MCAT Psychological Social Foundations Flashcards: 6a Auditory System Processing

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This deck focuses on 6a Auditory System Processing, giving you a quick way to review the definitions, rules, and examples that matter most for MCAT Psychological Social Foundations.

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Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What is the function of the round window in cochlear mechanics?

Answer: Pressure release membrane that permits fluid displacement. Allows cochlear fluid to move as oval window pushes inward.

Flashcard 2: What fluid fills the scala media (cochlear duct)?

Answer: Endolymph. High-potassium fluid creates voltage gradient for hair cell function.

Flashcard 3: What is the immediate mechanical event that opens hair-cell transduction channels?

Answer: Deflection of stereocilia (shearing against the tectorial membrane). Tip links pull channels open when stereocilia bend.

Flashcard 4: Which cue is primarily used to localize low-frequency sounds: ITD or ILD?

Answer: ITD (interaural time difference). Low frequencies wrap around head, preserving timing differences.

Flashcard 5: Identify the primary auditory cortex location in the brain.

Answer: Temporal lobe (Heschl gyrus; superior temporal gyrus). Located in the transverse temporal gyrus (Brodmann areas 41/42).

Flashcard 6: Which part of the basilar membrane responds best to low-frequency sounds?

Answer: Apex of the cochlea (near the helicotrema). Wide, flexible apex vibrates best with low-frequency sounds.

Flashcard 7: What is the main role of the ossicles in auditory transduction?

Answer: Amplify and transmit vibrations to the oval window. The lever action increases force to overcome fluid resistance.

Flashcard 8: What is the name of the nerve that carries auditory information from the cochlea to the brain?

Answer: Cochlear nerve (part of CN VIII, vestibulocochlear nerve). Auditory division of cranial nerve VIII carries sound information.

Flashcard 9: What thalamic nucleus relays auditory information to the primary auditory cortex?

Answer: Medial geniculate nucleus (medial geniculate body). Thalamic relay between midbrain and cortex.

Flashcard 10: What is the basilar membrane's key role in frequency discrimination?

Answer: Different locations resonate to different sound frequencies (tonotopy). Creates a frequency map along the cochlea's length.

Flashcard 11: What is the correct sequence of structures that sound waves pass through in the outer ear?

Answer: Pinna (auricle)  auditory canal  tympanic membrane. Sound travels from outside to eardrum through these structures.

Flashcard 12: Which inner ear structure is directly displaced by the stapes at the oval window?

Answer: Perilymph in the scala vestibuli of the cochlea. Stapes footplate pushes oval window, creating fluid waves.

Flashcard 13: What is the cochlea and what does it do in auditory transduction?

Answer: Fluid-filled spiral that converts vibrations into neural signals. Shaped like a snail shell with three fluid-filled chambers.

Flashcard 14: Identify the key brainstem relay nucleus that receives the first synapse from the auditory nerve.

Answer: Cochlear nucleus. First central synapse in the auditory pathway at the medulla.

Flashcard 15: What is the primary coding strategy for sound intensity (loudness) at the auditory nerve?

Answer: Increased firing rate and recruitment of more auditory nerve fibers. Louder sounds cause greater hair cell deflection and neural activity.

Flashcard 16: Which structure carries auditory information from the cochlea to the brainstem?

Answer: Cochlear nerve (auditory branch of cranial nerve VIII). Part of the vestibulocochlear nerve carrying auditory signals.

Flashcard 17: What brainstem nucleus is the first major relay for cochlear nerve input?

Answer: Cochlear nucleus. First central processing station in the medulla.

Flashcard 18: What is the correct order of sound transmission from outer ear to inner ear structures?

Answer: Pinna → ear canal → tympanic membrane → ossicles → oval window → cochlea. Sound waves travel through air-filled structures to fluid-filled cochlea.

Flashcard 19: What is the correct order of sound conduction structures from outer ear to cochlea?

