Anatomy & Physiology Overview - The Ear
Pinna (auricle) - visible part of the ear outside of the head.
Ceruminous glands - specialized sudoriferous glands (sweat glands) located subcutaneously in the external auditory canal. They produce cerumen (earwax) by mixing their secretion with sebum and dead epidermal cells.
Tympanic membrane - vibrates in response to sound waves
Malleus, incus and stapes - 3 small bones that transmit vibrations to each other
Mechanoreceptor for hearing and balance
Vesibular apparatus - balance
• Organ of Cor - sensory epithelial cell
Perilymph = similar in compositon to plasma – Na+
Organ of Cor: contains hair cells – move due to pressure waves
50-100 stereocilia on each cell
Longest embedded in tectorial membrane
In the cochlea that the vibrations transmitted from the eardrum through the tiny bones are converted into electrical impulses sent along the auditory nerve to the brain.
The cochlea is a tapered tube which circles around itself
The basilar membrane divides the tube lengthwise into two fluid-filled canals joined at the tapered end.
ossicles transmit vibration to the cochlea where they attach at the oval window
resultant waves travel down the basilar membrane where they are “sensed” by 16-20,000 hair cells (cilia) attached to it which poke up from a third canal called the organ of Corti.
Organ of Corti transforms the stimulated hair cells into nerve impulses
Waveforms travelling down the basilar membrane peak in amplitude at differing spots along the way according to their frequency
Higher frequencies peak out at a shorter distance down the tube than lower frequencies
The hair cells at that peak point give a sense of that particular frequency
The distance between pitches follows the same logarithmic distance as our perception of pitch i.e. the placement of octaves are equidistant.
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