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S & P
Vestibular System
| Question | Answer |
|---|---|
| What are the functions of the vestibular system? | ~To provide a subjective sensation when we move/are displaced in 3D space. ~To maintain upright body posture and control movements (balance). ~To control the extra-ocular muscles that move the eyes, keep visual world still during movement. |
| What are the stimuli for the vestibular system? | Input from the body & movements in the vestibular apparatus. There is not really an external stimuli. |
| Describe the Vestibular Pathway | ~Signals carried on vestibular portion of cranial nerve 8, vestibulocochlear n. ~Brainstem nuclei compare R & L inputs ~Ventro-postero-lateral thalamus ~Many cortical regions, but no clearly identified vestibular cortex. |
| What are the bilateral vestibular organs and where are they located? | Composed of semicircular canals (ducts) that sense angular rotational movement in 3 planes (head tilt & rotation) & otolith organs that sense linear movement (accel/deceleration). Located above & in between the cochlea and middle ear bones. |
| What are the otolith organs composed of? | ~Utricle: hair cells on floor, horizontal movements ~Saccule: hair cells on wall, vertical movements |
| Which duct is responsible for moving the head to say yes? | Anterior semi-circular duct (Pitch - y axis) |
| Which duct is responsible for moving the head to say no? | Lateral semicircular duct (Yaw - z axis) |
| Which duct is responsible for moving the head ear to shoulder? | Posterior semicircular duct (Roll - x axis) |
| What are the sensory receptor cells for the vestibular system? | Hair cells which are not normal neurons. There are many stereocilia and kinocilium. |
| For the vestibular system, where are the hair cells which transduce linear acceleration located? | Located in the maculae in utricle & saccule and convered with gelatinous otolith membrane (with otoconia) |
| For the vestibular system, where are the hair cells which transduce acceleration/head rotation located? | Located in the cristae in semicircular canal and convered with gelatinous cupula |
| What are the targets for the Vestibular pathway? | Will project motor commands to multiple areas. Targets include eye movement, limb extensor movement, cerebellum, & spinal cord. |
| Describe the vestibular ocular reflex (VOR) | Input to muscle of the eyes. Begins with detection of rotation (fluid moves r-l), then inhibition on one side & excitation on the other side of extraocular muscles, and finale compensating eye movement (l-r). |
| What are vestibular reflexes based upone? | Comparison of different signals coming from left & right vestibular apparatus; it is the asymmetry of firing between the two sides which drives the reflexes. |
| What is nystagmus? | Related to the VOR - the pathway is not well understood, but cortex is involved. Basically, it is the slow tracking of the eyes to edge of orbit and the quick return to straight ahead. |
| What is Meniere's disease? | It's not always understood why this happens to some people, but the endolymphatic sac becomes enlarged by increased fluid pressure and ballooned out membranes. This causes symptoms of vertigo, nausea, tinnitus and hearing loss. |
| Caloric nystagmus | Test of the vestibular reflexes through hot and cold water inserted in the ear. COWS: Cold Opposite, Warm Same. |
Created by:
cassidylm34
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