1. What are the functions of the human ear?
  • hearing
  • balancing
  • How are the structures of the human ear suited to perform the function of hearing?
  • shape of the external ear/pinna allows collection of sound waves and channels them down the auditory canal/auditory mateus
  • auditory canal is a tube that concentrates and directs sound waves to tympanic membrane/ tympanum/eardrum
  • Eardrum is thin and tight. It sets into vibration/vibrates/converts sound waves into vibrations
  • the vibrations are transmitted to the ear ossicles/malleus, incus and stapes that amplify the sound vibrations
  • the vibrations are then transmitted to the fennestra ovalis/oval window
  • Oval window is a membrane which amplifies/transmits vibrations to the fluids (perilymph and endolymph) then to cochlea.
  • The cochlea is coiled to occupy a small space and accommodate a large number of sensory cells
  • The sensory cells/hairs (in the cochlea) are set into vibrations/stimulated producing nerve impulses in the auditory nerve
  • Impulses in the auditory nerve are transmitted to the brain for interpretation for hearing
  • Eustachian tube connects the inner ear to the throat. It equalizes air pressure in the middle ear with the atmospheric air pressure (in outer ear)
  • Fennestra rotundus/round window dissipates/discharges/discards vibrations from inner ear to middle ear

iii) Explain how the structure of the human ear performs the function of balancing

  • there are three semi-circular canals/utriculus/succulus/vestibular apparatus arranged in planes at right angles to each other
  • at the end of each canal is a swelling called ampulla which contains receptors
  • the movement of the head causes movement of the fluid/endolymph in at least one canal
  • the fluid movement causes stimulation of the receptors/sensory hairs
  • sensory impulses are generated
  • the auditory nerve transmits the impulses to the brain for interpretation for the position of body/posture/balance

iv) State what would happen if the auditory nerve was completely damaged

  • deafness
  • loss of body balance

impulse not transmitted to the brain