11 - Vestibular System: Peripheral Receptors and Central Pathways Flashcards
What is the function of the vestibular apparatus?
Maintain upright posture, adjust head position in response to changes in posture, coordinate eye movements with each other, and coordinate eye movements to compensate for head movements.
What is linear acceleration? What is angular acceleration?
Linear: head movement along a single place
Angular: head rotation in a single plane or simultaneous change in velocity and direction
What does the bony labyrinth contain?
Semicircular canals, cochlea, and the vestibule of the inner ear.
Describe the anatomy of the vestibular apparatus?
Bony labyrinth with membranous labyrinth inside.
Between the bony labyrinth and the membranous portion is perilymph. Inside the membranous labyrinth is endolymph.
Sensory receptors are in the macula of the utricle, in the macula of the saccule, and the semicircular canals with crista ampullaris.
The maculae in the utricle and saccule detect what? How do they do this?
Linear acceleration.
Specialized spots of epithelium that contain sensory hair cells (mechanoreceptors) called maculae.
Hair cells project into the otolythic membrane (gelatinous) and when the membrane moves the cilia deflect towards the true cilium called the kinocilium resulting in depolarization of the cell.
What is the appearance of a macula hair cell?
They have bundles of surface projections called stereocilia arranged in rows that abut a taller kinocilium.
These are all covered by the gelatinous otolythic membrane.
The macula in the utricule lies in the _____ plane, while the macula in the saccule lies in the ______ plane.
Utricle: horizontal
Saccule: vertical
What are the sterocilia and kinocilium bundles polarized towards? What type of movements is this involved in?
A ridge that cuts across the macula.
Deflection towards kinocilium results in polarization while deflection away from kinocilium results in hyperpolarization.
Involved in front to back and side to side movements (lineear acceleration).
What are tip links? What is their function?
Proteins on the top of stereocilia that link them to kinocilium.
When inclined in one direction, the tip link is pilled like a slinky, which causes it to open ion channels, resulting in depolarization of hair cells.
A pattern of differential hair cell signaling across the maculae is transmitted to the brainstem via _____. What is this process called?
CN 8.
This pattern of cells firing gives information to the brain and is called called population coding.
What are ampullae? What does each contain?
Enlarged ends of the semicircular canals (single is ampulla).
Each ampulla contains a ridge of sensory epithelium called the crista ampullaris.
If you cross-sectioned an ampulla, what are the regions that you would see? What happens in this region during movement?
Top surface ridge of sensory epithelium called crista ampullaris embedded in a gelatinous material called the cupula.
The epithelium is composed of hair cells that have stereocilia and movement of fluid in the canal (endolymph) causes a wave in which the whole ridge will be pushed by the cupula which acts as a sail.
The _______ is the location of sensory epithelium that’s covered by gelatinous material called _____.
Crista ampullaris
The cupola
What is the physiology of the vestibular apparatus? How does endolymph move in response to movement?
Rotation of the heads means rotation of the bony labyrinth, which sets up movement of the endolymph within the membranous labyrinth.
Endolymph moves in opposite direction of head turn and delfects cupula and stereocilia towards the kinocilium which causes depol of hair cells.
This sends signals through the vestibulocochlear nerve to get info about movement to the brain.
Semicircular canal detects ______ in speed of head rotation.
CHANGES.
