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Midterm

PSL440Y1 Study Guide - Midterm Guide: Posterior Parietal Cortex, Premotor Cortex, Hemispatial Neglect


Department
Physiology
Course Code
PSL440Y1
Professor
Doug Hutchinson
Study Guide
Midterm

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Pathophysiology,of,Hearing,
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- categories!of!hearing!disorder:!!
o Conductive!
§ Ex.!Otitis!media!otosclerosis!
§ Reduced!signal!reach!
o Cochlear!
§ Ex.!Age!related!hearing!loss!
§ Direct!damage!to!cochlear!
§ Noise&induced!hearing!loss!
o Retro-cochlear/Central!
§ Ex.!Acoustic!neuroma!
§ Auditory!neuropathy!or!
processing!disorder!
- Cochlear!areas!of!maximum!vulnerability!
o Stria!vascularis!
§ Ex.!Hypoxia!
§ Chronic&noise!
§ Presbycusis!à!loss!of!hearing!
that!gradually!occurs!in!most!
individuals!as!they!grow!older.!
o Haircells!
§ Ex.!Ototoxic!drugs!–!
aminoglycoside!antibiotic,!old!age!
§ acoustic&trauma&
o Inner!haircell!synapse!
§ Ex.!Drugs!such!as!aspirin,!hypoxia!
§ Chronic&noise!
- Presbycusis:"strial!function!reduces!electrical!
driving!force!for!haircell!activation!
- Most!cochlear!damage!likely!occurs!first!at!the!
cochlear!afferent!nerve!terminal!
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Sound,Transduction,
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- Sound!vibrations!from!an!object!cause!vibrations!in!air!molecules,!
which!in!turn,!vibrate!your!ear!drum.!!
- The!movement!of!the!eardrum!causes!the!bones!of!your!middle!ear!
(the!ossicles)!to!vibrate.!!
- These!vibrations!then!pass!in!to!the!cochlea,!the!organ!of!hearing.!!
- Within!the!cochlea,!the!hair!cells!on!the!sensory!epithelium!of!the!
organ!of!Corti!bend!and!cause!movement!of!the!basilar!membrane.!!
- The!membrane!undulates!in!different!sized!waves!according!to!the!
frequency!of!the!sound.!!
- Hair!cells!are!then!able!to!convert!this!movement!(mechanical!
energy)!into!electrical!signals!(graded!receptor!potentials)!which!
travel!along!auditory!nerves!to!hearing!centres!in!the!brain.!
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Sound,Localization,
- Three!main!cues!for!sound!localization:!!
1. interaural!sound!intensity!difference!
- sound!from!right!causes!louder!sound!in!right!ear!(head!has!a!sound!shadow)!
- e.g.!if!sound!is!coming!from!right!is!at!10!kHz!(high!freq),!then!sound!reaching!opposite!ear!
will!probably!be!6-9db!less!than!right!ear!
- mediated!by:!lateral,nucleus!of!the!superior,olivary!complex!
2. interaural!time!/!phase!difference!
- sound!from!right!reaches!right!ear!before!it!reaches!the!left!ear!
- mediated!by:!medial,nucleus!of!the!superior,olivary!complex!
3. monaural!cues;!spectral!modification!!
- The!head,!pinna,!and!ear!canal!modify!frequency!components!differently!
- (note!also,!dynamic!aspects:!moving!pinnae/head;!orientation)!
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Superior,Olivary,Complex,
Lateral!nucleus!of!Superior!Olive!(LSO)!
- Neurons!receive!input!from!both!ears!
- responses!are!of!the!EI!type!(excited!by!input!from!one!ear,!inhibited!by!input!from!the!other!ear)!
- Role!in!sound!localization!!
- Detects!interaural!sound!intensity!differences!
- High!CF!neurons!!
- Relatively!large!in!animals!with!small!heads!!
- Output!to!inferior!colliculus!(midbrain)!
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Medial!nucleus!of!the!superior!olive!(MSO)!!
- Role!in!sound!localization!!
- Direct!input!from!AVCN!!
- Detects!interaural!time!or!phase!difference!!
- Relatively!large!in!animals!with!large!heads!(e.g.!humans)!!
- Output!to!the!inferior!colliculus!(midbrain)!
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