Auditory System Structure and Processing (6A) - Psych & Soc

What is the function of the round window in cochlear mechanics?

Pressure release membrane that permits fluid displacement. Allows cochlear fluid to move as oval window pushes inward.
What fluid fills the scala media (cochlear duct)?

Endolymph. High-potassium fluid creates voltage gradient for hair cell function.
What is the immediate mechanical event that opens hair-cell transduction channels?

Deflection of stereocilia (shearing against the tectorial membrane). Tip links pull channels open when stereocilia bend.
Which cue is primarily used to localize low-frequency sounds: ITD or ILD?

ITD (interaural time difference). Low frequencies wrap around head, preserving timing differences.
Identify the primary auditory cortex location in the brain.

Temporal lobe (Heschl gyrus; superior temporal gyrus). Located in the transverse temporal gyrus (Brodmann areas 41/42).
Which part of the basilar membrane responds best to low-frequency sounds?

Apex of the cochlea (near the helicotrema). Wide, flexible apex vibrates best with low-frequency sounds.
What is the main role of the ossicles in auditory transduction?

Amplify and transmit vibrations to the oval window. The lever action increases force to overcome fluid resistance.
What is the name of the nerve that carries auditory information from the cochlea to the brain?

Cochlear nerve (part of CN VIII, vestibulocochlear nerve). Auditory division of cranial nerve VIII carries sound information.
What thalamic nucleus relays auditory information to the primary auditory cortex?

Medial geniculate nucleus (medial geniculate body). Thalamic relay between midbrain and cortex.
What is the basilar membrane's key role in frequency discrimination?

Different locations resonate to different sound frequencies (tonotopy). Creates a frequency map along the cochlea's length.
What is the correct sequence of structures that sound waves pass through in the outer ear?

Pinna (auricle) auditory canal tympanic membrane. Sound travels from outside to eardrum through these structures.
Which inner ear structure is directly displaced by the stapes at the oval window?

Perilymph in the scala vestibuli of the cochlea. Stapes footplate pushes oval window, creating fluid waves.
What is the cochlea and what does it do in auditory transduction?

Fluid-filled spiral that converts vibrations into neural signals. Shaped like a snail shell with three fluid-filled chambers.
Identify the key brainstem relay nucleus that receives the first synapse from the auditory nerve.

Cochlear nucleus. First central synapse in the auditory pathway at the medulla.
What is the primary coding strategy for sound intensity (loudness) at the auditory nerve?

Increased firing rate and recruitment of more auditory nerve fibers. Louder sounds cause greater hair cell deflection and neural activity.
Which structure carries auditory information from the cochlea to the brainstem?

Cochlear nerve (auditory branch of cranial nerve VIII). Part of the vestibulocochlear nerve carrying auditory signals.
What brainstem nucleus is the first major relay for cochlear nerve input?

Cochlear nucleus. First central processing station in the medulla.
What is the correct order of sound transmission from outer ear to inner ear structures?

Pinna → ear canal → tympanic membrane → ossicles → oval window → cochlea. Sound waves travel through air-filled structures to fluid-filled cochlea.
What is the correct order of sound conduction structures from outer ear to cochlea?

Pinna → ear canal → tympanic membrane → ossicles → oval window → cochlea. Sound travels through outer, middle, then inner ear structures sequentially.
What is the primary neurotransmitter released by cochlear hair cells onto auditory nerve fibers?

Glutamate. Excitatory neurotransmitter activates spiral ganglion neurons.
What is the primary auditory cortex location in the brain?

Heschl gyrus in the superior temporal lobe. Also called transverse temporal gyrus or Brodmann area 41.
What structure contains the hair cells responsible for auditory transduction?

Organ of Corti (within the cochlear duct). Contains inner and outer hair cells on the basilar membrane.
Where is the primary auditory cortex located?

Superior temporal gyrus (temporal lobe). Heschl's gyrus in the superior temporal lobe.
What structure contains the hair cells that transduce sound in the cochlea?

Organ of Corti. Sits on basilar membrane and contains sensory hair cells.
What is the primary function of the ossicles in hearing?

Amplify and transmit vibrations from tympanic membrane to oval window. The ossicles form a lever system that increases force to overcome the impedance mismatch between air and cochlear fluid.
What is the correct order of sound transmission from outer ear to inner ear fluids?

Pinna → canal → tympanic membrane → ossicles → oval window → cochlea. Sound travels through outer, middle, then inner ear structures sequentially.
What is the key ionic basis for cochlear hair-cell depolarization?

K $^+$ influx from endolymph through mechanically gated channels. Endolymph's high $K^+$ concentration drives depolarization when channels open.
What is the function of the Eustachian tube in the middle ear?

Equalizes middle-ear pressure with atmospheric pressure. Prevents barotrauma and maintains ossicle mobility.
What is the organ of Corti?

Sensory epithelium containing hair cells on the basilar membrane. Contains inner and outer hair cells that detect sound vibrations.
Which cochlear region responds best to low-frequency sounds: base (near oval window) or apex?

Apex. The wide, flexible apex vibrates best with low frequencies.
What is the function of the pinna (auricle) in auditory processing?

Funnels sound waves into the external auditory canal. The pinna's shape collects and directs sound waves toward the ear canal to enhance auditory reception.
Which region of the basilar membrane responds best to high-frequency sounds?

Base (near the oval window). The stiff, narrow base vibrates best with high frequencies.
What is the immediate stimulus that opens mechanically gated channels in cochlear hair cells?

Deflection of stereocilia from basilar membrane vibration. Bending opens ion channels, depolarizing the hair cells.
What is tonotopic organization in the cochlea?

Different sound frequencies peak at different basilar membrane locations. Frequency-to-place mapping along the basilar membrane.
What is the function of the Eustachian tube in the auditory system?

