Nervous System: Senses - Anatomy of the Ear, Hearing, and Equilibrium

Flashcards covering the anatomy of the external, middle, and inner ear, the mechanism of hearing, auditory pathways, and the physiology of equilibrium.

Auricle

A funnel-shaped part of the external ear composed of elastic cartilage that protects the ear entryway and directs sound waves inward.

External acoustic meatus

The ear canal; a tube located between the auricle and the tympanic membrane.

Cerumen

An antimicrobial substance produced by ceruminous glands in the external acoustic meatus.

Tympanic membrane

Commonly known as the eardrum; a funnel-shaped membrane separating the external and middle ear that vibrates when hit by sound waves.

Auditory tube (Eustachian tube)

A passage extending from the middle ear to the nasopharynx that equalizes pressure on either side of the tympanic membrane.

Malleus

The auditory ossicle attached to the medial surface of the tympanic membrane that resembles a hammer.

Incus

The middle auditory ossicle resembling an anvil.

Stapes

The auditory ossicle resembling a stirrup with a disclike footplate that fits into the oval window.

Tensor tympani and Stapedius

Two small muscles that restrict auditory ossicle movement during loud sounds.

Otitis Media

Infection of the middle ear characterized by fluid accumulation and pressure; most often experienced by young children due to short, horizontal auditory tubes.

Perilymph

A fluid similar to interstitial fluid that fills the space between the bony and membranous labyrinths in the inner ear.

Endolymph

A fluid similar to intracellular fluid, rich in $K^+$, located within the membranous labyrinth.

Cochlea

The snail-shaped chamber of the inner ear that houses the membranous cochlear duct.

Vestibule

The part of the bony labyrinth containing two saclike membranous parts: the utricle and the saccule.

Semicircular canals

Regions of the bony labyrinth that contain the membranous semicircular ducts.

Helicotrema

A small channel located at the apex of the cochlea that connects the scala vestibuli and the scala tympani.

Spiral organ

A sensory structure for hearing within the cochlear duct consisting of hair cells and supporting cells on the basilar membrane.

Tectorial membrane

A gelatinous structure in the cochlear duct where the stereocilia and kinocilia of hair cells are embedded.

Tip link proteins

Proteins that connect the tips of inner hair cell stereocilia; they pull open ion channels to allow $K^+$ to diffuse into the cell when the basilar membrane moves.

Pitch

The sensation of a frequency, depending on the rate of vibration; high-frequency sounds excite cells in the stiff region of the basilar membrane near the oval window.

Decibels (dB)

The unit of measurement for sound intensity or loudness, where $0\,dB$ is the threshold for hearing.

Inferior colliculus

A midbrain structure in the auditory pathway that coordinates head orienting reflexes to sounds.

Superior olivary nucleus

A nucleus in the pons that localizes sound and initiates reflexive contraction of middle ear muscles.

Medial geniculate nucleus (MGN)

A part of the thalamus that filters auditory signals and relays them to the primary auditory cortex.

Conductive deafness

Hearing loss resulting from interference of wave transmission in the external or middle ear.

Sensorineural deafness

Hearing loss resulting from malfunctions in the inner ear or the cochlear nerve.

Vestibular apparatus

The collective name for the utricle, saccule, and semicircular ducts which monitor equilibrium.

Macula

The sensory receptor for static equilibrium and linear acceleration located in the utricle and saccule.

Otoliths

Calcium carbonate crystals that cover the gelatinous otolithic membrane in the macula.

Ampulla

The bulged region at the base of each semicircular canal containing the receptor for angular acceleration.

Crista ampullaris

The receptor for angular acceleration located within the ampulla, consisting of hair cells and support cells.

Cupula

A gelatinous, conical-shaped organ in the ampulla where hair cell stereocilia and kinocilia are embedded.

Vestibular nuclei

Nuclei in the superior medulla that process equilibrium signals to help control reflexive eye movements and balance.