Answer: Pinna → ear canal → tympanic membrane → ossicles → oval window → cochlea. Sound travels through outer, middle, then inner ear structures sequentially.

Flashcard 20: What is the primary neurotransmitter released by cochlear hair cells onto auditory nerve fibers?

Answer: Glutamate. Excitatory neurotransmitter activates spiral ganglion neurons.

Flashcard 21: What is the primary auditory cortex location in the brain?

Answer: Heschl gyrus in the superior temporal lobe. Also called transverse temporal gyrus or Brodmann area 41.

Flashcard 22: What structure contains the hair cells responsible for auditory transduction?

Answer: Organ of Corti (within the cochlear duct). Contains inner and outer hair cells on the basilar membrane.

Flashcard 23: Where is the primary auditory cortex located?

Answer: Superior temporal gyrus (temporal lobe). Heschl's gyrus in the superior temporal lobe.

Flashcard 24: What structure contains the hair cells that transduce sound in the cochlea?

Answer: Organ of Corti. Sits on basilar membrane and contains sensory hair cells.

Flashcard 25: What is the primary function of the ossicles in hearing?

Answer: 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.

Flashcard 26: What is the correct order of sound transmission from outer ear to inner ear fluids?

Answer: Pinna → canal → tympanic membrane → ossicles → oval window → cochlea. Sound travels through outer, middle, then inner ear structures sequentially.

Flashcard 27: What is the key ionic basis for cochlear hair-cell depolarization?

Answer: K$^+$ influx from endolymph through mechanically gated channels. Endolymph's high $K^+$ concentration drives depolarization when channels open.

Flashcard 28: What is the function of the Eustachian tube in the middle ear?

Answer: Equalizes middle-ear pressure with atmospheric pressure. Prevents barotrauma and maintains ossicle mobility.

Flashcard 29: What is the organ of Corti?

Answer: Sensory epithelium containing hair cells on the basilar membrane. Contains inner and outer hair cells that detect sound vibrations.

Flashcard 30: Which cochlear region responds best to low-frequency sounds: base (near oval window) or apex?

Answer: Apex. The wide, flexible apex vibrates best with low frequencies.

Flashcard 31: What is the function of the pinna (auricle) in auditory processing?

Answer: 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.

Flashcard 32: Which region of the basilar membrane responds best to high-frequency sounds?

Answer: Base (near the oval window). The stiff, narrow base vibrates best with high frequencies.

Flashcard 33: What is the immediate stimulus that opens mechanically gated channels in cochlear hair cells?

Answer: Deflection of stereocilia from basilar membrane vibration. Bending opens ion channels, depolarizing the hair cells.

Flashcard 34: What is tonotopic organization in the cochlea?

Answer: Different sound frequencies peak at different basilar membrane locations. Frequency-to-place mapping along the basilar membrane.

Flashcard 35: What is the function of the Eustachian tube in the auditory system?

Answer: Equalizes air pressure across the tympanic membrane. Connects middle ear to throat for pressure balance.

Flashcard 36: Which cue primarily supports sound localization in the horizontal plane for low frequencies?

Answer: Interaural time difference (ITD). Sound reaches ears at slightly different times.

Flashcard 37: What is the role of the basilar membrane in pitch discrimination?

Answer: Place coding via tonotopic vibration along its length. Different frequencies cause peak vibration at different membrane locations.

Flashcard 38: What is the main function of the superior olivary complex in auditory processing?

Answer: Sound localization using binaural timing and intensity cues. Compares inputs from both ears to determine sound direction.

Flashcard 39: Identify the membrane that hair cell stereocilia contact during cochlear vibration.

Answer: Tectorial membrane. Shearing between this and basilar membrane bends stereocilia.

Flashcard 40: Where is primary auditory cortex located anatomically?

Answer: Superior temporal gyrus (Heschl gyrus) in the temporal lobe. Also called A1; processes basic sound features.