Equalizes air pressure across the tympanic membrane. Connects middle ear to throat for pressure balance.
Which cue primarily supports sound localization in the horizontal plane for low frequencies?

Interaural time difference (ITD). Sound reaches ears at slightly different times.
What is the role of the basilar membrane in pitch discrimination?

Place coding via tonotopic vibration along its length. Different frequencies cause peak vibration at different membrane locations.
What is the main function of the superior olivary complex in auditory processing?

Sound localization using binaural timing and intensity cues. Compares inputs from both ears to determine sound direction.
Identify the membrane that hair cell stereocilia contact during cochlear vibration.

Tectorial membrane. Shearing between this and basilar membrane bends stereocilia.
Where is primary auditory cortex located anatomically?

Superior temporal gyrus (Heschl gyrus) in the temporal lobe. Also called A1; processes basic sound features.
Which three bones form the ossicles of the middle ear, in order from lateral to medial?

Malleus → incus → stapes. These tiny bones form a mechanical chain from eardrum to inner ear.
What is the medial geniculate nucleus, and what modality does it relay?

Thalamic relay nucleus for auditory information to cortex. All auditory information passes through this thalamic nucleus.
What is the primary function of the tympanic membrane in auditory transduction?

Vibrates in response to sound and drives ossicle movement. Converts sound waves to mechanical vibrations for the ossicles.
What is the function of the pinna (auricle) in hearing?

Collects and funnels sound into the auditory canal. Acts as a natural amplifier directing waves toward the ear canal.
What is the main role of the ossicles in auditory processing?

Amplify and transmit vibrations to the oval window. Lever action increases force by ~20x to overcome fluid resistance.
What is the specific sensory receptor cell type for hearing in the cochlea?

Hair cells. Mechanoreceptors that convert mechanical deflection to electrical signals.
What is the difference between place theory and frequency theory of pitch perception?

Place: location on basilar membrane; Frequency: firing rate matches sound frequency. Place uses spatial coding; frequency uses temporal coding of pitch.
Which cue is primarily used for sound localization by interaural level differences (ILD)?

High-frequency sounds (head shadow effect). Intensity differences from head blocking help localize high frequencies.
What is the thalamic relay nucleus for auditory information before cortex?

Medial geniculate nucleus (MGN) of the thalamus. All sensory info (except smell) relays through thalamus.
Identify which cochlear region encodes high-frequency sounds in place theory.

Base of the cochlea (near the oval window). Stiff basilar membrane vibrates best at high frequencies.
Identify the auditory cue primarily used to localize sounds in the horizontal plane.

Interaural time and interaural intensity (level) differences. Brain compares timing and loudness differences between ears.
Which part of the basilar membrane responds best to low-frequency sounds?

Apex of the cochlea (near the helicotrema). Wide, flexible membrane vibrates best at low frequencies.
Which cochlear structure contains the sensory hair cells for hearing?

Organ of Corti. Contains inner and outer hair cells that transduce sound.
What is the auditory nerve, anatomically, and what does it carry?

Cochlear branch of CN VIII; carries auditory afferent signals. Part of vestibulocochlear nerve that transmits sound signals to brain.
What is the immediate electrical result of mechanically opening hair-cell channels?

Hair-cell depolarization and increased neurotransmitter release. K+ influx depolarizes cells, triggering glutamate release.
What are the three middle ear ossicles in correct order from tympanic membrane to oval window?

Malleus → incus → stapes. Named from Latin: hammer, anvil, stirrup based on their shapes.
Identify the correct ascending auditory pathway from brainstem to cortex after CN VIII synapses in the cochlear nucleus.

Cochlear nucleus $ $ superior olive $ $ inferior colliculus $ $ MGN $ $ auditory cortex. Bilateral pathway with crossings at multiple brainstem levels.
Which cochlear region responds best to low-frequency sounds?

Apex of the cochlea (near helicotrema). Basilar membrane is flexible at apex, responding to low frequencies.
What is the main role of the ossicles in hearing?

Amplify and transmit vibrations to the oval window. Ossicles provide mechanical advantage to overcome fluid impedance.
Which cue is primarily used to localize high-frequency sounds: ITD or ILD?

ILD (interaural level difference). Head shadow creates intensity differences for high frequencies.
What is the function of the tympanic membrane (eardrum)?

Vibrates in response to sound; converts air waves to mechanical motion. Thin membrane that initiates mechanical transduction of sound.
What is the round window, and what is its key role in cochlear mechanics?

Pressure-release membrane that permits cochlear fluid displacement. This flexible membrane bulges outward to accommodate fluid shifts, preventing pressure buildup during sound transmission.
What neurotransmitter is released by cochlear hair cells onto auditory nerve fibers?

Glutamate. The excitatory neurotransmitter at hair cell-nerve synapses.
Which three middle-ear bones (ossicles) transmit vibrations to the inner ear?

Malleus, incus, stapes. These tiny bones amplify and transmit vibrations from eardrum to inner ear.
What is the cochlea, and what type of transduction occurs there?

Spiral inner-ear organ; mechanical vibrations transduced to neural signals. The cochlea's coiled structure houses fluid and membranes that facilitate the conversion of mechanical energy to electrical impulses.
What is the specific role of the stapes at the oval window?

Transmits ossicle vibrations into cochlear fluid via the oval window. The footplate pushes fluid in the cochlea, converting mechanical to fluid waves.
What is the primary role of the round window in the cochlea?

Pressure relief; allows cochlear fluid displacement. Must move opposite to oval window for fluid flow.
Which brainstem nucleus is the first major synapse for auditory nerve input?

Cochlear nucleus. Located in the medulla, it processes basic sound features.
What structure directly bends hair cell stereocilia during sound transduction?

Tectorial membrane (shearing against stereocilia). Relative motion between membranes bends stereocilia during vibration.
Which part of the basilar membrane responds best to high-frequency sounds?

