First you tell them what your gonna tell The vestibular system them
Michael E. Goldberg, M.D. • The vestibular organs sense head motion: canals sense rotation; otoliths sense linear acceleration (including gravity). • The central vestibular system distributes this signal to oculomotor, head movement, and postural systems for gaze, Please sit where you can examine a partner head, and limb stabilization.. • The visual system complements the vestibular system. • Visuo-vestibular conflict causes acute discomfort. • Peripheral and brainstem vestibular dysfunction causes pathological sense of self-motion and visuo-vestibular conflict.
The vestibular labyrinth answers two The vestibular labyrinth answers the two questions basic to the human condition by questions basic to the human condition sensing • Where am I going? • Head angular acceleration (semicircular canals) •Which way is up? • Head rotation. • Head linear acceleration (saccule and utricle) • Translational motion. • Gravity (and by extension head tilt).
The vestibular organ lies in the temporal The vestibular organ bone
Vestibular Nerve Anterior vertical canal
Facial Nerve Horizontal canal Vestibulocochlear (VIII) Nerve Foramen Magnum Cochlear Nerve Posterior vertical canal Cochlea Saccule Utricle
1 Each vestibular organ has a sensor for head Deformation of the stereocilia towards acceleration, driven by hair cells similar to those in the cochlea the kinocilium causes hyperpolarization
• In the cochlea vibration induced by sound deforms the hair cells. • In the labyrinth acceleration deforms the hair ⇒ depolarization cells. ⇐ hyperpolarization • In the semicircular canals the sensing organ is the ampulla
How the semicircular canals sense Hair cells respond to deformation rotation
Hair Cell Cupula Ampullary Crista Ampulla
Semicircular Endolymph Canal
Vestibular Neuron
The three semicircular canals lie in 3 The semicircular canals are functionally orthogonal planes paired and sense rotation
Cochlea • Horizontal canals: rotation in the horizontal Cochlear N Anterior plane Vertical Vestibular N • Left anterior and right posterior canals (LARP): Canal rotation in the vertical plane skewed 45° Horizontal Vestibulo- anteriorly to the left. Canal Cochlear N • Right anterior and left posterior canals (RALP): (Nerve VIII) rotation in the vertical plane skewed 45° Posterior Vertical anteriorly to the right. Canal
2 The semicircular canals are functionally The otolith organs sense linear paired acceleration. Hair cells lie in the macula.
Otoconia Otolithic • The canals lie in roughly the membrane
same planes as the extraocular muscles: Striola Otoconia (ear dust) •Horizontal canals: lateral and
medial recti. Otolithic •LARP: left vertical recti, right Membraine obliques.
•RALP: right vertical recti, left obliques.