Flashcard 41: Which three bones form the ossicles of the middle ear, in order from lateral to medial?

Answer: Malleus → incus → stapes. These tiny bones form a mechanical chain from eardrum to inner ear.

Flashcard 42: What is the medial geniculate nucleus, and what modality does it relay?

Answer: Thalamic relay nucleus for auditory information to cortex. All auditory information passes through this thalamic nucleus.

Flashcard 43: What is the primary function of the tympanic membrane in auditory transduction?

Answer: Vibrates in response to sound and drives ossicle movement. Converts sound waves to mechanical vibrations for the ossicles.

Flashcard 44: What is the function of the pinna (auricle) in hearing?

Answer: Collects and funnels sound into the auditory canal. Acts as a natural amplifier directing waves toward the ear canal.

Flashcard 45: What is the main role of the ossicles in auditory processing?

Answer: Amplify and transmit vibrations to the oval window. Lever action increases force by ~20x to overcome fluid resistance.

Flashcard 46: What is the specific sensory receptor cell type for hearing in the cochlea?

Answer: Hair cells. Mechanoreceptors that convert mechanical deflection to electrical signals.

Flashcard 47: What is the difference between place theory and frequency theory of pitch perception?

Answer: Place: location on basilar membrane; Frequency: firing rate matches sound frequency. Place uses spatial coding; frequency uses temporal coding of pitch.

Flashcard 48: Which cue is primarily used for sound localization by interaural level differences (ILD)?

Answer: High-frequency sounds (head shadow effect). Intensity differences from head blocking help localize high frequencies.

Flashcard 49: What is the thalamic relay nucleus for auditory information before cortex?

Answer: Medial geniculate nucleus (MGN) of the thalamus. All sensory info (except smell) relays through thalamus.

Flashcard 50: Identify which cochlear region encodes high-frequency sounds in place theory.

Answer: Base of the cochlea (near the oval window). Stiff basilar membrane vibrates best at high frequencies.

Flashcard 51: Identify the auditory cue primarily used to localize sounds in the horizontal plane.

Answer: Interaural time and interaural intensity (level) differences. Brain compares timing and loudness differences between ears.

Flashcard 52: Which part of the basilar membrane responds best to low-frequency sounds?

Answer: Apex of the cochlea (near the helicotrema). Wide, flexible membrane vibrates best at low frequencies.

Flashcard 53: Which cochlear structure contains the sensory hair cells for hearing?

Answer: Organ of Corti. Contains inner and outer hair cells that transduce sound.

Flashcard 54: What is the auditory nerve, anatomically, and what does it carry?

Answer: Cochlear branch of CN VIII; carries auditory afferent signals. Part of vestibulocochlear nerve that transmits sound signals to brain.

Flashcard 55: What is the immediate electrical result of mechanically opening hair-cell channels?

Answer: Hair-cell depolarization and increased neurotransmitter release. K+ influx depolarizes cells, triggering glutamate release.

Flashcard 56: What are the three middle ear ossicles in correct order from tympanic membrane to oval window?

Answer: Malleus → incus → stapes. Named from Latin: hammer, anvil, stirrup based on their shapes.

Flashcard 57: Identify the correct ascending auditory pathway from brainstem to cortex after CN VIII synapses in the cochlear nucleus.

Answer: Cochlear nucleus $$ superior olive $$ inferior colliculus $$ MGN $$ auditory cortex. Bilateral pathway with crossings at multiple brainstem levels.

Flashcard 58: Which cochlear region responds best to low-frequency sounds?

Answer: Apex of the cochlea (near helicotrema). Basilar membrane is flexible at apex, responding to low frequencies.

Flashcard 59: What is the main role of the ossicles in hearing?

Answer: Amplify and transmit vibrations to the oval window. Ossicles provide mechanical advantage to overcome fluid impedance.

Flashcard 60: Which cue is primarily used to localize high-frequency sounds: ITD or ILD?

