hearing and balance Flashcards
inner ear
- vestibule of the ear
- semicircular canals
- cochlea
cochlea
auditory portion of the ear
organ of hearing
organ of corti
membranes separating perilymph fluid
- vestibular membrane
- tympanic membrane
hearing process
- hair cells vibrate
- signals sent to auditory neurons via neurotransmitters
- forms the cochlear portion of CNVIII
- info to CNS
auditory pathway
direction of sound auditory pathway
quality of sound auditory pathway
primary auditory cortex a1
- superior temporal gyrus, close to the lateral fissure
- topographical map of the cochlea
- low frequency anterior area of a1 (apex of cochlea)
- high frequency posterior area of a1 (base of cochlea)
secondary auditory cortex a2
- posterior to a1
- on the superior temporal gyrus, includes Wernicke’s area
- analyzes acoustic stimuli at a higher neuronal level (recognition and interpretation of sounds on the basis of past experience)
ablation of the auditory cortex result
inability to distinguish the temporal order of sound
ablation
surgical removal
types of hearing loss
- conductive hearing loss
- sensorineural hearing loss
conductive hearing loss
- problems in the external ear (blockage) or middle ear (otitis, glue ear, damaged ossicles)
- caused by fluid, allergies, foreign objects, ruptured eardrum, impacted ear wax
sensorineural hearing loss
- malfunction of the inner ear (cochlea)
- at the level of hair cells or the auditory nerve
- rarely caused by damage to auditory brain
- caused by again, toxicity, loud noise, blast/explosion, tumors
vestibular apparatus
- balance
- spatial orientation
3 sources of sensory information in equilibrium maintenance
- eyes
- propioception
- vestibular system
components that deal with chaotic movement information
- static labyrinth
- kinetic labyrinth
static labyrinth
- linear acceleration and spatial orientation
- otolith organs
kinetic labyrinth
- angular acceleration
- semi-circular canals on 3 planes that make 90 degree angles with each other
- cupula covers crista ampullaris on the ampulla
- movements of endolymph stimulate bending of cupula
- movement of cupula stimulates movement of hair cells
- movement of hair cells detect head movements
otolith organs
- 2 endolymph containing chambers
- utricle and saccule (vestibule)
- contain macula that respond to endolymph movements
macula
- clusters of hair cells
- detect linear movements and proprioception of the head
utricle
- posterior part of the vestibule
- communicates with semi-circular canals on one end and saccule on the other
- detect movements in the horizontal plane
saccule
- anterior part of the vestibule
- smaller than utricle
- joins the utricle and communicates with the cochlea
- detect movements in the vertical plane
semi-circular canals
- membranous channels filled with endolymph
- located on 3 planes, make 90 degree angles with each other
ampulla
terminal part of each semicircular canals
crista ampullaris
a cluster of hair cells on each ampulla
cupula
gelatinous structure covering crista ampularis
vestibular pathway (elongated)
- vestibular nerve input from crista ampullares, semicircular canals, utricle, saccule
- info to superior vestibular nucleus of bechtrew, medial vestibular nucleus of schwalbe, inferior vestibular nucleus of roller, lateral vestibular nucleus of dieters
pathways that project from vestibular nuclei to the cerebellum function
joint modulation of balance by the cerebellum and vestibular system
vestibular pathway (simplified)
illnesses of balance
- peripheral vertigo
- benign paroxysmal positional vertigo (bppv)
- central vertigo
peripheral vertigo
- symptoms are a result of inflammation
- labyrinthitis
- vestibular neuritis
- menieres disease
- caused by high pressure of endolymph
labyrinthitis
inflammation of the inner ear labyrinth and vestibular nerve
vestibular neuritis
inflammation of vestibular nerve
menieres disease
due to bacterial and viral infections, metabolic disorders, autoimmune disease
benign paroxysmal positional vertigo
- most common cause of vertigo
- small crystals break free and float around freely within the semi-circular canals
- disturbance of the otolith particles
central vertigo
- affects the pathways of the vestibular system
- very rare
- most common symptom is accompanying migraine
