Vestibular System
Stimulus
Linear acceleration
Rotational Acceleration
Forwards and backwards
Laterally
Up and down
Roll
Nod
Shake
Vestibular apparatus is constantly in operation
Gravity
Vestibulo-ocular reflex
Anatomy
Located in the head
Same solid body as the eyes
Optimal to know the position of the head than the trunk
Otholith organs
Saccule
Utricle
Transduction
Otolith Organs
Semicircular organs
Senses linear acceleration
Haircells
Excitation is generated through gravity
Cells are linked to calcium rocks in the ear
Head moves in one direction, Rocks FOLLOW the direction of movement
Head bending backward causes Depolarisation
Head tilting forward causes hyperpolarisation
Senses vertical movement
senses Horizontal movement
Canals
Cupula
Ampulla
Hair cells
Crista
Filled with endolymph
Does not flow past the Cupula
Area in which contains the haircells and the cupula
Extend through the crista into the cupula
Functions
Inertia of endolymph produce across the cupula
Cupula is distorted through the movements of the endolymph
Excitation similar to that of otholith except
Works in pairs
Rotation
Depolarisation on one side
Hyperpolarisation on the oter
Hair cells moves in the OPPOSITE direction
Vestibular output
Vestibular cortex
Eye muscles
Body muscles
Perception of balance
Gaze stabilisation
Head to body stabilisaton
Vestibular - Ocular reflex
Clinical involvement
Motion sickness
Meniere's disease
Symptoms: Dizziness, Nausea, Vomiting, Sweating, rapid pulse
Causes: unusual combination of head and eye movements
Different conflicting sensory input upsets the nearby vestibular system
Symptoms: fluctuating nerve damage, vertigo, tinnitus, fullness of pressure in ear
Cause: probably increased volume and pressure of the endoymph