Vestibular system - Rennie Flashcards
Recognize and name the components of the vestibular system.
Describe the hair cell and its physiology.
Explain how the vestibular sensors communicate motion information.
Discuss the three vestibular motor reflexes.
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What are the otolith organs? What does each do?
Saccule - Fibers project horizontally (elevator)
Utricle - Fibers project vertically, senses tilt of the head from vertical (respect to gravity)
Both detect linear acceleration. They detect postural changes, and are referred to as “static” receptors.
The hair cells of these two organs are perpendicular to one another.
Where are the vestibular system and the cochlea honused?
In the petrous portion of the temporal bone.
What are the organs of the vestibular system? Which detect angular motion?
3 semicircle canal organs and their ampullae (angular motion) Otolith organs (Saccule and Utricle)
Each side of the head has a horizontal, anterior, and posterior canal. When paired with the contralateral side, which work together?
Horizontal both work together.
Anterior work with the contralateral posterior because they lie in the same plane.
From the end vestibular organs, where do neurons project?
The vestibular afferent nerves (VIII) have cell bodies in Scarpa’s ganglion and project to the ipsilateral vestibular nuclei located at the border of the caudal pons and rostral medulla.
[The vestibular nuclei integrate vestibular signals with information from the spinal cord, cerebellum and visual system.]
There are four vestibular nuclei. What are their names?
Superior
Medial
Lateral (Dieters)
Descending (Inferior)
To which nuclei do the canals project? What movement is largely controlled by this system?
Superior and medial
Mediated gaze control.
To which nuclei do the utricles project?
Lateral, Descending, and Medial
How do the semicircular canals sense movement?
The ampulla of each contains “hair cell” which function like the hair cells in the cochlea. Movement of endolymph across the hair cells causes either depolarization or hyperpolarization.
Endolymph lags behind movement of the head, so will move in the opposite direction. So, turning the head to the left will cause a rightward movement of endolymph. This will depolarize the left horizontal and hyperpolarize the right.
Endolymph concentrations of K, Ca, Na (relative)?
High K
Low Ca
Low Na
Does the vestibular nerve fire at rest?
Yes
What inputs does the lateral nucleus receive? What does it mediate?
Canals and otoliths. Postural reflexes.
What system leads to Nystagmus?
The Vestibular Ocular Reflex allows stable eye tracking during head motion.
