Ear Anatomy & Physiology Flashcards

Which structure connects the middle ear to the nasopharynx and helps equalize pressure?

Answer: Eustachian tube

The Eustachian tube (auditory tube) connects the middle ear cavity to the nasopharynx, allowing pressure equalization on both sides of the tympanic membrane.

The oval window is a membrane-covered opening that connects which two structures?

Answer: Middle ear to inner ear

The oval window is a membrane-covered opening in the bony wall separating the middle ear from the inner ear, where the stapes footplate transmits vibrations.

Which type of hair cells in the cochlea are primarily responsible for active amplification of sound?

Answer: Outer hair cells

Outer hair cells (OHCs) are electromotile and provide active mechanical amplification of basilar membrane motion, boosting sensitivity by up to 40–60 dB.

What is the primary function of the round window in the cochlea?

Answer: To allow fluid pressure to dissipate after oval window displacement

The round window membrane flexes outward when the oval window is pushed inward, allowing incompressible cochlear fluid to move and basilar membrane displacement to occur.

Reissner's membrane separates which two compartments of the cochlea?

Answer: Scala vestibuli from scala media

Reissner's membrane forms the upper wall of the scala media (cochlear duct), separating it from the perilymph-filled scala vestibuli above.

The endolymph found in the scala media is unusual because it has a high concentration of which ion?

Answer: Potassium (K+)

Unlike most extracellular fluids, endolymph has a very high potassium ion concentration (~150 mM), which is essential for generating the endocochlear potential.

Which cranial nerve transmits auditory information from the cochlea to the brainstem?

Answer: CN VIII (vestibulocochlear nerve)

The cochlear branch of cranial nerve VIII (vestibulocochlear nerve) carries afferent signals from the spiral ganglion neurons to the cochlear nuclei in the brainstem.

What is the tonotopic organization of the cochlea, and where are high-frequency sounds processed?

Answer: High frequencies near the base, low frequencies near the apex

The cochlea is tonotopically organized: high-frequency sounds cause maximum basilar membrane displacement near the stiff basal end, while low frequencies peak near the flexible apex.

The tensor tympani muscle attaches to which ossicle and is innervated by which nerve?

Answer: Malleus; CN V (trigeminal)

The tensor tympani inserts on the handle of the malleus and is innervated by the medial pterygoid branch of the mandibular division of the trigeminal nerve (CN V3).

The acoustic (stapedial) reflex protects the cochlea from loud sounds by causing the stapedius muscle to do what?

Answer: Stiffen the ossicular chain, reducing low-frequency energy transmission

Stapedius contraction tilts the stapes and stiffens the ossicular chain, attenuating primarily low-frequency sounds reaching the cochlea by 10–15 dB.

Hair cell stereocilia are arranged in rows of increasing height. What happens when they are deflected toward the tallest row?

Answer: Tip links open mechanosensitive ion channels, depolarizing the hair cell

Deflection toward the tallest stereocilia stretches tip links, pulling open mechanosensitive (MET) channels so K+ and Ca2+ flow in, depolarizing the hair cell.

The pinna's primary role in sound localization involves which acoustic cue?

Answer: Spectral shaping of sound that helps determine elevation and front-back discrimination

The ridges of the pinna create direction-dependent spectral filtering (head-related transfer function) that the auditory system uses for vertical and front-back localization.

Which structure within the cochlea produces endolymph and maintains the endocochlear potential?

Answer: Stria vascularis

The stria vascularis, located on the lateral wall of the scala media, actively secretes endolymph and generates the +80 mV endocochlear potential that drives hair cell transduction.

What is the approximate frequency range of normal human hearing?

Answer: 20 Hz to 20,000 Hz

The normal human auditory frequency range is approximately 20 Hz to 20,000 Hz (20 kHz), with greatest sensitivity between 1,000 and 4,000 Hz.

Damage to outer hair cells most commonly results in which type of hearing loss pattern on an audiogram?

Answer: Sensorineural hearing loss, typically worse at high frequencies

OHCs at the basal (high-frequency) end of the cochlea are most vulnerable to noise and ototoxins, producing the classic high-frequency sloping sensorineural loss.

The helicotrema is located at which end of the cochlea and serves what function?

Answer: Apex; connects scala vestibuli and scala tympani so fluid can flow between them

The helicotrema is a small opening at the cochlear apex where the scala vestibuli and scala tympani communicate, allowing very-low-frequency fluid pressure to equalize.

Which of the three ossicles is directly attached to the tympanic membrane?

Answer: Malleus

The handle (manubrium) of the malleus is embedded in the fibrous layer of the tympanic membrane, making it the first ossicle to receive vibrations from the eardrum.

The impedance mismatch between air and cochlear fluid is overcome by the middle ear transformer. What is the primary mechanism?

Answer: Hydraulic lever effect from the large tympanic membrane area relative to the small oval window area

The tympanic membrane's area (~55 mm²) is about 17–20 times larger than the oval window (~3.2 mm²), concentrating force and providing most of the ~25–30 dB pressure gain needed to overcome the air-to-fluid impedance barrier.

Otoacoustic emissions (OAEs) are generated by which cochlear structure?

Answer: Outer hair cells

OAEs are sounds produced by the active electromotility of outer hair cells; they travel backward through the middle ear and can be recorded in the ear canal with a sensitive microphone.

The vestibular system detects head rotation using which sensory end organ?

Answer: Semicircular canals with crista ampullaris

The three semicircular canals detect angular (rotational) acceleration; their ampullae contain the crista with hair cells embedded in the cupula, which deflects with endolymph movement.