Base of the cochlea (near the oval window). Stiff base resonates with high frequencies; flexible apex with low.
Identify the three ossicles of the middle ear in anatomical order from eardrum to oval window.

Malleus → incus → stapes. The hammer, anvil, and stirrup form the ossicular chain.
Which pitch theory best explains low-frequency sounds, and what is its core idea?

Frequency theory; auditory nerve firing rate tracks sound frequency. Neural firing synchronizes with low-frequency sound waves.
Which three bones make up the ossicles of the middle ear, in order from lateral to medial?

Malleus, incus, stapes. These tiny bones connect the eardrum to the inner ear.
Which structure is classically described as the first major brainstem relay for auditory input?

Cochlear nucleus. Receives direct input from spiral ganglion neurons.
What is the functional difference between the oval window and the round window?

Oval: input to cochlea; round: pressure release/compensation. Oval receives vibrations; round bulges out to accommodate fluid displacement.
What is tonotopic organization in the cochlea?

Specific basilar membrane locations respond to specific frequencies. Creates a frequency map along the cochlear length.
What is the function of the round window in the cochlea?

Pressure release; allows cochlear fluid displacement. Fluid must move somewhere when oval window pushes in.
What structure do cochlear hair cells sit on that vibrates tonotopically?

Basilar membrane. Its width and stiffness vary to create frequency selectivity.
Which part of the basilar membrane responds best to high-frequency sounds?

Base of the cochlea (near the oval window). Base is stiff and narrow, resonating with high frequencies.
What is the main role of the ossicles in auditory transduction?

Amplify and transmit vibrations to the oval window. Acts as an impedance-matching lever system.
Which midbrain structure is a major relay and reflex center for auditory information?

Inferior colliculus. Integrates bilateral input and mediates auditory reflexes.
What structure separates the outer ear from the middle ear?

Tympanic membrane (eardrum). This membrane vibrates when sound waves hit it, initiating the hearing process.
Which three bones form the ossicles of the middle ear?

Malleus, incus, stapes. These tiny bones form the ossicular chain in order from lateral to medial.
Which thalamic nucleus relays auditory information to the auditory cortex?

Medial geniculate nucleus (MGN). Final relay before auditory information reaches cortex.
What ion is primarily responsible for depolarizing cochlear hair cells when mechanosensitive channels open?

K $^+$ influx from potassium-rich endolymph. Endolymph has high $K^+$ concentration unlike typical extracellular fluid.
What is tonotopic organization in the cochlea?

Different sound frequencies peak at different basilar membrane locations. Creates a frequency map along the cochlea's length.
What is the first major brainstem nucleus that receives input from the auditory nerve?

Cochlear nucleus. It processes initial auditory input, extracting features like timing and intensity before relaying to higher centers.
What is the primary function of the pinna (auricle) in hearing?

Collects and localizes sound; funnels sound into the auditory canal. The outer ear structure helps determine sound direction and amplifies certain frequencies.
What is tonotopic organization in the cochlea?

Mapping of sound frequency to specific basilar membrane locations. Different frequencies peak at different basilar membrane positions.
Which brainstem nucleus is the first major synapse for auditory nerve fibers?

Cochlear nucleus. Located in medulla, it's where auditory nerve fibers first synapse.
Which part of the basilar membrane responds best to low-frequency sounds?

Apex (near the helicotrema). The apex is wider and more flexible, allowing it to vibrate maximally with slower waves of low frequencies.
What is the primary function of the tympanic membrane in auditory transduction?

Vibrates in response to sound and drives ossicle movement. Converts sound waves to mechanical vibrations for the ossicles.
What is the primary role of the round window in the cochlea?

Pressure release membrane that permits cochlear fluid displacement. Allows fluid movement when oval window pushes inward.
Which cochlear region responds best to high-frequency sounds?

Base of the cochlea (near oval window). Stiff basilar membrane vibrates to high frequencies.
What neurotransmitter is primarily released by inner hair cells onto the auditory nerve?

Glutamate. Excitatory neurotransmitter activates spiral ganglion neurons.
What is the basilar membrane, and what does it do during sound processing?

Vibrating cochlear membrane; performs frequency-based mechanical analysis. Its varying stiffness allows different sections to resonate at specific frequencies, enabling spectral decomposition of sound.
What are the three auditory ossicles in the correct anatomical order?

Malleus → incus → stapes. The hammer, anvil, and stirrup transmit vibrations sequentially.
Which cranial nerve carries auditory information from the cochlea to the brainstem?

Vestibulocochlear nerve (CN VIII), cochlear branch. The auditory division of the eighth cranial nerve.
What auditory coding mechanism primarily represents sound intensity (loudness)?

Rate coding and recruitment (more neurons active). Louder sounds cause faster firing rates and activate more neurons.
Which cortical area is the primary auditory cortex, and where is it located?

A1 in the superior temporal gyrus (temporal lobe). First cortical processing area for sound.
Which cochlear membranes bound the scala media (cochlear duct)?

Basilar membrane and Reissner (vestibular) membrane. These membranes separate the three fluid-filled cochlear chambers.
What is the oval window, and what role does it play in hearing?

Membrane where stapes transmits vibrations into cochlear fluid. Stapes footplate pushes here to create fluid waves.
What is the oval window, and what does it transmit?

Membrane where stapes transmits vibrations into cochlear fluid. Stapes footplate pushes here to create fluid waves in cochlea.
What is the immediate stimulus that bends cochlear stereocilia during sound transduction?

Shearing between tectorial membrane and basilar membrane. Relative motion deflects hair cell bundles.
What is the name of the nerve that carries auditory information from the cochlea to the brain?

Cochlear nerve (auditory branch of CN VIII). Part of vestibulocochlear nerve carrying auditory signals.
What is the immediate mechanical event that triggers hair-cell depolarization?

