Hearing Flashcards
Pure Tone
Simple sinusoidal wave. Our voices and music and shit are not
2 Parameters of Sound
Frequency - pitch Pressure Level (decibels) loudness intensity
Auditory Field
About 20 to 20k Hz, but conversation area greatly increased from like 300 to 3k Hz
3 Functions of Outer Ear
Collect sound waves
Amplify sound pressure level
Frequency filter for localization of sound elevation
Sound Force Amplification by ME
Pressure = F/SA and TM to oval window is 20:1 so it decreases SA. Lever effect of ossicular chain
5 Differences b/w IHC and OHCs
Calix shaped, close to spiral ganglion, single row, afferent, 10 type 1 neurons synapse vs. columnar, far, 3 rows, contract for frequency tuning, and have 1 type II neurons connecting about 10
2 Turns/Pitch Distribution
Apical turn for low freq/pitch sounds and basal turn for high
Rapid Succession Mech
Calcium influx triggers motor prot which drives down tip link, reducing time constant of K channel opening, repolarizing the cell, and thus allowing cycles of mechanotransduction to occur in rapid succession (high freqs)
Passive Tonotopy
Tonal separation dependent on physical properties of cochlea, where high freqs vibrate base and low vibrate apex where its less stiff
Active Tonotopy
Finer mech via OHCs contracting at their very specific range, causing a 50 dB increase
Frequency Preservation in Auditory Nerve
Bc auditory nerve fibers connect w/ IHC in approx 1:1 ratio, each auditory nerve fiber transmits information about only small part of audible freq spectrum. So apical nerves respond low freqs and etc
2 Central Auditory Pathways
Primary: messages from cochlea
Non-primary: all types of sensory messages (reticular)
Otoacoustic Emissions
Normal low level sounds produced by ear as part of hearing process. Can be reduced or absent in cases of certain types of hearing loss. Reflect activity of OHCs, most sensitive cells of organ of Corti so can be objective screening test in newborns (who can’t directly be tested) or adults at risk of hearing loss like workers
Brainstem Auditory Evoked Potentials
See it going through auditory pathway (I. auditory n. II. cochlear nuclei III. Sup olive IV. lateral lemniscus V. Inf colliculus) and see if there’s any latency at the points indicating a problem. Additional tests for children/babies
Bone-Air Gap
Means bone conduction is better than air, so there’s some sort of conductive hearing loss
4 Treatments for OME
Antibiotics
Tympanostomy tubes
Adenoidectomy
Treatment for Otosclerosis
Stapedectomy and replace w/ proper functioning synthetic one
2 Treatments for Congenital Ear Canal Atresia
Atresia repair
Bone Anchored Hearing Aids (BAHA) - metal screw directly into bone and vibration goes to cochlea
Aminoglycoside Ototoxicity (3)
Dose dependent damage to hair cells, can have genetic predisposition (often through mtDNA). Starts at cells w/ greater energy requirements (high freq) and progresses from OHCs to IHCs, base to apex
Speech Audiogram w/ OHC Damage
Need 50 dB to just start picking up any sound, and never get 100% bc missing cells to tune to those words
Cochlear Implant
Electrodes that process sound turn sound into electrical signals and placed inside cochlea at same tonotopic distribution
2 Kinds of Noise Induced Hearing Loss
Temporary Threshold Shift (TTS)
Permanent (PTS)
Sign of NILH on Pure Tone Audiometry Test
Backwards check mark at end
Socio-acusis
Leisure noise exposure
Presbycusis
Hearing of loss from age, hair cells damaged first then nerve fibers. High pitch goes first.
Connexin 26
AR nonsyndromic, most comon cause of genetic hearing loss in children
