32 VESTIBULAR PHYSIOLOGY Flashcards
Maintenance of balance involves three aspects:
Vestibular system, proprioception, sight
What part of the brain atrophies if you take away the vestibular system
The hippocampus. Involved in spatial memory (as well as long and short term memory)
What are the two kinds of motions the vestibular system detects
Linear and angular
What is the consequence of chronic gradual loss of vestibular function
May see no effect as the central nuclei compensate
Define vertigo
Perception of motion when there is no motion
Why does the vestibular system not work in space
Because it relies on gravity
What are the outputs for vestibular nuclei
Cerebral cortex, cerebellum, oculomotor cranial nerves, autonomic nervous system, pyramidal tract
What are the three sensory organs in the ear
The otolith organs, saccula and utricle and the semicircular canals
What are the sensory cells in the otolith organs called
Macula
What sensory organs detect linear movement
The otolithic organs- utricle and saccule
What detect angular movement
The semicircular canals (ampullae)
How do the otolithic organs work
Sensory epithelium of the otolithic organs is called the macula which consists of hair cells and supporting cells. Above the macula is a gelatinous layer and above this a fibrous layer called the otolithic membrane in which there are crystals called otoconia embedded. The otoconia make the otolithic membrane heavier than the structures and fluid surrounding it so when the head tilts gravity causes the membrane to tilt and there is a shearing motion between the otolithic membrane and the macula resulting in excitation of hair cells
How do the semicircular canals work
At the base of each semi circular canal are ampulla which house the sensory epithelium called crista. Hair bundle extend out of the crista into a gelatinous mass called the cupula that forms a barrier so that fluid cannot pass. The cupula is distorted with movements of the endolymph which moves via inertia when angular head movements occur (with linear movements there is equal forces on each side of the cupulla so hair cells are not displaced)
Describe the pairing relationship in semicircular canals
Each canal is paired with the canal on the opposite side that has its hair cells arranged in the opposite direction. When one is stimulated the other is hyperpolarized. this results in a system that provides information about the rotation of the head in any direction. It thus gives the brain an indication about what direction you are going in.
What are the longest stereocilla called
Klinocillium
