Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
51 Cards in this Set
- Front
- Back
|
Hearing Frequencies |
capable of hearing 20-20,000 Hz at birth as you age, lose ability to hear very high and very low outer ear provides most gain for frequencies between 2kHz- 5 kHz |
|
|
Pinna |
outer ear captures sounds and directs it to the middle ear made of fibrocartilage attached to temporal bone by extrinsic muscles concha, helix, antihelix, tragus, antitragus and ear lobe (CHATAL) |
|
|
external auditory meatus |
ear canal an oval, s-shaped tube outermost is cartilage, continuous with the cartilage of the pinna along with pinna, frequency selective because of shape, 45 degrees |
|
|
Tympanic Membrane |
Middle ear (eardrum) vibrates in response to acoustic energy cone of light, annulus 3 layers: outer: thin layer continuous with the lining of the EAM middle: fibrous layer internal: continuous with the lining of the middle ear cavity |
|
|
Annulus |
thickened outer ring on tympanic membrane attached to a groove in the tympanic cavity |
|
|
Tympanic Cavity |
Middle ear where ossicles sit (malleus, incus, stapes) air filled cavity within the petrous portion of the temporal bone epitympanic recess: superior to the tympanic membrane, contains head of malleus and most of incus |
|
|
Tympanic Cavity Landmarks |
Superior wall: Tegmentum Inferior wall: Jugular Lateral wall: Membranous Medial wall: Labyrinthine Anterior wall: Carotid Posterior wall: Mastoid |
|
|
Ossicle |
within tympanic cavity transmits acoustic vibration from the TM to the inner ear 1. Malleus: largest, most lateral, suspended in the TC by 3 ligaments 2. incus: articulates laterally with the malleus and medially with the stapes, suspended by posterior ligament 3. stapes: smallest, footplate attached to the oval window |
|
|
Middle Ear Muscles |
Tensor Tympani Stapedial Muscle Actions: increases the stiffness of the ossicular chain, may provide some sound protectoin against low-frequency, intense sounds |
|
|
Tensor Tympani |
middle ear muscle located along and above the eustachian tube enters the TC attached to the manubrium of the malleus innervated by the branch of the mandibular nerve of the trigeminal |
|
|
Stapedial Muscle |
Middle ear muscle- stapedius smallest muscle in the body emerges from pyramid and inserts on the neck of the stapes innervated by the stapedial branch of the facial nerve |
|
|
Eustachian (Auditory) Tube |
extends downwards, medially and forward from the tympanic cavity to the nasopharynx normally closed to protect ear from pathogens opens during swallowing and yawning equalized pressure between the middle ear and external atmospheric pressure |
|
|
Transduction |
transforming one form of energy into another form of energy |
|
|
Acoustic energy changes to mechanical energy at what point? |
Tympanic membrane |
|
|
Impedance |
Obstruction mismatch: air filled middle ear space and fluid filled ear space sound going from air filled space to fluid filled: some is lost, sound becomes dampened ossicles help move sound |
|
|
Von Bekesy's Experiments |
observed basilar membrane motion in human cadavers (dead), found broad tuning |
|
|
traveling wave |
always at base of cochlea and moves up, base to apex, base is narrower amplitude changes as it moves along the length of the cochlea the position along the basilar membrane at which its amplitude is highest depends on the frequency of the stimulus |
|
|
Tuning Curve |
sharp tuning curve: want this to be able to distinguish one frequency from another 200 Hz: Hz before, needs more intensity and Hz after need more intensity, 200 needs less broad tuning: very loud sounds, death death of cells leads to poor frequency tuning of basilar membrane |
|
|
Outer vs.Inner hair cells |
outer: test tube shape inner: tear drop shape damage to outer hair cells lead to broad tuning |
|
|
Active Mechanism |
flow of energy enhances active mechanism 1. outer hair cell motivity: changes in length when different voltages applie 2. tip links |
|
|
inner ear |
2 labyrinthine systems osseous outer labyrinth (bony) membranous labyrinth (within bony labyrinth) |
|
|
Osseous Labyrinth |
composed of a series of ducts and cavities within the petrous portion of the temporal bone contains: vestibuli (sits between cochlea and semicircular canals) , semicircular canals, coiled cochlea |
|
|
Semicircular Canals |
lateral-most portion of the bony labyrinth superior, posterior, lateral canals involved in balance and body orientation |
|
|
coiled cochlea |
medial-most portion of bony labyrinth oval window is entrance coiled around central core: modiolus 2 3/4 turn from base to apex |
|
|
Membranous Cochlear Labyrinth |
spiral-shaped 3 canals: 1. scala vestibuli: contains perilymph 2. scala media: lies between the scala vestibuli and scala tympani, contain the organ of court (endolymph fluid fills area) 3. scala tympani: contains perilymph |
|
|
Reissner's Membrane |