Stereocilia bending opens mechanically gated ion channels. Tip links pull channels open when stereocilia deflect.
What is the function of the oval window in the auditory system?

Transmits stapes vibrations into cochlear fluid. The stapes footplate pushes here to create fluid waves.
What is the tympanic membrane, and what does it do when sound arrives?

Eardrum; vibrates to convert air pressure waves into mechanical motion. It acts as a barrier that oscillates in response to sound pressure, initiating mechanical transmission in the middle ear.
Which binaural cue is most important for localizing low-frequency sounds?

Interaural time difference (ITD). Low frequencies have longer wavelengths, allowing phase differences between ears to indicate sound direction.
Which cochlear region (base or apex) is maximally displaced by high-frequency sounds?

Base (near the oval window). Basilar membrane is stiffer at base, resonating with high frequencies.
What is the function of the Eustachian tube in the auditory system?

Equalizes middle ear pressure with atmospheric pressure. Prevents pressure buildup that would dampen tympanic membrane movement.
What is the difference between sensorineural hearing loss and conductive hearing loss?

Sensorineural: hair cells/nerve; Conductive: outer or middle ear conduction. Sensorineural affects neural transduction; conductive blocks sound transmission.
What is the key distinction between place theory and frequency theory of pitch coding?

Place: location on basilar membrane; Frequency: firing rate matches sound frequency. Place uses spatial coding; frequency uses temporal coding.
Which option best distinguishes sensorineural hearing loss from conductive hearing loss?

Sensorineural: cochlea/CN VIII; Conductive: outer or middle ear. Sensorineural affects sensory cells; conductive affects sound transmission.
Which region of the basilar membrane responds best to low-frequency sounds?

Apex (near the helicotrema). The wide, flexible apex vibrates best with low frequencies.
What is the oval window, and what does it do?

Membrane where stapes pushes; transmits vibration into cochlear fluid. Interface between middle ear air and inner ear fluid.
What is the correct path of sound conduction from outer ear to cochlear receptors?

Pinna → ear canal → tympanic membrane → ossicles → oval window → cochlea. Sound travels through outer, middle, then inner ear structures sequentially.
Which cochlear region responds best to low-frequency sounds?

Apex of the cochlea. Flexible basilar membrane responds to low frequencies.
What are cochlear hair cells, and what is their essential function?

Mechanoreceptors that convert stereocilia bending into receptor potentials. These cells depolarize when fluid motion deflects their stereocilia, triggering neurotransmitter release to afferent nerves.
Which brainstem nucleus is the first major relay for auditory input from the cochlear nerve?

Cochlear nucleus. First stop in brainstem for all auditory signals.
What is the main function of the ossicles in the middle ear?

Amplify and transmit vibrations to the oval window. Ossicles act as mechanical amplifiers for sound.
What is the immediate mechanical stimulus that bends cochlear hair-cell stereocilia?

Shearing motion between basilar and tectorial membranes. Fluid waves cause differential membrane movement, bending hair cells.
What is the auditory nerve, and which cranial nerve number is it?

Cochlear branch of vestibulocochlear nerve, CN VIII. Carries auditory signals from cochlea to brainstem.
What is the first major brainstem relay nucleus for auditory input from CN VIII?

Cochlear nucleus. First central processing station for ascending auditory pathways.
Which cranial nerve carries auditory information from the cochlea to the brainstem?

Vestibulocochlear nerve (CN VIII). The auditory division of CN VIII transmits cochlear signals.
What mechanical event directly causes auditory hair-cell stereocilia to bend?

Relative motion of basilar membrane against tectorial membrane. Two membranes slide past each other during sound waves.
Which auditory nerve carries signals from the cochlea to the brainstem?

Cochlear nerve (part of cranial nerve VIII). Vestibulocochlear nerve's auditory division.
What is the immediate mechanical stimulus that bends stereocilia of cochlear hair cells?

Shearing between tectorial membrane and basilar membrane motion. Differential movement bends hair cell stereocilia.
What is the organ of Corti?

Sensory epithelium containing hair cells on the basilar membrane. Contains inner and outer hair cells that transduce sound to neural signals.
What is the organ of Corti?

Sensory epithelium containing hair cells on the basilar membrane. Contains inner and outer hair cells that transduce sound.
What is the main mechanical role of the ossicles in sound transmission?

Amplify vibrations and transmit them to the oval window. Acts as a lever system to increase force on the smaller oval window.
What is the immediate stimulus that causes inner hair cell depolarization in the cochlea?

Stereocilia deflection opens mechanically gated ion channels. Bending of hair cell projections pulls open channels, allowing ion influx.
Which cochlear region (base or apex) is maximally displaced by low-frequency sounds?

Apex (near the helicotrema). Basilar membrane is more flexible at apex, resonating with low frequencies.
What is tonotopic organization in the auditory system?

Spatial mapping of sound frequency along the basilar membrane and beyond. This organization preserves frequency information through topographic mapping from cochlea to cortex for precise sound perception.
What is tonotopic organization in the cochlea?

Different frequencies peak at different basilar membrane locations. Frequency map along cochlea's length.
Which membrane contacts stereocilia to produce shearing forces during sound transduction?

Tectorial membrane. Creates differential motion between hair cells and this gel-like structure.
Which basilar membrane region responds best to low-frequency sounds?

Apex of the cochlea (near helicotrema). Flexible basilar membrane at apex resonates with low frequencies.
What is the superior olivary complex primarily used for in auditory processing?

Sound localization using binaural cues (interaural time and level differences). This complex compares inputs from both ears to compute spatial location based on timing and intensity disparities.
What is the organ of Corti, and what is its key role in hearing?

Sensory epithelium on basilar membrane; contains hair cells for transduction. Hair cells convert mechanical deflection to electrical signals.
What structure separates the external ear from the middle ear?

