lecture 26 - vestibular physiology Flashcards
What are the 2 functions of the vestibular system?
Balance, equilibrium (maintaining orientation/position)
What are the key structures of the vestibular system?
semi-circular canals, otolith organs, membranous labyrinth, hair cells
What are the functions of the semi-circular canals?
Sense rotational acceleration, and detect start/stopping movement
What are the 3 semi-circular canals?
Horizontal, anterior, posterior
What is the crista ampullaris?
The functional unit of the semi-circular cells that contains the stereocilia which detect movement
What is the function of the cupula in the crista ampullaris?
Is a gelatinous structure that contains the hair cells. Movement of fluid in the semicircular canals distorts the cupula and therefore bends hair cells
How do vestibular hair cells generate a nerve signal?
As sterocilia on hair cells are moved towards the kinocilium by pressure from moving fluid, they causing membrane distortion which generates an action potential.
What is the term for the fluid found in the semicircular canals?
Endolymph
What is the property of endolymph that allows the vestibular system to detect rotation?
Endolymph has greater intertia than bone, so it moves at a different speed to the skull. Therefore, it pushes on the cupula, which is fixed in the skull, bending hair cells
Which nerve is associated with the vestibular system?
The vestibulocochlear nerve (CN IX)
What are the 2 otolith organs?
Saccule, utricle
What is the function of the otolith organs?
They detect falling/gravitational field
How do the otolith organs detect falling?
They contain otoliths, which are heavy structures that move with gravity, triggering hair cells
What is the vestibulo-ocular reflex?
A connection between the vestibular system and the ocular muscles that moves the eyeballs to maintain fixation during movements
What is physiological (normal) nystagmus?
A process of alternating back-and-forth eye movements that allow fixation on objects while moving past