top extends for the osseous spiral lamina to the outer bony wall joins the basilar membrane at the helicotrema at the apex of the cochlea divides scala vestibuli from the scala media |
|
|
Basilar Membrane |
bottom helps discriminate among very soft sounds formed at the osseous spiral lamina and extends out to the outer wall of the cochlea via the spiral ligament divides the scala media from the scala tympani |
|
|
Organ of Corti |
in scala media, sits on top of basilar membrane 1. inner hair cells 2. outer hair cells 3. tectorial membrane 4. supporting cells |
|
|
Inner hair cells |
one row approx. 3500 cells stereocilia sits on top |
|
|
outer hair cells |
3 rows approx. 12000 cells stereocilia sits on top ` |
|
|
tectorial membrane |
sits over hair cells gelatinous-like structure, tips of tallest rows of OHC come in contact |
|
|
Recticular Lamina |
holds the supporting cell in place at the top tissue in-between hair cells and under stereocilia |
|
|
What happens with the mechanical energy from the footplate of the stapes |
it gets transduced into electrical energy at the organ of corti high frequency sounds at base, low frequency sounds at apex middle ear: mechanical energy inner ear: electrical energy |
|
|
Afferent Innervation |
cochlea to brainstem(central nervous system) 30,000 neurons innervate the cochlea part of auditory nerve (8) that convey info from the cochlea to the central auditory system neural fibers branch off the hair cells and then travel to the spiral ganglion cells in the modiolous (very middle of cochlea) long neural process from the cell body in the ganglion then travel to the cochlear nucleus |
|
|
2 types of neural afferent fibers |
inner radial (type 1) fibers: represent 90-95% of all afferent fibers, innervate inner hair cells (many fibers attached to one inner hair cell) outer spiral fiber (type 2): synapse on multiple outer hair fibers, one to many innervation (one fiber to many fibers) |
|
|
Efferent Auditory Pathway |
brainstem to cochlea from auditory neural pathway to hair cells may enhance fine frequency tuning in the cochlea not much known |
|
|
Resting Potential |
a neuron is not sending a signal inside of the neuron is negative relative to the outside (-70mV) higher concentration of Na+ located outside the cell compared to K+ inside the cell = inside negative at rest= more negative inside= potassium outside= sodium |
|
|
Depolarization |
sodium ions moving into axons, inside becoming more positive loss of positive ions from the outside of the cell inside becomes positive Na+ ions move into the cell signal/ impulse is transmitted |
|
|
Repolarization |
once a specific positive charge is within the cell the positive ions (Na+) are moving outside the cell (reversal) inside becoming more negative |
|
|
Refactory Period |
during repolarization pause, flushing a toilet absolute: cell cannot receive another neural impulse Relative: call has repolarized sufficiently such that a strong neural impulse can lead to excitation |
|
|
response to auditory nerve fibers |
auditory nerve responds to input from hair cells depolarizatoin --> neurotransmitter release --> AP in auditory nerve fibers |
|
|
which neural fibers are connected? |
inner radial outer spiral |
|
|
what info is the auditory nerve getting? |
frequency, intensity, temporal (time)
|
|
|
Spontaneous Activity |
neurons produce action potentials at random intervals without stimulation when stimulus ends, regular activity begins |
|
|
Tuning Curves |
representations of how specific auditory neurons respond to different frequencies lowest point= characteristic frequency have steep high-frequency slope extended low- frequency tail narrow tip |
|
|
Rate- level functions |
representations of how an auditory nerve fiber response changes with changing stimulus level (intensity) input/output functions |
|
|
Histograms |
representations of the response of auditory neurons over time (temporal) don't necessarily get a response each time present a stimulus but you will get a pattern with repeated trials pattern is plotted on PST histogram plot showing number of spikes as function of time after stimulus presented |
|
|
phase locking |
auditory nerve responses "trace out" the time waveform of sound only positive parts of time waveform are represented signals up to 5000 Hz- best at 1000Hz |
|
|
frequency coding |
place= tuning cuves, along basilar membrane, higher frequencies- base, lower- apex time= histograms wide on graph= high level time takes for 1 cycle= period cochlea performs frequency analysis, see results in auditory nerve firing patterns auditory nerve response is consisten with cochlear response |
|
|
intensity coding |
discriminate between 0 and 140 dB SPL ratio of pressure changes is 10,000,000:1 spread of excitation along the basilar membrane may also be used to code intensity |
|
|
dynamic range |
point of increase, highest minus lowest individual auditory nerve fibers cannot provide a code for intensity across the dynamic range of hearing |