Tympanic membrane (eardrum). Vibrates when sound waves hit it, converting air pressure to mechanical motion.
What is the tectorial membrane, and how does it contribute to transduction?

Overlies hair cells; shearing with basilar membrane bends stereocilia. Its stationary position relative to the moving basilar membrane creates shear forces that activate hair cell transduction.
What is the function of the Eustachian (auditory) tube?

Equalizes middle ear pressure with atmospheric pressure. Opens during swallowing/yawning to prevent pressure buildup.
What is the primary auditory cortical area that receives input from the medial geniculate nucleus?

Primary auditory cortex (A1) in the temporal lobe. Located in superior temporal gyrus, maintains tonotopic organization.
What are the three ossicles of the middle ear (in order from eardrum inward)?

Malleus → incus → stapes. The hammer, anvil, and stirrup form a lever system.
What is tonotopic organization in the auditory pathway?

Systematic mapping of sound frequency across neural structures. Preserves frequency organization from cochlea through cortex.
What is the auditory nerve, and where does it carry signals?

Cochlear branch of CN VIII carrying signals to the brainstem. Vestibulocochlear nerve transmits auditory signals centrally.
What is the major auditory cortex region that receives processed sound information?

Primary auditory cortex in the temporal lobe. Located in superior temporal gyrus (Brodmann areas 41/42).
What is the correct order of sound transmission from outer ear to inner ear structures?

Pinna → ear canal → tympanic membrane → ossicles → oval window → cochlea. Sound travels from outer structures through middle ear bones to inner ear fluid.
What is the primary function of the Eustachian tube in auditory physiology?

Equalizes middle-ear pressure with atmospheric pressure. Prevents pressure buildup that would dampen eardrum movement.
Which basilar membrane region responds best to high-frequency sounds?

Base of cochlea (near oval window). Stiffer basilar membrane vibrates best at high frequencies.
Which region of the basilar membrane responds best to high-frequency sounds?

Base of the cochlea (near the oval window). Stiff, narrow base resonates with high frequencies.
Identify the auditory pathway relay that is the first brainstem synapse for cochlear nerve input.

Cochlear nucleus. Located in medulla, processes timing and frequency information.
What membrane in the cochlea is displaced by stapes movement at the oval window?

Basilar membrane (via pressure waves in the scala vestibuli). Oval window pushes perilymph, creating traveling wave along membrane.
What is the role of the Eustachian tube in hearing physiology?

Equalizes middle-ear pressure with atmospheric pressure. Prevents barotrauma and optimizes sound transmission efficiency.
What is the auditory nerve, anatomically, and what does it carry?

Cochlear branch of CN VIII carrying action potentials from hair cells. Vestibulocochlear nerve transmits auditory information to brainstem.
Which cranial nerve carries auditory information from the cochlea to the brainstem?

Vestibulocochlear nerve (CN VIII), cochlear branch. Auditory division of the eighth cranial nerve.
What is the main function of the superior olivary complex in auditory processing?

Sound localization using interaural time and intensity differences. Compares inputs from both ears to determine sound direction.
What midbrain structure is a major relay and integrator for auditory information?

Inferior colliculus. It integrates binaural information and coordinates reflexes, serving as a hub before thalamic relay.
What is the main role of the middle ear ossicles in sound transmission?

Amplify and transmit vibrations to the oval window. Lever action increases force while reducing displacement.
Identify the inner-ear fluid compartments: which fluid fills the scala vestibuli and scala tympani?

Perilymph. This fluid surrounds the cochlear duct in the bony labyrinth.
What is the primary function of the ossicles in hearing?

Amplify and transmit vibrations to the oval window. They act as a mechanical lever system, increasing force by ~20x.
What is the main cue for sound localization in the horizontal plane for low-frequency sounds?

Interaural time difference (ITD). Brain detects which ear hears sound first.
What are the three middle-ear ossicles in order from tympanic membrane to oval window?

Malleus → incus → stapes. These tiny bones form a lever system that amplifies sound vibrations.
What is the key binaural cue used to localize low-frequency sounds?

Interaural time difference. Sound reaches the nearer ear microseconds before the farther ear.
Where is the primary auditory cortex located in the cerebrum?

Temporal lobe (Heschl gyrus; superior temporal gyrus). Located in this region, it performs advanced processing like sound recognition and maintains tonotopic maps.
Which region of the basilar membrane responds best to low-frequency sounds?

Apex of the cochlea (near the helicotrema). Wide, flexible apex resonates with low frequencies.
Which cochlear region responds best to high-frequency sounds: base or apex?

Base of the cochlea. The stiff, narrow base resonates with high frequencies.
Which cue is primarily used for localizing high-frequency sounds: ITD or ILD?

Interaural level difference (ILD). High frequencies create head shadow, causing volume differences between ears.
What is the basilar membrane, and what is its role in pitch perception?

Cochlear membrane whose location of peak vibration encodes pitch. Different regions vibrate maximally at different frequencies.
Which three ossicles transmit vibrations through the middle ear, in order?

Malleus incus stapes. These tiny bones connect from eardrum to inner ear.
Where is the primary auditory cortex located?

Superior temporal gyrus (Heschl gyrus) of the temporal lobe. Transverse temporal gyri process basic sound features.
Which pathway describes the standard ascending auditory route to cortex (major waystations)?

Cochlea → CN VIII → cochlear nuclei → sup. olive → inf. colliculus → MGN → A1. MGN = medial geniculate nucleus; A1 = primary auditory cortex.
What is the direction of hair-cell membrane potential change when stereocilia are deflected toward the tallest cilia?

Depolarization. Tip links pull open mechanically-gated ion channels when bent this way.
What is the oval window, and what does it transmit vibrations into?

Membrane at cochlea entrance; transmits vibrations into cochlear fluid. It serves as the interface where ossicle movements create pressure waves in the perilymph for cochlear stimulation.
Which part of the basilar membrane responds best to high-frequency sounds?

