Auditory Function Flashcards
What is the pitch of a sound determined by?
Frequency
Humans have a range of 20-20,000 Hz
What is the tone of a sound determined by?
The shape of the waveform
Sine waves = pure tones
Complex waveforms with regular patterns = musical
Irregular waveforms = noise
What is the loudness of a sound determined by?
Amplitude
What are the functions of the outer ear?
Amplification - funnel and resonator
Localization - of sounds differing in vertical elevation
What is conduction deafness and some potential causes?
Obstructions in the auditory canal decreasing sound conduction to the middle ear
Cold due to excess mucus accumulation, otitis media, damage to ossicles, abnormal tissue growth
What is impedance matching?
The fluid of the inner ear has a greater impedance to motion than air
The surface area difference between the tympanic membrane and the oval window concentrates the force
The ossicles (bones) of the middle ear larger amplitude, lower force vibrations into smaller amplitude, higher force vibrations of the fluid of the inner ear
What is the attenuation reflex?
The tensor tympani and stapedius attach to the ossicles.
Loud sounds cause these muscles to contract, increasing the rigidity of the ossicles and reducing sound conduction to the middle ear
How are fluid waves generated and what is their affect?
The Stapes transfers air pressure waves to the oval window
The inward movement of the oval window pushes the incompressible perilymph, resulting in downward movement of Reissner’s membrane.
This causes downward movement of the endolymph, and subsequently, the basilar membrane
Describe the non-uniform structure of the basilar membrane and its significance
It is narrower and stiffer at the base, near the oval and round windows, and it is wider and looser at the apex
The allows the basilar membrane to be tuned so that different locations along the membrane vibrate maximally at specific frequencies
How are the hair cells in the cochlea stimulated?
The basilar membrane and tectorial membrane pivot along different axes, therefore upward and downward movments of these membranes create alternating shear forces on the cilia, bending them in alternating directions
What is the tectorial membrane?
Membrane overlying the hair cells in the basilar membrane that contacts the stereocilia
Describe afferent nerve firing during hair cell transduction.
The alternating bending of stereocilia creates alternating depolarization and hyperpolarization of the hair cell membrane
This creates corresponding increase and decrease in transmitter release and afferent firing
What is nerve deafness?
Sensorineural hearing loss that results from damage to the cochlear hair cells or afferent nerve fibers
Pressure waves cannot be transduced into electrical nerve activity
What are some causes of nerve deafness?
Prenatal exposure to rubella, influenza and mumps
Environmental toxins (methyl mercury)
Ototoxic drugs
Exposure to loud noises
What is Prebycusis?
Progressive loss of hearing with aging
