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Ear (How to perceive sound (Frequency (Below hearing: helicotrema, X…

- - - - Utricle
        
        Oval window located here
      - Saccule
      - Contained in maculae
    - - Static equilibrium eg. lift/car
  - - - Anterior: Yes
      - Lateral: No
      - Posterior: Dunno
    - - Each canal contains part of membranous labyrinth
      - Hair cells (receptors) in ampulla of canals
      - Depending on which way cilia bends, tell brain which way head is tilting, fluid will have a delay bcos need time to travel
      - Kinocilum as big spoon; Stereocilia as small spoons embedded in gelatinous matrix (capula)
      - Excitation: hair cells depolarised when stereo bent toward kino
      - Inhibition: Hair cells hyperpolarised when stereo bent away from kino
      - Mvm of endolymph: bending of capula
      - Vestibular branch of vestibulocochlear nerve carries impulse to cerebellum
  - - - Base, series of turns to apex
      - Spiral shaped bony labyrinth coiled around modiolus
      - Cochlear branch of vestibulocochlear nerve enters inner ear via internal auditory meatus
      - Chambers
        
        Vestibular duct (Perilymph)
        
        starts at oval window
        
        Tympanic duct (Perilymph)
        
        ends at round window
        
        Cochlear duct (Endolymph)
      - Other parts
        
        Spiral ganglion: contains cell bodies of sensory neurons, exits at cochlear branch of vestibulocochlear nerve
        
        Vestibular membrane: separates cochlear from vestibular duct
        
        Basilar membrane: separates cochlear, tympanic duct ; influence hair cells on top. Push hairs against tectorial membrane --> Fire off action potential
        
        Spiral organ of Corti
        
        Sits on basilar membrane
        
        Hair cells in cochlea arranged in rows
        
        Stereocilia interact w overlying tectorial membrane
        
        Hairs DO NOT REGENERATE: loss of hearing
    - - Tympanic membrane will vibrate to same freq, stiffness and thickness of basilar membrane
      - High freq sound-> high pitch--> short wavelength
      - Low freq sound--> low pitch--> long wavelength, easier to displace
      - To determine freq: which hair cells in which region of cochlea is displaced
    - - Energy determines intensity of sound wave
      - Perception: degree of displacement of basilar membrane, no. of hair cells that are stimulated
  - - - Canals inside temporal bone filled w perilympth, continues w CSF
    - - Membranous tubes filled w endolymph
- - - - Head, neck, manubrium
      - Saddle joint
    - - Body, short process, long process
      - Ball & socket
    - - Head as site of articulation, footplate covers oval window
  - - - Runs along auditory canal
      - Inserts on malleus
      - Stiffens tympanic membrane, restricts mvm
      - Trigeminal nerve
    - - Posterior wall of middle ear
      - Inserts on stapes
      - Restricts mvm of stapes at oval window
      - Facial nerve
- - - - Block normal transfer of vibrations to inner ear
      - BCOS wax build up in EAM, perforation of tympanic membrane, immobilisation of ossicles, middle ear (otitis media), ossicle infections
      - Bone conduction methods most effective on this
    - - Problem w cochlea/nerve pathway
      - Noise-induced damage to hair cells, drug-induced damage to hair cells, bacterial infectoin , degeneration of cochlear nerve, damage to auditory cortex
  - - - Sound waves via tympanic membranes, ossicular chain
    - - Vibrations thru bones--> directly to cochlea
      - Examples
        
        Beethoven biting rod connected to piano
        
        Headphones for aircraft carriers--> try to block out as much as possible
        
        Underwater communication
      - Skill conducts lower freq better--> voice sounds deeper when you listen to it recorded
- - - - Oval window
      - Round window
      - Auditory tube
        
        Infants vs. adults differences
        
        Passageway b/w middle ear, nasopharynx
        
        Cartilaginous & osseous
        
        Equalise pressure in middle ear
        
        Opened by palatini muscles
        
        Provides passage for micro-organisms--> otitis media (middle ear infection-bacterial/viral, puss, fluid, inflammed); complications
- - - - Functions
        
        Protects opening of external acoustic canal
        
        Cartilaginous w overlying skin
        
        Collect sound
        
        Provides directional sensitivity. Elastic cartilage will recoil
      - Structure
        
        Continuous w cartilage of external auditory meatus
    - - Funneled from auricle into this
      - Cereminous glands
        
        Run along EAM
        
        Secrete waxy material
        
        Sticky
        
        Keeps foreign objects, insects out of tympanic membrane
        
        Slows growth of micro-organisms
        
        Too much: can cause temporary hearing loss. Sounds muffled at first--> swell--> infection
    - - Structure
        
        S-shaped tube, ~25mm long, 8mm wide
        
        30-50% of meatus (lateral) is cartilaginous, rest is bony.
        
        Meatus directed slightly downward to avoid collection of foreign particles
      - Function