Answer: ILD (interaural level difference). Head shadow creates intensity differences for high frequencies.

Flashcard 61: What is the function of the tympanic membrane (eardrum)?

Answer: Vibrates in response to sound; converts air waves to mechanical motion. Thin membrane that initiates mechanical transduction of sound.

Flashcard 62: What is the round window, and what is its key role in cochlear mechanics?

Answer: Pressure-release membrane that permits cochlear fluid displacement. This flexible membrane bulges outward to accommodate fluid shifts, preventing pressure buildup during sound transmission.

Flashcard 63: What neurotransmitter is released by cochlear hair cells onto auditory nerve fibers?

Answer: Glutamate. The excitatory neurotransmitter at hair cell-nerve synapses.

Flashcard 64: Which three middle-ear bones (ossicles) transmit vibrations to the inner ear?

Answer: Malleus, incus, stapes. These tiny bones amplify and transmit vibrations from eardrum to inner ear.

Flashcard 65: What is the cochlea, and what type of transduction occurs there?

Answer: 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.

Flashcard 66: What is the specific role of the stapes at the oval window?

Answer: Transmits ossicle vibrations into cochlear fluid via the oval window. The footplate pushes fluid in the cochlea, converting mechanical to fluid waves.

Flashcard 67: What is the primary role of the round window in the cochlea?

Answer: Pressure relief; allows cochlear fluid displacement. Must move opposite to oval window for fluid flow.

Flashcard 68: Which brainstem nucleus is the first major synapse for auditory nerve input?

Answer: Cochlear nucleus. Located in the medulla, it processes basic sound features.

Flashcard 69: What structure directly bends hair cell stereocilia during sound transduction?

Answer: Tectorial membrane (shearing against stereocilia). Relative motion between membranes bends stereocilia during vibration.

Flashcard 70: Which part of the basilar membrane responds best to high-frequency sounds?

Answer: Base of the cochlea (near the oval window). Stiff base resonates with high frequencies; flexible apex with low.

Flashcard 71: Identify the three ossicles of the middle ear in anatomical order from eardrum to oval window.

Answer: Malleus → incus → stapes. The hammer, anvil, and stirrup form the ossicular chain.

Flashcard 72: Which pitch theory best explains low-frequency sounds, and what is its core idea?

Answer: Frequency theory; auditory nerve firing rate tracks sound frequency. Neural firing synchronizes with low-frequency sound waves.

Flashcard 73: Which three bones make up the ossicles of the middle ear, in order from lateral to medial?

Answer: Malleus, incus, stapes. These tiny bones connect the eardrum to the inner ear.

Flashcard 74: Which structure is classically described as the first major brainstem relay for auditory input?

Answer: Cochlear nucleus. Receives direct input from spiral ganglion neurons.

Flashcard 75: What is the functional difference between the oval window and the round window?

Answer: Oval: input to cochlea; round: pressure release/compensation. Oval receives vibrations; round bulges out to accommodate fluid displacement.

Flashcard 76: What is tonotopic organization in the cochlea?

Answer: Specific basilar membrane locations respond to specific frequencies. Creates a frequency map along the cochlear length.

Flashcard 77: What is the function of the round window in the cochlea?

Answer: Pressure release; allows cochlear fluid displacement. Fluid must move somewhere when oval window pushes in.

Flashcard 78: What structure do cochlear hair cells sit on that vibrates tonotopically?

Answer: Basilar membrane. Its width and stiffness vary to create frequency selectivity.

Flashcard 79: Which part of the basilar membrane responds best to high-frequency sounds?

Answer: Base of the cochlea (near the oval window). Base is stiff and narrow, resonating with high frequencies.

Flashcard 80: What is the main role of the ossicles in auditory transduction?

Answer: Amplify and transmit vibrations to the oval window. Acts as an impedance-matching lever system.

