52 Auditory and vestibular pathways Flashcards
The oval window is covered with ________ (bone) and they are linked by ________.
Stapes;
ligaments
The round window is covered with _________________, a layer of fibrous tissue between epithelium on either side.
Secondary tympanic membrane
What is the bony and the membranous labyrinth?
The hard bone of the cochlear;
membranous = contains the endolymph
Describe the route of drainage of the endolymph.
Aqueduct of vestibule contains the endolymphatic duct > sac > drains the endolymph into the dural venous sinuses.
Describe the route of drainage of the perilymph.
Perilymph exits to the subarachnoid space by the perilymphatic duct/ cochlear aqueduct.
What are the difference between the bony labyrinth and the membranous labyrinth in vestibular functions?
Bony VS membranous:
- semicircular canals VS semicircular ducts
- vestibule - aqueduct of vestibule VS utricle and saccule - endolymphatic duct and sac
What are the difference between the bony labyrinth and the membranous labyrinth in auditory functions?
Bony VS membranous:
Cochlea VS cochlear duct
What are the sensory epithelium (hair
cells + supporting cells) in the parts of
- Ampulla of semicircular duct?
- Utricle and saccule?
- Cochlear duct?
- Crista ampullaris
- Macula
- Spiral organ
The cochlea is a __________-filled tube which wraps around itself approximately ____ times.
perilymph;
2.5
In 3 different parts, the hairs (kinocilia and sterocilia) of sensory cell project into the
overlying gelatinous mass:
Cupula, otolith membrane, tectorial membrane
The bony cochlea turns around a central bony _____________, which forms the axis of the cochlear
turns.
modiolus
The spiral lamina is a ridge of bone that divides the cochlear cavity into two chambers:
the ___________ and the _____________.
scala vestibule;
scala tympani
The ____________ is suspended in the
endolymph within the scala media. It rests on the __________ membrane as its spirals within the cochlear turns.
organ of Corti;
basilar
What is spiral ligament? Function?
- thickened endosteum (fibrous cushion between stria vascularis and bony otic capsule)
- gives perilymph
____________ is a portion of the spiral ligament that is vascularised and secretes _____________.
Straie vascularis;
endolymph
The apical regions of the supporting and pillar cells of organ of Corti are tightly joined together to form the ______________ which is permeable/impermeable.
Reticular lamina;
impermeable
How can the brain control the sensitivity of hair cells?
Cortex > superior colliculus > CN8 > outer hair cells > beat to control apposition of the tectorial membrane
In scala vestibuli and tympani, what is the relative ionic concentrations of Na+ and K+?
[Na+] > [K+] in perilymph
The auditory pathway is bilateral but predominantly ____________.
Contralateral
Cochlear nucleus:
Dorsal nu: contralateral;
Ventral nu: bilateral
State the flow of the main auditory pathway.
Superior olivary nucleus >
Lateral lemniscus >
Inferior colliculus >
Medial geniculate nucleus
What is the trapezoid body?
From ventral cochlear nucleus, collection fibers on ventral aspect passing through the SON and the medial lemniscus (to contralateral side)
State the 4 functions of SON.
- Sound localization
(different arrival time and intensity between ears) - Modulation of sensitivity: SON > outer hair cells
- Acoustic reflex for dampening sound : SON > CN7 > stapedius m.(CN7) + tensor tympani (motor V)
- Attention (Tectospinal tract):
auditory signals > reticular formation, superior colliculus > neck muscles
Semicircular canal contains _________________ at the ampulla that detects angular acceleration.
Crista (ampullaris)
Utricle and saccule are the ____________ that contains _________ which are at right angle to each other.
otolith organs;
macula
Macula of utricle: horizontal plane;
Macula of saccule: vertical plane
Vestibular ganglion at the internal acoustic meatus:
Vestibular nerve runs between the _____________ and ____________, and project to superior, medial, inferior vestibular nuclei.
(Lateral vestibular nuclei: balance, receives proprioception directly from muscles)
spinal trigeminal tract and the inferior cerebellar peduncle
List 4 vestibular connections.
1. Spinal cord (vestibulospinal reflex, vestibulocervical reflex) 2. Eye (VOR) 3. Cerebellum 4. Cerebral cortex
In vestibulospinal reflex, which vestibular nucleus is involved, what is the target, functions and laterality?
Lateral vestibular nucleus;
Target: whole spinal cord via the lateral vestibulospinal tract;
Functions: modulate tone of axial limb extensor muscles, feedback from muscles for regulation of muscle tone;
Ipsilateral
In vestibulocervical reflex, which vestibular nucleus is involved, what is the target, functions and laterality?
Medial vestibular nucleus;
Target: mainly cervical via medial vestibulospinal tract (in descending MLF);
Functions: stabilize head in space by activating neck muscle;
Bilateral
Which vestibular nuclei/nucleus is/are involved in VOR?
Superior and medial vestibular nuclei
VOR excites the _________(laterality) ___________(nucleus) and inhibites the _________(laterality) ___________(nucleus).
contralateral CN6
and ipsilateral CN3
are excited
ipsilateral CN6 inhibited
CN8 and superior vestibular nucleus projects to _____________ of the cerebellum _________(laterality) . They in turn project to _______ vestibular nuclei __________ (laterality).
Flocculonodular lobe and vermis; ipsilaterally;
all 4; bilaterally
In tracking eye movement, VOR is suppressed via ____________ to vestibular nucleus. What is the pathway involved?
cerebellum connection;
Retina > cortex > superior colliculus > pontine nucleus > cerebellum > vestibular nucleus
List the vestibular areas in the cortex.
- Anterior cingulum (from VP nucleus of thalamus)
- Inferior parietal lobule
- Parietal-temporal-insular region
- Near face area of somatosensory area
What are functions of vestibular connections with cerebral cortex?
- coordinate movement
- conscious sense of motion, spatial orientation, head position
