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Neurology Ch 9-10
Auditory System
| Term | Definition |
|---|---|
| Parts of the External Ear | -Pinna -External Auditory Meatus (Resonator) -Tympanic Membrane |
| Pinna | -External part of ear -Secondary Sound amplifier to middle ear. -If removed, person will have slightly reduced hearing. |
| External auditory meatus | - Ear canal - Where sound is carried through |
| Tympanic membrane | -Sound waves enter through the External auditory Meatus and vibrate this structure. -Where acustic energy is transferred into mechanical energy. -aka ear drum |
| Middle ear | -Located behind the tempanic membrane -Air-filled Cavity with ossicles called Malleus, Incus and stapes. -Where majority of sound amplification occurs -Converts acoustic to mechanical energy |
| Stapedial muscle | -Contracts to decrease vibration coming into ear to protect it. Contracts when sound to loud and when you speak |
| Stapedial reflex | -When sound too loud impulse goes from cochlea to brainstem. Neural signal then transferred through the facial CNVII to tell this muscle to contract |
| Oval window | opening into the inner ear |
| How energy goes from mechanical to hydrolic in the ear | As Stapes vibrates it puts liquid inside middle ear into motion. This is where the mechanical energy turns to hydrolic energy. |
| Overall Energy Change in ear | Acoustic-mechanical-hydrolic-neural stimuli |
| Cochlea | -Snail shell shaped structure that has 2.5 turns- is housed with in the temporal bone Has three fluid filled frequency specific cavities: 1) vestibuli 2) tympani 3) Scala media |
| Perilymph | -similar to cerebrospinal fluid -fills the vestibuli and tympani cavities of the Cochlea |
| Endolymph | -similar to extracellular fluid -fills the Scala media cavity of the Cochlea |
| Organ of corti | -Located in middle and incased in the Scala Media of the Cochlea. -Is full of frequency specific hair cells that move and transfer hydrolic energy turns back to mechanical through hairs and then into a neural stimulus. |
| Reissner’s Membrane | -aka Vestibular memebrane -Separates the scala media from scala vestibuli |
| Basilar Membrane | -Membrane located in the Cochlea -Separates the scala media form the scala tympani |
| Tectorial membrane | -Located on top of the Organ Corti -Thicker and thinner in some places and makes it frequency specific) |
| Pontimadulari junction | -where the pons and medula meet -level of the brainstem where CN VIII enters |
| Cochlear Nucleus | 1st nucleus in brainstem Where CN VIII terminates in the brain stem |
| Superior Olivary Nuclei (complex) | Receives bilateral innervation – mostly contralateral(Most of what you hear in right ear is received on left hemisphere and vice versa) |
| Lateral Lemniscus | -The primary ascending auditory pathway -Extends from Superior Olivary Nucleus to Inferior Colliculous |
| Inferior Colliculus | - Located in the mid brain - Passes auditory stimuli to the thalamus |
| Brachium of Inferior Colliculus | Primary output area of the Inferior Colliculus |
| Auditory Radiations | Carry information away from thalamus |
| Tonotopic Representation | -specific neurons in auditory cortex are responsible for different parts of the tectorial membrane in the Cochlea -The Cochlea, organ of corti, Auditory Radiations, Auditory Cortex are all frequency specific |
| Heschl's Gyrus Primary auditory Cortex | -Area 41 -Area of the Primary Auditory Cortex -located ontop of the Superior temporal lobe -Higher Frequencies in posteriomedial region -Lower Frequencies in Anterolateral region |
| Association Cortex Wernicke’s Area | -Area 22 -Connects what you hear with meaning -only in left hemisphere so sound we hear in left ear still processed as language to the left side through the corpus collosum, Therefore have bilateral speech perception areas but unilateral language area |
| Pure word deafness | -Leasion in Auditory Area that are specific to speech sounds -Person can still understand environmental sound like phone ringing but can’t understand words -Not a language problem, but speech discrimination problem. |
| Auditory Reflexes | -Pathways integrate visual and auditory information; mostly at the level of the brainstem -Coordinate head and eye movements toward sound - helps with balance |
| How do we know where sound is coming from | The timing of when the sound hits left or right ear helps discriminate sound location. If right in front of you hits ears at same time. |
| Can person with unilateral hearing lost locate sound? | No |
| Bilateral primary auditory cortex lesions result in: | 1)Profound loss of auditory discriminative skills 2)Impaired speech perception 3)Hearing loss |
| Unilateral destruction of primary auditory area results in | Little to no hearing loss- b/c we have info from 1 ear that goes to both hemispheres |
| Conductive Hearing Loss | Excessive Cerumen in canal, Otitis Media of Middle Ear |
| Sensorineural Hearing Loss | -Meniere’s disease (Inflammation of the Cochlea), Presbycusis hearing loss associated with aging (loose higher frequency perception) |
| Central Hearing Loss | Caused by a bilateral destruction of auditory cortex Pathology in cortex |
| Vestibular system | -Bony Labyrinth that helps maintain equilibrium, posture in dark and coordination -Parts: Saccule, Utricle & Semicircular Canals -Located in temporal bone next to the cochlea Position of fluid in canals gives information on movement and proprioception |
| Semicircular Canals | - Part of the vestibular system where stimulation of neurons occur |
Created by:
aramos139
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