part 3 Flashcards
location and shape of utricle
horizontal and closer to semi-circular canals
location and shape of saccule
vertical and closer to cochlea
what does saccule do?
linear acceleration; gravity
what is macula
surface that contains haircells
- its flat and not cristae anymore
what is otoconia
calcium carbonate crystals
what is striola
central region of macula
otolithic membrane’s specific gravity
is higher than that of endolymph because of the otoconias in the otolith organs (stones added to gel so it is heavier)
kinocilia of utricle
towards striola
kinocilia of saccule
away from striola
utricle
horizontal linear acceleration and static head tilt
- encodes linear accelerations (not angular)
saccule
vertical linear acceleration
encodes jumping up and down, going on elevator
otolith organs encode
linear acceleration and static tilt
anterior posterior acceleration and lateral acceleration encoded by
utricle (b/c in horizontal plane)
occipital-caudual accelerations encoded by
saccule because in vertical plane
what are occipital-caudual accelerations
roll
yaw- shake head no
pitch- shake head yes
static upright tilt encoded by
saccule
static pitch and roll encoded by
utricle
what is not encoded by otolithic organs
static yaw (both motion and static position)
forward acceleration
sterocillia move toward kinocilium increase firing rate
car in reverse (backward acceleration)
sterocilium move away from kinocilium and decrease firing rate
head upright (upright tilt)
resting firing rate
head tilted forward (looking down)
otoconia move down bending sterocilium away from kinocilium decreasing firing rate;
- utricle encode static tilt, SCC encode motion
Blood supply from otolithic organs comes from where
Basilar artery or Anterior inferior cerebellar artery (AICA)
anterior vestibular artery
from internal auditory artery (labryrinthine artery) utricle, AC (anterior SCC) and HC (horizontal SCC)
posterior vascular artery
from common cochlear artery
- saccule, PC
1st neuron
scarpa ganglion
- internal auditory ear canal, close to pontocrebellar angle; axons bundled together in 15-20K a vestibular nerve fibers leading to the vestibulo-cochlear nerve
2 branches of the vestibulo-cochlear nerve
superior vestibular- Utricle, AC, HC
inferior vestibular- Saccule, pc
2nd neuron
innervation- vestibular nuclear complex.
vestibular nerve bifrucates at pontomedullary junction into 1. primary superior vestibular afferents and 2. primary inferior vestibular afferents
commisural fibers
L & R vestibular nuclear complexes connected with these fibers through which information is projected contralaterally
vestibular pathway 3rd neuron
vestibular end organs send info that travels to the vestibular nuclei in the brainstem
what are the main projections of the vestibular nuclei to
spinal cord (controls head and body postion)
3 extraocular motor nuclei (III IV VI, control eye movement VOR)
Cerebellum (coordinates postural adjustments)
Thalamus (eventually reaching cortex & Conscious perception of movement and gravity) and the emetic pathway (causing vomiting
