Chapter 6 - Hearing, Balance, Taste, and Smell

• decibel


  a measure of sound intensity, perceived as loudness
• hertz


  Cycles per second, as of an auditory stimulus; measure of frequency
• transduction


  the conversion of one form of energy to another
• pure tone


  a tone with a single frequency of vibration
• amplitude


  aka intensity. The force that sound exerts per unit area, experienced as loudness
• frequency


  the number of cycles per second in a sound wave, measured in hertz
• fundamental


  the predominant frequency of an auditory tone
• harmonic


  a multiple of the fundamental (frequency)
• timbre


  the characteristic sound quality of a musical instrument, as determined by the relative intensities of its various harmonics
• pinna


  the external part of the ear
• ear canal


  aka auditory canal; the tube leading from the pinna to the tympanic membrane
• inner ear


  the cochlea and vestibular apparatus
• middle ear


  the cavity between the tympanic membrane and the cochlea
• tympanic membrane


  aka eardrum; the partition between the external ear and the middle ear
• ossicles


  three small bones (incus, malleus, and stapes) that transmit vibration across the middle ear, from the tympanic membrane to the oval window
• oval window


  the opening from the middle ear to the inner ear
• cochlea


  a snail-shaped structure in the inner ear canal that contains the primary receptor cells for hearing
• scala vestibuli


  aka vestibular canal; one of the principal canals running along the length of the cochlea
• scala media


  aka middle canal; the central off the three spiraling canals inside the cochlea. situated between the vestibular canal and the tympanic canal
• scala tympani


  aka tympanic canal; one three principal canals running along the length of the cochlea
• organ of Corti


  a structure in the inner ear that lies on the basilar membrane of the cochlea and contains the hair cells and terminations of the auditory nerve
• hair cell


  one of the receptor cells for hearing in the cochlea, named for the stereocilia that protrude from the top of the cell and transduce vibrational energy in the cochlea into neural activity
• basilar membrane


  a membrane in the cochlea that contains the principal structures involved in auditory transduction
• tectorial membrane


  a gelatinous membrane located atop the organ of Corti
• stereocilium


  a tiny bristle that protrudes from a hair cell in the auditory or vestibular system
• inner hair cell


  one of the two types of receptor cells for hearing in the cochlea; positioned closer to the central axis of the coiled cochlea
• outer hair cell


  one of the two types of receptor cells for hearing in the cochlea; positioned farther from the central axis of the coiled cochlea
• vestibulocochlear nerve


  Cranial nerve VIII, which runs from the cochlea to the brainstem auditory nuclei
• cochlear nuclei


  brainstem nuclei that receive input form auditory hair cells and send output to the superior olivary nuclei
• superior olivary nuclei


  brainstem nuclei that receive input from both right and left cochlear nuclei and provide the first binaural analysis of auditory information
• inferior colliculi


  paired gray matter structures of the dorsal midbrain that process auditory information
• medial geniculate nucleus


  either of two nuclei (left and right) in the thalamus that receive input from the inferior colliculi and send output to the auditory cortex
• tonotopic organization


  the organization of auditory neurons according to an orderly map of the stimulus frequency, from low to high
• primary auditory cortex


  aka A1. the cortical region, located on the superior surface of the temporal lobe, that processes complex sounds transmitted from lower auditory pathways
• place coding theory


  theory that the pitch of a sound is determined by the location of activated hair cells along the length of the basilar membrane
• temporal coding theory


  theory that the pitch of the sound is determined by the rate of firing of auditory neurons
• infrasound


  very low frequency sound, generally below the 20 Hz threshold for human hearing
• ultrasound


  very high frequency sound, generally beyond 20,000 Hz, which is the upper bound for a young adult human
• interaural intensity difference


  a perceived difference in loudness between the two ears, which the nervous system can use to localize a sound source
• interaural temporal difference


  a difference between the two ears in the arrival of a sound, which the nervous system can use to localize a sound