Ear

• Division of the central nervous system:

  motor output (somatic and autonomic)

  Sensory system
• Outer, middle and inner ear

  A) pinna

  B) auditory canal

  C) skull bone

  D) tympanic membrane

  E) oval window

  F) round window

  G) eustachian tube

  H) cochlea

  I) auditory nerve to brain

  J) malleus

  K) incus

  L) stapes

  M) semicircular canals

  
• Role os semicircular canal

  balance
• Middle ear

  A) malleus

  B) superior ligament of malleus

  C) incus

  D) posterior ligament of incu

  E) stapes of oval window

  F) facial (vii) nerve

  G) round window

  H) tensor tympani muscle

  I) auditory tube

  J) middle ear

  K) eardrum

  L) stapedius muscle

  M) external auditory canal

  N) anterior ligament of malleus

  O) lateral ligament of malleus

  
• Inner ear

  A) bony labyrinth (contains perilymph)

  B) membranous labyrinth (contains endolymph)

  C) utricle

  D) endolymph sac

  E) vestibule

  F) saccule

  G) cochlea

  H) cochlea duct

  I) oval window

  J) secondary tympanic membrane in round window

  K) ampulla of semicircular duct

  
• What part contains perilymph?

  vestibular canal (scala vestibuli) and tympanic canal (scala tympani)
• what part contains endolymph?

  cochlear duct (scala media)
• What is the difference between perilymph and endolymph?

  Endolymph contains form K+
• Cochlear

  A) cochlea duct

  B) bone

  C) auditory nerve

  D) organ of corti

  E) tympanic membrane

  F) vestibular canal

  
• Basilar membrane:

  Organ of corti rests on it

  • long collagen (floppy) fibres low frequences are detected by apex
  • short collagen (stiff) fibres detect high frequences by the oval
• organ of corti: hair cells that are sensitive to sound waves and vibrations
• Sound frequencies heard by humans

  
• Organ of corti:

  • 3 rows of outer hair cell
  • 1 row of inner hair cell
  • 40-80 stereo cilia on apical surface of each hair cell which project into tectorial membrane

  Fluid movement in cochlear duct causes part of basilar membrane to vibrate which causes stimulation of hair cells which active sensory neuron- sends a message to the brain

  A) basilar membrane

  B) hair cells

  C) axons of sensory neurons

  D) to auditory nerve

  E) tectorial membrane

  
• How is mechanical stimulation converted to electrical signals

  1. basilar membrane vibration
  2. stereocilia detect movement
  3. depolarisation of hair cells
  4. neurotransmitter release
  5. activation of sensory neurones
  6. message conveyed to brain via cochlear branch of vestibulo-cochlear nerve
• What are cochlea sound emissions?

  Otoacoustic emissions - vibrations of outer hair cells that occur in response to sound waves and to signals from motor neurons, as they shorten, this stiffens the tectoria; membrane (enhancing movement of basilar membrane)
• Cochlea

  A) utricle

  B) stapes of oval window

  C) saccule

  D) scala vestibuli

  E) cochlea

  F) scala tympani

  G) cochlea duct

  H) scala vestibuli

  I) helicotrema

  J) basilar membrane

  
• What is balance dependent on?

  vestibular apparatus
• what is the vestibular apparatus?

  semicircular ducts
• Semicircular canals:

  bony on the outside

  endolymph filled membrane inside
• Macula:

  (one each in utricle and saccule) - detect head position, acceleration and deceleration

  Two types of cell: hair cells and supporting cells
• Macula

  A) supporting cells

  B) hair cells

  C) otoliths

  D) otolithic membrane

  
• Hair cells:

  stereocilia move due to movement of head

  transduction channels open leading to depolarisation (close leads to repolarisation)

  signal sent via vestibular branch of vestibulocochlear nerve
• Semicircular ducts (canals)

  • detection of rotational acceleration or deceleration
• cupula and ampulla:

  send nerve impluses to motor area to ensure you keep balance

  found in semicircular ducts