Hearing and Balance Flashcards
inner ear components
- membranous labyrinth
- bony labyrinth
three main parts of inner ear
- vestibule of ear
- semi-circular canals
- cochlea
modiolus
centre of the curved part of the cochlea
where is the organ of corti located
within cochlear duct
where is perilymph located
within vestibular and tympanic canals
another name for the vestibular canal
scala vestibuli
another name for the tympanic canal
scala tympani
vestibular canal components
oval window and vestibular membrane
tympanic canal components
round window and basilar membrane
what two ducts act as one
cochlear and vestibular
what is the cochlear duct filled with
endolymph
two nerves in the vestibulo cochlear nerve
vestibular nerve and cochlear nerve
vestibular nerve function
balance
cochlear nerve function
hearing
simple auditory pathway
Cochlear nerve → cochlear nuclei→ inferior colliculus → thalamus → primary auditory cortex
where are the cochlear nuclei located
pons
where is the inferior colliculus located
midbrain
name the two cochlear nuclei
- dorsal
- ventral
do both cochlear nuclei decussate
yes
ventral nucleus pathway function
direction of sound
ventral nucleus pathway
Cochlear nerve → ventral CN → superior olivary nucleus→ nucleus of lateral lemniscus → inferior colliculus → medial geniculate nucleus of thalamus → (auditory radiations) → primary auditory cortex
where is the superior olivary nucleus founf
mid pons
what is the dorsal nucleus pathway responsible for
quality of sound
dorsal nucleus pathway
Cochlear nerve → dorsal CN → (dorsal acoustic stria) → inferior colliculus → medial geniculate nucleus of thalamus → primary auditory cortex
where is the primary auditory cortex (A1) located
superior temporal gyrus, close to lateral fissure
what part of A1 relates to low frequencies
- anterior part
- corresponds to apex of cochlea
what part of A1 relates to high frequency sounds
- posterior part
- corresponds to base of cochlea
where is the secondary auditory cortex (A2) found
posterior to A1 on superior temporal gyrus
what is included in A2
wernickes area
A2 function
analyses acoustic stimuli at a higher neuronal level (recognition and interpretation of sounds on the basis of past experience)
results of ablation of A2
inability to distinguish temporal order of sound
conductive hearing loss causes
- problems in outer ear (blocked by wax)
- problems in middle ear (otitis, glue ear, damaged ossicles)
sensorineural hearing loss causes
- malfunction of inner ear (cochlea)
- generally at level of hair cells or auditory nerve
- rarely by damage to auditory brain
two functions of vestibular apparatus
- sense of balance
- spatial orientation
three sources of sensory information used to maintain equilibrium
- eyes
- proprioception
- vestibular system
two components that deal with chaotic movements
- static labyrinth
- kinetic labyrinth
static labryinth functions
linear acceleration and spatial orientation
what is contained in otolith organs
endolymph and macula (hair cells)
two otolinth organs
- utricle
- saccule
what does the utricle contain
macula utriculi
what does the saccule contain
macula saculi
what do the macula detect
- linear movements of the head
- proprioception of the head
where is the utricle
posterior part of vestibule
what does the utricle communicate with
semi-circular canals on one end and saccule on the other
utricle function
detects movements on the horizontal plane
where is the saccule
anterior part of vestibule
what does the saccule communicate with
utricle and the cochlea
saccule function
detects movements in the vertical plane
which is smaller, utricle or saccule
saccule
kinetic labyrinth function
angular acceleration
how many semi-circular canals are there
3
what are the semicircular canals
membranous channels filled with endolymph
where are the semicircular canals located
on three planes which make 90 degree angles with eachother
what are the three planes of the smeicircular canals
- lateral
- posterior
- anterior
what is the ampulla
- terminal part of semicircular canal
- open to utricle
- has crista ampullaris covered with gelatinous structure called the cupula
what is the crista ampullaris
cluster of hair cells
how are head movements detected in the kinetic labyrinth
- movement of endolymph stimulates the bending of the cupula
- movement of the cupula stimulates the movement of the hair cells
- movement of the hair cells detect head movements
superior canal function
detects nodding
lateral canal function
detects head shaking (no)
posterior canal function
detects head tilt
where can inputs come from in the vestibular pathway
- cristae ampullares
- rest of semicircular canals
- utricle
- saccule
name the four vestibular nuclei
- superior vestibular nucleus of bechterew
- medial vestibular nucleus of schwalbe
- inferior vestibular nucleus of roller
- lateral vestibular nucleus of dieters
medial longitudinal fasciulus
superior/medial vestibular nuclei → motor neurons of occulomotor, trochlear and abducens nerves
function of medial longitudinal fasciculus
mediates reflexive activities of extra-occular muscles
inferior vestibulospinal tract
inferior vestibular nucleus → interneurons in cervical spinal cord
function of inferior vestibulospinal tract
adjusts tone and posture of head and neck muscles
lateral vestibulospinal tract
lateral vestibular nucleus → interneurons in entire spinal cord
function of lateral vestibulospinal tract
adjusts tone and posture of muscles
main vestibular pathway
Vestibular nerve → vestibular nuclei → ventral posterior nuclei of thalamus → primary vestibular cortex → primary motor cortex
what happens in the primary vestibular cortex
information from vestibular system is integrated with other proprioceptive systems
what happens in the primary motor cortex
vestibular pathway
motor response to information from vestibular and other proprioceptive systems is generated
name three types of vertigo
- peripheral vertigo
- benign paroxysmal positional vertigo
- central vertigo
peripheral vertigo
- symptoms occur as a result of inflammation
- this form of vertigo is thought to be caused by high pressure of endolymph fluid
three types of inflammation which cause peripheral vertigo
- labyrinthitis - inflammation of inner ear labyrinth and vestibular nerve
- vestibular neuronitis - inflammation of vestibular nerve
- meniere’s disease - due to bacterial and viral infections as well as metabolic disorders and autoimmune diseases
BBPV cause
small crystals break free and float around freely within semi-circular canals (disturbance of otolith particles)
central vertigo
- affects pathways of vestibular system
- most common symptoms is accompanying migraine
most common type of vertigo
BBPV
rarest type of vertigo
central vertigo
