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22 Cards in this Set

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weber test: how, what does it mean

place tuning fork on vertex of skull; if unilateral conductive loss --> vibration is louder in affected ear; if unilateral sensorineural loss --> vibration is louder in normal ear

rinne test: how, what does it mean

place tuning fork on mastoid process (bone conduction) until vibration is not heard, then place fork in front of ear (air conduction); if unilateral conductive loss --> no air conduction after bone conduction is gone; if unilateral sensorineural loss --> air conduction present after bone conduction is gone (this is what would also be seen in a normal ear and basically its saying "we know that there is hearing loss but the sensorineural hearing loss is not full hearing loss yet" so do this to rule out conductive hearing loss so all that's left is sensorineural hearing loss

hyperacusis

increased sensitivity to loud sound; can be due to Bell's palsy where the stapedius is impaired

presbycusis

loss of hear cells a the base of the cochlea (sensorineural hearing loss were you loose high frequencies first)

the ampulla respond to what

ampulla are in the semicircular canals; angular acceleration

the utricle and saccule respond to what

linear acceleration and gravity

endolymph composition

high K+ and low Na+ produced by the stria vascularis (needed for hair cell function)

trace an auditory signal

external auditory meatus --> tympanic membrane --> malleus --> incus --> stapes --> oval window --> scala vestibuli --> scala tympani --> cochlear hair cells in scala media (or to round window) --> spinal ganglion (just cell body here) --> pontine medullary junction --> synapse on cochlear nucleus (of 8) --> then bilaterally ascends to the superior olivary nucleus where it synapses in a higher pons region --> travels in the lateral lemniscus to the inferior colliculus of the midbrain where it synapses --> medial geniculate body in the thalamus where it synapses --> superior temporal gyrus of the cerebral cortex (primary auditory cortex); only ispilateral loss if lesion at cochlear nucleus or before

trace a cochlear signal

hair cells in ampulla or utricle or saccule --> cell body in vestibular ganglion --> enters brainstem at the pontomedullary junction --> 4 vestibular nuclei some of which synapse with the lateral vestibulospinal tract (does down to muscles to maintain upright posture)

vestibular oculo reflex: with a head turn to the right when you want to keep something centered on your foveas

head movement stimulates the vestibular labyrinth on the right and therefore the right vestibular nerve (increases firing rate) and therefore the right vestibular nuclei; vestibular nuclei send axons through the medial longitudinal fasciculus that then make the eyes look to the left to keep the object centered (abducens nucleus on the left side (abduct left eye) and oculomotor nucleus on the right side (adduct right eye))

what happens if you lesion the left vestibular nuclei

the left and right balance each other so if you nock out left, then right is at too high of a rate and makes you slowly look to the left (see above) but the brain is like 'what? no' and snaps the eyes back to the right; this is called a right nystagmus (the violent phase is the named phase); so right nystagmus= left vestibulonuclear lesion

what is the caloric test and how do you do it

stimulates the horizontal semicircular ducts; can be used as a test of brain stem function in unconscious pts; normal results= COWS (cold opposite nystagmus, warm same nystagmus)

what is vertigo: peripheral versus brain stem lesion

the perception of rotation; usually severe in peripheral disease and mild in brain stem disease of vestibular regions; chronic vertigo suggests a central lesion

meniere disease: what is it

characterized by abrupt, recurrent attacks of vertigo lasting minutes to hrs; accompanied by deafness or tinnitus and is usually in one ear; nausea and vomiting may occur; due to distention of fluid spaces in the cochlear and vestibular parts of the labyrinth

what about voluntary ocular movement: take me through moving the eyes to the right voluntarily

cerebral cortex frontal eye fields (area 8) activated on the left --> descends into the brainstem and synapses on the contralateral paramedian pontine reticular formation (PPRF) (it's basically in the abducens nucleus) --> projects to the abducens nerve where it synapses; from here one path is to the ipsilateral lateral rectus (by way of the abducens nerve) to cause abduction of the right eye); other path is across the medial longitudinal fasciculus (this is a high speed tract) to the oculomotor nucleus where it synapses --> oculomotor nerve to the left medial rectus muscle to adduct the left eye

what happens in a lesion of the right abducens nucleus

same thing as saying a PPRF lesion; neither eye can look to the right; also have right side bell's palsy because of the hooking of CN7 around CN6

what happens in a lesion of the left MLF

this is commonly called an internulear (between nuclei) opthalmoplegia; left eye cannot look right (cannot adduct) (convergence is still intact which lets you distinguish an MLF lesion from an oculomotor lesion); MLF is high speed= heavily myelinated= SEE THIS IN MS

what happens in a lesion of the left frontal eye field

neither eye can look to the right; R lower face weakness due to proximity of the frontal eye fields to the corticobulbar tracts

abducens nucleus lesion versus abducens nerve lesion

nucleus is right on top of PPRF so damage to nucleus means neither eye can look to the ipsilateral side (probably also have an ipsilarteral facial paralysis because of CN7); nerve is out of the nucleus and so you just can't abduct the ipsilateral eye

blood supply to the medulla

medial is anterior spinal artery; lateral is PICA

blood supply of the pons

medial pons is paramedian; lateral is AICA (CN7, 8) or superior cerebellar artery

blood supply to midbrain

all of it is by posterior cerebral artery