Anatomy
The base of the hair cells is bathed in ____________ (high concentration of Na+ and similar to CSF)
Perilymph
The apex of the hair cells is bathed in endolymph fluid (high concentration of K+)
The longest stereocilia, they can bend towards or away from this
Kinocilium
In the ampulla, the movement of the this fluid due to angular rotation deflects the stereocilia
endolymph
The structures that make up the labyrinth
3 Semicircular canals
2 otolith organs
The swelling (bulbs) at each end of the semicircular canals that sense rotational acceleration
Ampulla
Crista's ampullaris is surrounded by this membrane
Cupula
The stereocilia extend out from the crista into the gelatinous bulb called the cupula which is as tall as the ampulla
Which canal?
“Pitch”
Example: the nodding gesture, moving your head up and down
Superior (anterior) Canal
This type of acceleration is when force is applied to an object that moves in a line, like stopping in a car or falling down
Linear
These sense linear acceleration & position relative to gravity
Saccule & Utricle
Hair cells in the vestibular system __________ when their stereocilia are deflected towards to the kinocilium.
Depolarize
Which canal?
“Yaw”
Example: the gesture of shaking your head left to right
Horizontal Canal
The macula of the utricle and the macula of the sacculus is surrounded by this membrane
Otolithic Membrane
To help detect changes in linear acceleration, the fluid in your vestibular system has “ear stones” called this which experience inertia (like your body does in the car).
Otoconia
A backwards head tilt, equivalent to forward acceleration causes ___________
Depolarization
In this situation backwards head tilt and forward acceleration leads to hair cells sending the same signal!
Which canal?
“Roll”
Example: the gesture of tilting your head left to right
Posterior Canal
The axons of the vestibulocochlear nerve project to this region, which are found in the brainstem ear the junction between the pons and medulla
Vestibular nuclei
The hair cells are embedded in the ampulla’s sensory epithelium called this.
Crista
Hair cells in the ____________ are all orientated in the same direction, while hair cells in the saccule and utricle have opposing orientations
ampullae
When we turn our head to the right, vestibular fibers innervating hair cells in which (L or R) horizontal canal will show increased firing?
Right
Key Point: Depolarization occurs on the side being turned to
This medication works to inhibit input into the vestibular nuclei and “vomiting center”
Anticholinergics like Scopolamine can be used as a prophylactic to motion sickness