Hearing
• OUTER EAR (PINNA) = amplifies and directs the sound
• EAR DRUM (TYMPANIC MEMBRANE) = vibrates with the external sound
• THE MIDDLE-EAR CAVITY (filled with air) = contains three small bones, malleus (hammer), incus (anvil), and stapes
(stirrup), which amplify the movement of the eardrum onto the oval window
• THE INNER EAR (COCHLEA) = is filled with a fluid, endolymph, which vibrates with the movement of the oval
window so that the sound can be detected by sensory receptors
• Exposures the middle ear to atmospheric pressure by connecting it to the pharynx
• Normally closed, but opened during yawning, swallowing, or sneezing
• Throat infections can block the eustachian tube and result in fluid build-up in the middle ear
• Bacteria are trapped in the middle ear can cause an ear infection (otitis media)
• Divided lengthwise by the cochlear duct, which is filled with endolymph
• On either side of the cochlear duct are compartments filled with another fluid, perilymph:
i. Scala vestibuli
ii. Scala tympani
• The cochlear duct rests upon the basilar membrane
• On the basilar membrane, inside the cochlear duct, is the organ of Corti, which contains the auditory receptors
• Different parts of the basilar membrane resonate at different frequencies of sound
• The adjacent section of the organ of Corti will vibrate with the basilar membrane
• The receptor cells of the organ of Corti are called hair cells. They are mechanoreceptors equipped with 50-100 stiff
hair-like stereocilia at one end, which are covered by the tectorial membrane
• When the stereocilia bend, ion channels open, and the membrane is depolarised
• Hair cells are non-neural
• They form synapses with primary auditory neurones, using glutamate as a transmitter
• Axons from primary auditory neurones gather to form the cochlear nerve
• The cochlear axons end in the brainstem, where they form synapses with interneurons where processing and
integration takes place
• A multineuronal pathway transmits the information to the thalamus and further to the auditory cortex
• Initial processing takes place in the cochlea for:
i. Pitch
ii. Loudness
Integration of Physiological Systems Page 1
• OUTER EAR (PINNA) = amplifies and directs the sound
• EAR DRUM (TYMPANIC MEMBRANE) = vibrates with the external sound
• THE MIDDLE-EAR CAVITY (filled with air) = contains three small bones, malleus (hammer), incus (anvil), and stapes
(stirrup), which amplify the movement of the eardrum onto the oval window
• THE INNER EAR (COCHLEA) = is filled with a fluid, endolymph, which vibrates with the movement of the oval
window so that the sound can be detected by sensory receptors
• Exposures the middle ear to atmospheric pressure by connecting it to the pharynx
• Normally closed, but opened during yawning, swallowing, or sneezing
• Throat infections can block the eustachian tube and result in fluid build-up in the middle ear
• Bacteria are trapped in the middle ear can cause an ear infection (otitis media)
• Divided lengthwise by the cochlear duct, which is filled with endolymph
• On either side of the cochlear duct are compartments filled with another fluid, perilymph:
i. Scala vestibuli
ii. Scala tympani
• The cochlear duct rests upon the basilar membrane
• On the basilar membrane, inside the cochlear duct, is the organ of Corti, which contains the auditory receptors
• Different parts of the basilar membrane resonate at different frequencies of sound
• The adjacent section of the organ of Corti will vibrate with the basilar membrane
• The receptor cells of the organ of Corti are called hair cells. They are mechanoreceptors equipped with 50-100 stiff
hair-like stereocilia at one end, which are covered by the tectorial membrane
• When the stereocilia bend, ion channels open, and the membrane is depolarised
• Hair cells are non-neural
• They form synapses with primary auditory neurones, using glutamate as a transmitter
• Axons from primary auditory neurones gather to form the cochlear nerve
• The cochlear axons end in the brainstem, where they form synapses with interneurons where processing and
integration takes place
• A multineuronal pathway transmits the information to the thalamus and further to the auditory cortex
• Initial processing takes place in the cochlea for:
i. Pitch
ii. Loudness
Integration of Physiological Systems Page 1