Flashcard 81: Which midbrain structure is a major relay and reflex center for auditory information?

Answer: Inferior colliculus. Integrates bilateral input and mediates auditory reflexes.

Flashcard 82: What structure separates the outer ear from the middle ear?

Answer: Tympanic membrane (eardrum). This membrane vibrates when sound waves hit it, initiating the hearing process.

Flashcard 83: Which three bones form the ossicles of the middle ear?

Answer: Malleus, incus, stapes. These tiny bones form the ossicular chain in order from lateral to medial.

Flashcard 84: Which thalamic nucleus relays auditory information to the auditory cortex?

Answer: Medial geniculate nucleus (MGN). Final relay before auditory information reaches cortex.

Flashcard 85: What ion is primarily responsible for depolarizing cochlear hair cells when mechanosensitive channels open?

Answer: K$^+$ influx from potassium-rich endolymph. Endolymph has high $K^+$ concentration unlike typical extracellular fluid.

Flashcard 86: What is tonotopic organization in the cochlea?

Answer: Different sound frequencies peak at different basilar membrane locations. Creates a frequency map along the cochlea's length.

Flashcard 87: What is the first major brainstem nucleus that receives input from the auditory nerve?

Answer: Cochlear nucleus. It processes initial auditory input, extracting features like timing and intensity before relaying to higher centers.

Flashcard 88: What is the primary function of the pinna (auricle) in hearing?

Answer: Collects and localizes sound; funnels sound into the auditory canal. The outer ear structure helps determine sound direction and amplifies certain frequencies.

Flashcard 89: What is tonotopic organization in the cochlea?

Answer: Mapping of sound frequency to specific basilar membrane locations. Different frequencies peak at different basilar membrane positions.

Flashcard 90: Which brainstem nucleus is the first major synapse for auditory nerve fibers?

Answer: Cochlear nucleus. Located in medulla, it's where auditory nerve fibers first synapse.

Flashcard 91: Which part of the basilar membrane responds best to low-frequency sounds?

Answer: Apex (near the helicotrema). The apex is wider and more flexible, allowing it to vibrate maximally with slower waves of low frequencies.

Flashcard 92: What is the primary function of the tympanic membrane in auditory transduction?

Answer: Vibrates in response to sound and drives ossicle movement. Converts sound waves to mechanical vibrations for the ossicles.

Flashcard 93: What is the primary role of the round window in the cochlea?

Answer: Pressure release membrane that permits cochlear fluid displacement. Allows fluid movement when oval window pushes inward.

Flashcard 94: Which cochlear region responds best to high-frequency sounds?

Answer: Base of the cochlea (near oval window). Stiff basilar membrane vibrates to high frequencies.

Flashcard 95: What neurotransmitter is primarily released by inner hair cells onto the auditory nerve?

Answer: Glutamate. Excitatory neurotransmitter activates spiral ganglion neurons.

Flashcard 96: What is the basilar membrane, and what does it do during sound processing?

Answer: Vibrating cochlear membrane; performs frequency-based mechanical analysis. Its varying stiffness allows different sections to resonate at specific frequencies, enabling spectral decomposition of sound.

Flashcard 97: What are the three auditory ossicles in the correct anatomical order?

Answer: Malleus → incus → stapes. The hammer, anvil, and stirrup transmit vibrations sequentially.

Flashcard 98: Which cranial nerve carries auditory information from the cochlea to the brainstem?

Answer: Vestibulocochlear nerve (CN VIII), cochlear branch. The auditory division of the eighth cranial nerve.

Flashcard 99: What auditory coding mechanism primarily represents sound intensity (loudness)?

Answer: Rate coding and recruitment (more neurons active). Louder sounds cause faster firing rates and activate more neurons.

Flashcard 100: Which cortical area is the primary auditory cortex, and where is it located?

Answer: A1 in the superior temporal gyrus (temporal lobe). First cortical processing area for sound.