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45 Cards in this Set

  • Front
  • Back
What are the two parts of the outer ear?
Pinna and ear canal
What does the pinna do?
-captures sound, focuses and enhances sound in speech range (2k-5k Hz)
What is the purpose of the middle ear?
concentrates sound energy and transmits it from external environment to cochlea
What are the parts of the middle ear?
a. Tympanic membrane
b. Ossicles: malleus, incus, stapes (or hammer, anvil, stirrup)
c. Oval window
d. Regulation of vibration intensity: tensor tympani and stapedius
What are the parts of the inner ear?
a. Cochlea--three canals: tympanic, vestibular, middle
b. Round window to relieve pressure on incompressible fluid filling these canals
c. Basilar membrane
d. Organ of Corti
What are the names of the three ossicles?
malleus, incus, stapes
What parts of the middle ear are responsible for regulating vibration intensity?
tensor tympani and stapedius
What are the three canals of the cochlea?
tympanic, vestibular, middle
What is the round window used for?
relieve pressure on incompressible fluid filling these canals
What is the basilar membrane used for?
vibrates at different places for different frequencies
What is the organ of coti?
Sound transducer
How does the organ of coti work?
1) Basilar membrane vibrates
2) Inner hair cells and outer hair cells (about 12000 total) extend stereocilia into indentations in tectorial membrane and move when basilar membrane vibrates
3) Tip links on stereocilia open K+ gates, which depolarize cells cause influx of Ca+2 at base of cell 4. Most sound information carried by inner hair cells
5. Outer hair cells modulate and "tune" response of inner hair cells by changing distance of tectorial membrane from tip of IHC's --longer when hyperpolarized
—shorter when depolarized
--effect is to amplify or dampen basilar membrane motion
How does the ear analyze incoming sounds?
1. Sound waves cause waves in cochlear fluid
2. Shape and thickness of basilar membrane performs a physical Fourier analysis
3. Tuning curves of individual auditory nerve cells
What are sources of sounds emitted by the ear?
Evoked Otoacoustic emissions—triggered by external stimulation and seem to be part of normal sharpening of sound perception by cochlea itself

Spontaneous otoacoustic emissions--not perceived by the person, but are associated with more sensitive hearing
What is the path from the ear to the brain?
1. Inner and some outer hair cells synapse on cells of auditory nerve
2. Auditory nerve branches, goes to dorsal and ventral cochlear nuclei.
3. Several paths from cochlear nuclei:
--one set to superior olivary nuclei—from both ears--first binaural interaction
--other sets to inferior colliculi, then to medial geniculate nucleus of thalamus
4. Then to primary auditory cortex
5. And other auditory analysis systems for complex sounds or speech
What are the theories of pitch discrimination?
Place Theory
Volley Theory
What is Place theory in terms of pitch discrimination?
perception depends on where on the basilar membrane the maximal displacement occurs
What is Volley theory in terms of pitch discrimination?
perception depends on frequency and pattern of neural firing (phase locking)
What is the real story of pitch discrimination?
Place Theory above 1.5 kHz; Volley Theorymostly below 1.5 kHz, but up to 4kHz
What are ways we localize sound?
1. Monaural detection: loudness of sound
2. Binaural detection
How do we localize sounds using both ears?
a. Intensity differences for high frequency sounds
b. Latency differences (onset and phase disparity) for low-frequency sounds
c. As before, it's really duplex (both)
d. Most done in the superior olivary nucleus
e. And some spectral filtering by the pinna
How / Where do we perceive complex sounds?
1. Dorsal stream (parietal lobe): spatial location="where"
2. Ventral stream (temporal lobe): complex analysis="what"
3. Musical training enlarges Heschl's gyrus
What are the three types of deafness
1. Conduction deafness
2. Sensorineural deafness
3. Central deafness
Define Conduction deafness
problem is in the outer or middle ear, so sound never reaches the cochlea
Define Sensorineural deafness
problem is in the cochlea or the auditory nerve fibers (too much rock music)
Define Central deafness
problem is in the cortex, in comprehending sound; examples: word deafness, cortical deafness (loss of projections from medial geniculate--get reflexes and body responses, but no experience of hearing)
What does the Vestibular sense do?
motion/acceleration detection
How does the vestibular sense work?
1. Semicircular canals, oriented at right angles, filled with fluid
2. Connected by utricle to the saccule
3. Ampullae at junction between canal and utricle contain hair cells with cilia embedded in a gelatinous layer called the cupula; otoliths increase sensitivity.
4. Acceleration in any direction causes hair cells to bend and start a generator potential.
5. Receptors in utricle and saccule respond to static position of head
What are the brain pathways for the vestibular sense?
1. Fibers from receptors synapse in vestibular nuclei, while another set go to the cerebellum
2. Pathway complicated from there--to motor nuclei of eye muscles, thalamus and cortex
What is the theory of Motion Sickness?
1. Sensory conflict theory
What are the two taste receptor cell types?
a. Papillae
b. Taste buds
Describe papillae
fungiform around top edge (one taste bud per), foliate on sides of back, circumvallate on top of back of tongue
Describe taste buds
multiple receptor cells in various stages of development
What are the five basic tastes?
What are the details of the salty taste?
chemical salts, usually Na+ going through Na+ channels
What are the details of the sour taste?
chemical acids, i.e., H+ ions present -H+ blocks K+ channels so ion cannot get out
What are the details of the sweet taste?
saccharides, but that is not all
--second messenger G proteins: gustducins —coupled T1R2 +T1R3 receptors
What are the details of the bitter taste?
many different types
--Also gustducin second messengers
--25 types of T2R receptors, so pattern is the key
What are the details of the umami taste?
—"meaty" taste
--glutamate receptors
--amino acid receptors: T1R1+T1R3
What are the pathways for taste?
Initially to medulla, then to posterior medial nucleus of thalamus, then to somatosensory cortex
What is the physiology of the olfactory sense?
a. Olfactory epithelium with receptors, supporting cells and basal cells that will become receptor cells
b. Apical dendrite of receptor cells ends in a dendritic knob with cilia embedded in mucosal layer of epithelium
c. Connections to olfactory bulb are in glomeruli
d. Turbinates direct airflow to the receptor areas
How is olfactory transduction accomplished?
Transduction is another second messenger/G protein exercise
--Each odor seems to have its own receptor type, but all seem to use same Golf protein
How many genes are involved in olfactory senses?
Mice have 1000 different receptor proteins, humans have 900 genes but only 350 are expressed
What are the olfactory pathways to the brain?
a. Axons of olfactory receptors are very small and unmyelinated; pass through cribiform plate to synapse on mitral cells in olfactory bulb
b. One path goes through amygdala to hypothalamus, then to orbitofrontal cortex
c. Another path goes through prepyriform cortex (on tip of temporal lobe near amygdala), then to medial dorsal thalamus then orbitofrontal cortex
4. Note unique aspect: both pathways reach cortex without synapsing in thalamus; and both pass through limbic system on the way there.
What is the Vomeronasal system
specialized for pheromones
--human system is vestigial, and genes that encode the receptors are nonfunctional (but something works at least a little in humans)