Base of the cochlea (near the oval window). Stiff, narrow membrane vibrates best at high frequencies.
What is the function of the round window in the auditory system?

Relieves pressure in cochlear fluid by bulging outward. Allows fluid movement since cochlear fluid is incompressible.
What structure collects and funnels sound waves into the external auditory canal?

Pinna (auricle). The outer ear's visible part captures and directs sound waves inward.
Identify the hearing loss type caused by damaged hair cells after chronic loud noise exposure.

Sensorineural hearing loss. Damage to cochlear hair cells or auditory nerve causes this type.
What are the three auditory ossicles, in order from tympanic membrane to oval window?

Malleus, incus, stapes. Also known as hammer, anvil, and stirrup respectively.
Identify the correct pathway order: outer ear to inner ear structures that transmit sound.

Pinna → canal → tympanic membrane → ossicles → oval window. Sound travels through outer ear, middle ear, then inner ear structures.
What is the basilar membrane, and what key auditory property does it encode?

Cochlear membrane whose place of vibration encodes frequency. Different regions vibrate maximally at different frequencies.
What is the primary auditory cortex location responsible for initial cortical sound processing?

Primary auditory cortex in the temporal lobe (Heschl gyrus). Located in superior temporal gyrus, processes basic sound features.
Which cochlear region responds best to high-frequency sounds: base (near oval window) or apex?

Base (near oval window). The stiff, narrow base vibrates best with high frequencies.
Which part of the basilar membrane responds best to low-frequency sounds?

Apex of the cochlea (near the helicotrema). Apex is wide and flexible, resonating with low frequencies.
What is the function of the Eustachian tube in hearing physiology?

Equalizes middle-ear pressure with atmospheric pressure. Prevents pressure buildup that would impair eardrum movement.
What is the key mechanical role of the ossicles in hearing?

Impedance matching; amplifies pressure at the oval window. Converts air vibrations to fluid vibrations efficiently.
Which ion is primarily responsible for depolarizing cochlear hair cells?

$K^+$ influx from endolymph. Endolymph's high $K^+$ concentration drives depolarization.
What is the oval window, and what does it transmit vibrations into?

Membrane contacted by stapes; transmits vibrations into cochlear fluid. Interface between middle ear bones and inner ear fluids.
What is the main perceptual correlate of sound wave amplitude?

Loudness (perceived intensity). Greater amplitude increases hair cell stimulation and neural firing rate, leading to heightened perception of volume.
What structure contains the hair cells that transduce sound into neural signals?

Organ of Corti. Located on the basilar membrane within the cochlear duct.
What is the primary function of the tympanic membrane in hearing?

Converts air pressure waves into mechanical vibrations. The eardrum vibrates in response to sound waves, initiating mechanical transduction.
Which cochlear structure contains the hair cells that perform auditory transduction?

Organ of Corti. Contains the sensory hair cells on the basilar membrane.
What is the function of the Eustachian (auditory) tube in the ear?

Equalizes middle ear pressure with atmospheric pressure. Opens during swallowing/yawning to prevent pressure buildup.
What is the function of the ossicles in auditory processing?

Amplify and transmit vibrations to the oval window. Mechanical advantage increases force while reducing displacement.
What ionic change most directly depolarizes cochlear hair cells when stereocilia bend?

K $^+$ influx from endolymph through mechanically gated channels. High $K^+$ in endolymph drives depolarization when channels open.
What is the immediate effect of stereocilia bending toward the tallest stereocilium?

Mechanically gated channels open, causing hair-cell depolarization. Tip links pull channels open, allowing K+ influx and depolarization.
Where is the primary auditory cortex located?

Temporal lobe (Heschl gyrus; superior temporal gyrus). Transverse gyri in superior temporal lobe process sound features.
What thalamic nucleus relays auditory information to the auditory cortex?

Medial geniculate nucleus (medial geniculate body). This nucleus filters and organizes auditory signals, ensuring refined input to cortical areas for perception.
What is the tectorial membrane, and how does it relate to hair cells?

Overlies hair cells; shear with basilar membrane bends stereocilia. Gel-like structure that hair cell tips embed into.
Identify which cochlear region encodes low-frequency sounds in place theory.

Apex of the cochlea (far from the oval window). Flexible basilar membrane resonates with low frequencies.
Which cochlear structure contains the sensory hair cells responsible for hearing?

Organ of Corti. This structure sits on the basilar membrane and contains hair cells.
Which midbrain structure is a major relay for auditory processing and reflexes?

Inferior colliculus. Integrates binaural input and mediates auditory reflexes.
Which cue is primarily used for localizing low-frequency sounds: ITD or ILD?

Interaural time difference (ITD). Low frequencies reach ears at slightly different times based on source location.
What is the cochlea, and what type of transduction occurs there?

Fluid-filled inner ear; mechanical vibrations neural signals. Spiral structure converts vibrations to nerve signals.
What are the three auditory ossicles in the middle ear, in order from tympanic membrane to oval window?

Malleus, incus, stapes. The hammer, anvil, and stirrup form the ossicular chain.
What is the correct pathway of sound conduction from outer ear to cochlea?

Pinna → canal → tympanic membrane → ossicles → oval window → cochlea. Sound travels through outer, middle, then inner ear structures sequentially.
What mechanical event directly opens hair-cell ion channels in the cochlea?

Deflection of stereocilia (tip-link tension change). Mechanical gating occurs when stereocilia bend toward tallest row.
What is the role of the round window in the cochlea?

Pressure relief membrane allowing cochlear fluid displacement. Without it, incompressible cochlear fluid couldn't move properly.
Which cochlear region responds best to low-frequency sounds: base or apex?

Apex of the cochlea. The wide, flexible apex resonates with low frequencies.
What is meant by tonotopic organization in the cochlea?

