Audition

Question 1

Describe the anatomy of the Ear. Inner, outer and middle.

Answer 1

Outer Ear

• External Auditory Meatus
• Function: Improves transfer of sound energy to eardrum and sound localization

Middle Ear

• Ossicles: malleus, incus and stapes
• Muscles of the middle ear: tensor tympani and stapedius
• Oval Window
  
  • Function: Converts sound pressure waves to vibration of fluid

Inner Ear

• Contains the Cochlea (auditory system) and the Vestibular Apparatus (vestibular system)
• Cochlea
  
  • Contains 3 fluid-filled chambers
    
    • Scala Vestibuli and Scala Tympani filled with Perilymph
    • Scala Media (cochlear duct) filled with Endolymph
  • Contains Organ of Corti
    
    • Contains Auditory Receptors (Hair Cells) attached to Basilar Membrane
• Basilar Membrane
  
  • Contains Hair Cells that bend and cause Action Potential down CN VIII

Question 2

What is the auditory pathway?

Answer 2

Auditory Pathway

• Sound vibration gathered in Outer Ear and travels down ear canal
• To Middle Ear and Tympanic Membrane (Ear Drum)
• Sound causes vibration of Ossicles
• Movement of Stapes causes vibration of Oval Window
• Pressure waves generated in Perilymph and distort Basilar Membrane
• Hair Cells on the Basilar Membrane bend to produce an Action Potential
• Impulse moves along CN VIII to…
  
  • Superior Olivary Nucleus in Brainstem to…
  • Inferior Colliculi (auditory processing) in Brainstem to…
  • Medial Geniculate Nucleus in Thalamus to…
  • Primary Auditory Cortex and Secondary Auditory Association Cortex to Tertiary PMAC (from Parietal and Occipital as well)

Question 3

Where does sound go and what areas are responsible?

Answer 3

Auditory Processing Areas

Cortical areas processing hearing and speech

• Primary Auditory Cortex for initial reception
• Association Areas- for fine tuning/ discrimination
• Wernicke’s Area- left hemi- sounds from language (understanding language)
• Broca’s Area- output language and speech (speaking)
• Arcuate Fasciculus AKA Superior Longitudinal Fasciculus- connects Wernickes and Broca’s
• Temporal lobe
  
  • Analysis of complex sounds
  • Localization of sounds
  • Selective attention to sounds
  • Discrimination of auditory patterns (music, cadence, rhythm)

Question 4

What are some hearing deficits?

Answer 4

Hearing Deficits

• Conductive Deafness
  
  • Vibrations in Outer and Middle Ear are disrupted
  • Common Causes
    
    • Otitis media (inflammation)
    • Wax buildup
    • Perforation of tympanic membrane
• Sensorineural deafness
  
  • (more serious) Injury to Inner Ear, Auditory Receptors, Cochlear Nerve or Brain
  • Common Causes
    
    • Acoustic neuroma (benign tumor)- Vestibular/ balance afffected. Can be from loud noises
    • Acoustic trauma (loud noise exposure)

Question 5

How do you test CN VIII? What is the Rinne Test?

Answer 5

Auditory Screening of CN VIII

• Rinne Test
  
  • Place vibrating tuning fork on mastoid bone
  • When no longer hears sound, move to 1” from ear canal
• Normal Response
  
  • Hear through air conduction after no longer through bone conduction
  • Hearing louder by air conduction than bone conduction
• Dysfunction
  
  • Volume is reduced in both air and bone conduction and indicates sensorineural hearing loss
  • Hearing longer through bone conduction indicates air conduction hearing loss

Question 6

How do you test CN VIII? What is the Weber Test?

Answer 6

Auditory Screening of CN VIII

• Weber Test
  
  • Place vibrating tuning fork in middle of forehead and ask where sound is coming from
• Normal Response
  
  • Sound is heard through bone conduction and reports hear from both ears
• Dysfunction
  
  • Sound heard in affected ear due to unilateral conductive hearing loss
  • Sound heard in unaffected ear due to unilateral sensorineural hearing loss