Sound Transduction

• Which part of the inner ear is responsible for sound transduction?

  Cochlea
• Where is the tectorial membrane?

  Sits on top of hair cells within the cochlea
• Where is the basilar membrane?


  Sits beneath hair cells in the cochlea
• What is the function of outer hair cells?

  Change the sensitivity of sense of hearing (e.g. if you want to focus on a certain sound)
• Sound waves are computed into electrical information through organ of Corti.
• What is the auditory sensory organ?

  organ of Corti

  • within the scala media (in cochlea)
• Where is endolymph found?

  Scala media
• Where is perilymph found?

  Scala tympani

  Scala vestibuli
• Sound waves in external acoustic meatus → tympanic membrane vibrates → ossicles amplify → movement of oval window → sound waves through endolymph → basilar membrane vibrates → movement of stereocilia on hair cells → opens K+ channels → depolarisation → opens voltage-gated Ca+2 channels & glutamate release → projections to auditory branch of CN VIII → terminate on cochlear nuclei → cochlear neurons project to superior olive (ipsi- & contralaterally) in pons → through lateral lemniscus to inferior colliculus (in midbrain) → to medial geniculate nucleus (MGN) in thalamus → primary auditory cortex
• Cell bodies of afferent neurons comprise the spiral ganglion.
• Fill in the blanks

  A) Scala tympani

  B) Scala media

  C) Scala vestibuli

  D) Tectoral membrane

  E) Basilar membrane

  F) Organ of Corti

  G) Spiral ganglion

  
• There is a topographic map on frequencies in the cochlea, along the basilar membrane.

  
• What is the superior colliculus responsible for?

  Visual reflex movements
• What is the inferior colliculus responsibel for?

  Auditory reflex movements
• What is the difference between the roles of the primary & secondary (association) auditory cortices?

  Primary auditory cortex -> hearing sound

  Secondary (association) auditory cortex -> bringing meaning to sound
• What is Wernicke's area?

  Specialised part of association auditory area

  Responsible for language processing
• How does Wernicke's aphasia present?

  Deficit in UNDERSTANDING language
• There is a topographic map of sound frequency on the primary auditory cortex, that matches the topographic map on the cochlea.
• Broca's & Wernicke's area are usually located on the left, but not always.
• What is Broca's area?

  Specalised part of premotor cortex

  Controls laryngeal region -> responsible for the production of speech
• Fill in the blanks

  A) Oval window

  B) Round window

  C) Cochlea

  D) Auditory nerve

  E) Vestibulat nerve

  
• What is the role of the round window?

  Equalize pressure in the cochlea
• Fill in the blanks

  A) Scala vestibuli

  B) Scala media

  C) Scala tympani

  D) Outer hair cells

  E) Inner hair cells

  F) Basilar membrane

  G) Tectorial membrane

  H) Spiral ganglion

  
• Fill in the blanks

  A) Tectorial membrane

  B) Stereocilia

  C) Outer hair cells

  D) Inner hair cells

  E) Basilar membrane

  F) Afferent axons

  G) Organ of Corti