Different basilar membrane locations code different frequencies. Frequency-place mapping preserves pitch information spatially.
What is the organ of Corti, and where is it located?

Hair-cell sensory organ on the basilar membrane within the cochlea. Contains the actual hair cells that transduce sound into neural impulses.
What is the organ of Corti, and where is it located?

Sensory organ with hair cells; sits on the basilar membrane in cochlea. It contains specialized cells that detect basilar membrane movements, initiating neural signals for hearing.
Which two binaural cues are used for sound localization in the horizontal plane?

Interaural time difference and interaural level (intensity) difference. Brain compares arrival time and loudness differences between ears.
Identify the correct sequence of sound conduction from outer ear to cochlea.

Pinna → canal → tympanic membrane → ossicles → oval window → cochlea. Sound travels through outer, middle, then inner ear structures in this order.
Which ions primarily enter cochlear hair cells during mechanotransduction?

K $^+$ influx from endolymph (followed by Ca $^{2+}$ involvement). High $K^+$ endolymph drives depolarization uniquely.
Which cochlear region responds best to high-frequency sounds?

Base of the cochlea (near oval window). Basilar membrane is stiff at base, responding to high frequencies.
What thalamic nucleus relays auditory information to primary auditory cortex?

Medial geniculate nucleus (MGN). Thalamic relay station before cortical processing.
Which pitch theory best explains high-frequency sounds, and what is its core idea?

Place theory; pitch depends on maximal basilar membrane displacement location. Different frequencies peak at different basilar membrane locations.
What is the role of the oval window in auditory transduction?

Transfers stapes vibrations into cochlear fluid waves. Acts as the interface between air-conducted and fluid-conducted vibrations.
Identify the three ossicles of the middle ear in correct anatomical order.

Malleus → incus → stapes. These tiny bones connect sequentially to efficiently transfer vibrations from the eardrum to the inner ear.
Which cue primarily supports sound localization in the horizontal plane for high frequencies?

Interaural level (intensity) difference (ILD). Head shadow creates loudness differences between ears.
What midbrain structure is a key auditory relay involved in reflexive orienting to sound?

Inferior colliculus. Integrates binaural input for sound localization.
What fluid fills the scala media, and how does it differ from other cochlear chambers?

Endolymph; it is K $^+$ -rich relative to perilymph. High $K^+$ creates the endocochlear potential for transduction.
What is the main role of the ossicles in hearing?

Amplify and transmit vibrations to the oval window. Acts as a mechanical lever system to overcome impedance mismatch.
Identify the immediate neural pathway that carries signals from cochlea to brainstem.

Cochlear nerve (auditory branch of cranial nerve VIII). This nerve bundle transmits action potentials from hair cells to central auditory pathways for processing.
What fluid fills the scala vestibuli and scala tympani of the cochlea?

Perilymph. Low-potassium fluid similar to CSF in outer cochlear chambers.
What is the function of the round window in the cochlea?

Pressure release for fluid displacement in the cochlea. Allows incompressible cochlear fluid to move when stapes pushes.
Identify the key binaural cue used mainly to localize high-frequency sounds.

Interaural level (intensity) difference. Head creates sound shadow, making far ear quieter for high frequencies.
Identify the immediate mechanical event that opens hair-cell ion channels in hearing.

Stereocilia deflection that increases tip-link tension. Tip links physically pull open mechanosensitive channels.
What neurotransmitter is released by cochlear hair cells onto auditory nerve fibers?

Glutamate. Excitatory neurotransmitter at hair cell-nerve synapses.
What is the primary auditory cortex location for initial cortical processing of sound?

Heschl gyrus in the temporal lobe. Located on the superior temporal gyrus (Brodmann areas 41/42).
What is the tectorial membrane's key role in hair-cell mechanotransduction?

Shears stereocilia to open mechanically gated ion channels. Relative motion between membranes bends stereocilia during vibration.
What is the cranial nerve that carries auditory information from the cochlea to the brain?

Vestibulocochlear nerve (CN VIII). Cochlear division carries hearing; vestibular carries balance.
Which cue is primarily used for sound localization by interaural time differences (ITD)?

Low-frequency sounds. Phase differences between ears help localize low-frequency sources.
What is the immediate effect of stereocilia deflection toward the tallest cilium?

Mechanotransduction channels open; hair cell depolarizes. Ion channels open when stereocilia bend one way.
What is the cochlea, and what type of stimulus transduction occurs there?

Spiral inner-ear organ; mechanical vibrations transduced to neural signals. Fluid waves become neural signals via hair cell activation.
Which thalamic nucleus relays auditory information to the auditory cortex?

Medial geniculate nucleus (MGN). Thalamic relay station before cortical auditory processing.
What is the primary auditory cortex, and where is it located?

A1 in the temporal lobe (superior temporal gyrus). First cortical area for conscious sound processing.
What is the key binaural cue used to localize high-frequency sounds?

Interaural level (intensity) difference. Head creates acoustic shadow, making sound quieter on far side.
What structure is the external auditory canal, and what is its main role?

Ear canal; conducts sound waves to the tympanic membrane. This canal channels sound vibrations inward, protecting and guiding them to the eardrum for further processing.
What is tonotopic organization in the auditory system?

Systematic mapping of sound frequency across cochlea and auditory cortex. Preserves frequency information spatially throughout auditory pathway.
Where is the primary auditory cortex located?

Temporal lobe (Heschl gyrus; superior temporal gyrus). Located in superior temporal lobe, processes basic sound features.
What is the main perceptual correlate of sound wave frequency?

Pitch. Frequency determines basilar membrane vibration site, which correlates with the subjective experience of tone height.
What is the primary role of the ossicles in sound transmission?

Amplify and transmit vibrations to the oval window. Lever system increases force by ~20x for impedance matching.
What is the main cue for sound localization in the horizontal plane for high-frequency sounds?

