ear and hearing

• external ear is consists of the

  pinna, auditory canal, ear drum (tympanic membrane)
• middle ear contains 3 of the smallest bones in the human body, these are

  malleus, incus and stapes
• inner ear consists of cochlea, vestibular apparatus
• cochlea contains 


  organ of corti
• organ of corti is responsible for

  detecting sound waves
• vestibular apparatus includes 


  semi-circular canals that give us sense of balance
• sound waves are focused and collected by the

  auditory canal
• once sound waves pass down the auditory canal, the ear drum

  vibrates
• vibrations on the ear drum pass over the 3 bones to the

  oval window which connects with the cochlea
• tensor tympani muscle function

  mediate efficiency of the sound transmission from the eardrum to the oval window
• tensor tympani muscle will change the tension between the bones so that the efficiency transmission of sound will change to protect the inner ear from damage, and so even very quiet noise can be transmitted
• the cochlea looks like a snail
• cross section of the cochlea

  labels

  A) cochlear duct

  B) bone

  C) auditory nerve

  D) vestibular canal

  E) tympanic canal

  F) organ of corti

  
• vestibular canal AKA 


  scala vestibuli
• cochlear duct AKA


  scala media
• tympanic canal AKA 


  scala tympani
• perilymph is fluid of the vestibular and tympanic canals
• endolymph is fluid in cochlear duct
• endolymph contains more _ than perilymph 


  K+
• cochlear duct contains the

  basilar membrane and thee organ of corti
• the organ of corti is located on the basilar membrane
• there are tiny hair cells that project of the top surface of the organ of corti
• inner ear

  labels

  A) oval window

  B) cochlea

  
• middle ear

  labels

  A) malleus

  B) incus

  C) stapes

  D) eardrum

  
• sound travels better through fluid than air
• long hairs with low frequencies
• short hairs with high frequencies
• basilar membrane vibrates the hair cells (stimulates them) causing them to pass on stimulus to the 


  auditory nerve
• auditory nerve activates the sensory neurons
• organ of corti

  labels

  A) tectorial membrane

  B) basilar membrane

  C) hair cells

  D) axons of sensory neuron

  E) signal send to auditory nerve

  
• how does the vibrations get turned into our perception of sound?

  stereo cilia (consist of actin filaments sticking up from the surface of the hair cells) detect movement, stimulate and pass the signal to the auditory canal
• mechanical to electrical signals

  1. basilar membrane vibrates
  2. stereocilia detect movement
  3. depolarisation of hair cell
  4. neurotransmitter released
  5. activation of sensory neurones
  6. message conveyed to the brain via cochlear branch of vestibulo-cochlear nerve
• oval window is pushed in and out by the stapes
• round window moves in and out in sympathy at the opposite end to the stapes
• basilar membrane

  labels

  A) round window

  B) tympanic canal

  C) basilar membrane

  D) cochlear duct

  E) oval window

  F) stapes

  G) vestibular canal

  
• how does a cochlear implant work?

  • electrode into the cochlea
  • electrical signal can be sent
  • electrode is connected to receiver inside the skull
  • outside skull has hearing aid with transmitter
  • hearing aid picks up sound
  • transmitted to receiver
  • electrode stimulates auditory nerve in same region hair cells would detect it
• balance is dependent on

  vestibular apparatus
• vestibular apparatus consists of

  utricle, saccule and 3 semi-circular canals
• semi-circular canals are 


  bony on the outside and contain endolymph in their membrane
• physiology of balance

  labels

  A) semi-circular ducts

  B) utricle

  C) saccule

  D) cochlea