
Stereocilia deflect toward kinocilia.
Excitation
Stereocilia deflect away from kinocilia.
Inhibition
Stimulation of CNVII results in _____.
Eye movement.
Deflection of the stereocilia caused by motion of the endolymph results in stimulation of _____.
CNVIII (Cranial Nerve 8)
Sense linear acceleration. Are sac like structures. Contain macula (sensory receptor).
Otoliths
2 Otolith Organs
Utricle, Saccule
Horizontal linear acceleration.
Utricle
Vertical linear acceleration.
Saccule
Located in each otolith organ. Consists of hair projecting from hair cells. Hairs in gelatinous membrane. Hairs are topped with otoconia (crystals).
Macula
Changing head position tilt the ____. Weight of otoconia displaces gelatin. Displaced gelatin bends hairs. Bending hairs signal vestibular nerve.
Macula
Sensory nerve arising from the brainstem. Splits into 2 portions (cochlear, vestibular) upon entering inner ear.
Vestibulocochlear Nerve
Carries information about hearing.
Cochlear Nerve
Carries information about balance.
Vestibular Nerve.
Transmits sound and equilibrium information from the inner ear to the brain.
CNVIII
Symptoms of CNVIII Damage
Hearing loss. Ringing of the ears. Nausea. Severe dizziness. Difficulty maintaining balance.
Reduces the appropriate neural output for spatial orientation, postural control, and eye movement control. (Peripheral or Central Origin)
Vestibular Dysfunction
Individuals with Vestibular Dysfunction Symptoms
Faitness, lightheadedness, imbalance, falls, nausea, vomiting, blurred vision, vertigo. Symptoms typical increase with body movements.
Involves the vestibular nuclear complex and the cerebellum, as well as structures of the reticular activation system, midbrain, and higher centers of cortical function.
Central Pathology
Affects integration and processing of sensory input. Head trauma, brainstem strokes, MS, cerebellar degeneration.
Central Pathology
Involves the inner ear vestibular structures as well as the vestibular portion of the CNVIII.
Peripheral Pathology
Diminishes available sensory information regarding head position and movement. Vestibular neuritis, labyrinthitis, meniere’s disease, BPPV, vestibular hypo function, labyrinthectomy.
Peripheral Pathology
Direction of Nystagmus
Changing (Central)
Fixed (Peripheral)
Provoked by Motion
No (Central)
Yes (Peripheral)
Effect of Visual Fixation
Increased (Central)
Decreased (Peripheral)
Visual Pursuit
Abnormal (Central)
Normal (Peripheral)
VOR (Vestibular Occular Reflex) Cancellation
Abnormal (Central)
Normal (Peripheral)
Generally caused by a virus. Acute onset lasting 2-3 days.
Inflammation of Vestibular Nerve. Vestibular Neuritis.
Associated with inner ear infection. Acute onset lasting 1-4 days.
Inflammation of Labyrinth
Associated with abnormal inner ear fluid pressure. Etiology unknown.
Meinere’s Disease
Non-malignant. Sudden onset. Provoked by head motion. Intense rotation sensation. Associated with otoconia displacement. Vertigo lasting less than 2 minutes.
Benign Paroxysmal Positional Vertigo (BPPV)
Falling toward impairment. Affected side is not functioning at normal levels. Causes imbalance of information. Unilaterally or Bilaterally. Bilateral loss eliminates internal sense of gravity. Associated with infection.
Vestibular Hypofunction
Destroys the entire labyrinth.
Labyrinthectomy
Slowing growing tumor on the CNVIII. Not cancerous.
Acoustic Neuroma
Quick, simultaneous movements of both eyes in the same direction that serve as a mechanism for fixation.
Saccades
Simultaneous movement of both eyes in opposite directions to maintain binocular vision.
Vergence
One eye one way and other eye the other way.
Divergence
Rapid, rhythmic, involuntary coupled movement of the eyes. Side-side, up-down, circular.
Nystagmus