Interaural level (intensity) difference (ILD). Head shadow makes sound louder in one ear.
What is the correct anatomical order of sound conduction from outer ear to cochlea?

Pinna → ear canal → tympanic membrane → ossicles → oval window → cochlea. Sound travels through outer, middle, then inner ear structures sequentially.
What are the three main parts of the ear, from outermost to innermost?

Outer ear, middle ear, inner ear. Sound travels through these regions sequentially for processing.
Which cue primarily supports sound localization in the horizontal plane for high frequencies?

Interaural intensity (level) difference. Head shadow creates loudness differences between ears.
What is the correct order of structures that sound waves pass through to reach the cochlea?

Pinna → ear canal → tympanic membrane → ossicles → oval window → cochlea. Sound travels through outer ear, middle ear, then inner ear structures.
Which basilar membrane region responds best to high-frequency sounds?

Base of the cochlea (near oval window). Stiff basilar membrane at base resonates with high frequencies.
Which binaural cue is most important for localizing high-frequency sounds?

Interaural level difference (ILD). High frequencies are shadowed by the head, creating intensity variations that help pinpoint sound sources.
What is the function of the oval window in the auditory system?

Transmits stapes vibrations into cochlear fluid waves. It's the membrane where stapes pushes to create fluid waves in cochlea.
Identify the inner-ear fluid compartment: which fluid fills the scala media (cochlear duct)?

Endolymph. High-potassium fluid creates the electrical gradient for transduction.
What is the function of the Eustachian (auditory) tube?

Equalizes middle-ear pressure with atmospheric pressure. Connects middle ear to pharynx, preventing pressure-induced damage.
Which three bones form the ossicles of the middle ear?

Malleus, incus, stapes. These tiny bones connect the eardrum to the inner ear.
What are the three auditory ossicles in order from lateral to medial?

Malleus, incus, stapes. Named hammer, anvil, and stirrup for their shapes.
What is the function of the round window in the auditory system?

Relieves pressure by allowing cochlear fluid displacement. Fluid needs somewhere to bulge out when oval window pushes in.
What auditory coding mechanism primarily represents sound frequency (pitch) in the cochlea?

Place theory (location of maximal basilar membrane vibration). Different frequencies activate different cochlear locations.
What fluid-filled structure of the inner ear contains the sensory organ for hearing?

Cochlea. This spiral structure converts fluid waves into neural signals.
What is the role of the basilar membrane in pitch (frequency) perception?

Place coding: location of maximal vibration encodes frequency. Different frequencies peak at different basilar membrane locations.
What neurotransmitter is released by cochlear hair cells onto auditory nerve afferents?

Glutamate. Primary excitatory neurotransmitter at hair cell synapses.
What is the primary function of the tympanic membrane in auditory processing?

Converts air pressure waves into mechanical vibrations. The eardrum vibrates when sound waves hit it, creating mechanical motion.
What is the immediate result of stereocilia deflection toward the tallest stereocilium?

Mechanically gated channels open and hair cell depolarizes. K+ influx through tip links causes depolarization.
What is the correct pathway of sound conduction from outer ear to inner ear structures?

Pinna $ $ ear canal $ $ tympanic membrane $ $ ossicles $ $ oval window $ $ cochlea. Sound travels from outer structures through middle ear bones to inner ear fluid.
What is the primary function of the cochlea in the auditory system?

Converts fluid vibrations into neural signals (auditory transduction). Hair cells here convert mechanical waves to electrical signals.
What is the correct order of sound transmission from outer ear to cochlear transduction?

Pinna → canal → tympanic membrane → ossicles → oval window → cochlea. Sound travels through outer, middle, then inner ear structures sequentially.
What is the main function of the superior olivary complex in auditory processing?

Binaural integration for sound localization. Compares timing and intensity differences between ears.
What is the round window, and why is it necessary for hearing?

Pressure-release membrane that allows cochlear fluid displacement. Fluid is incompressible; needs outlet for wave propagation.
Which part of the basilar membrane responds best to high-frequency sounds?

Base (near the oval window). The base is stiffer and narrower, making it more responsive to rapid oscillations characteristic of high pitches.
Which cochlear structure contains the sensory hair cells for hearing?

Organ of Corti. Contains inner and outer hair cells that transduce mechanical to electrical signals.
What is the immediate ionic event that occurs when stereocilia bend toward the tallest cilium?

Mechanotransduction channels open and $K^+$ influx depolarizes the hair cell. Endolymph's high $K^+$ drives depolarization when channels open.
Where is the primary auditory cortex located?

Superior temporal gyrus (Heschl gyrus) of the temporal lobe. Also called A1, processes basic sound features tonotopically.
What is the main role of the ossicles in hearing?

Amplify and transmit vibrations to the oval window. They act as a lever system to increase force on the smaller oval window.
What is the function of the tympanic membrane in auditory transduction?

Vibrates in response to sound; drives ossicle motion. Converts sound waves to mechanical vibrations.
What is the function of the oval window in the auditory system?

Transfers stapes vibrations into cochlear fluid waves. Interface between middle ear bones and inner ear fluid.
Which basilar membrane region responds best to low-frequency sounds?

Apex of cochlea (near helicotrema). More flexible basilar membrane vibrates best at low frequencies.
What midbrain structure is a major auditory reflex and processing center in the auditory pathway?

Inferior colliculus. Integrates binaural input for sound localization and reflexes.
What is the volley principle in auditory coding?

Groups of neurons alternate firing to represent higher frequencies. Overcomes single neuron firing rate limits for mid-range frequencies.
Identify the cranial nerve that carries auditory information from the cochlea.

Vestibulocochlear nerve (CN VIII). The auditory division carries signals to the brainstem.
What is the round window, and what is its key function in the cochlea?

Pressure-release membrane allowing cochlear fluid displacement. Prevents pressure buildup by allowing fluid movement in cochlea.

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