Inner Ear Anatomy and Hearing Mechanisms Quiz

Sound Transmission and Perception in the Ear

• Intensity of sound is determined by the difference in air pressure and is measured in decibels (db)
• Higher intensity results in louder sound due to higher air pressure and vice versa
• The external ear includes the pinna, external auditory canal, and tympanic membrane
• The middle ear consists of the tympanic cavity, auditory ossicles, and the auditory tube
• The auditory ossicles, including the malleus, incus, and stapes, transmit sound vibrations to the inner ear
• The inner ear contains the cochlea for hearing and the vestibular apparatus for balance
• The bony labyrinth and membranous labyrinth within the inner ear are interconnected fluid-filled spaces
• The cochlea is a coiled, tubular space within the bony labyrinth, containing the scala media, scala vestibuli, and scala tympani
• The cochlear duct, suspended within the cochlea, subdivides the cochlear space
• The cochlea contains the spiral organ, which is responsible for sound perception
• The auditory system is a complex structure involving the transmission and perception of sound waves
• Understanding the anatomy and physiology of the ear is crucial for comprehending the mechanisms of hearing and balance

Anatomy and Function of the Inner Ear

• The basilar membrane (BM) separates the scala media from the scala tympani and contains the spiral organ, which is the sense organ of hearing.
• The spiral organ, located on the basilar membrane, contains hair cells and support cells, with afferent nerve fibers monitoring the hair cells.
• The hair cells transduce sound energy into action potentials in the afferent nerves, with stereocilia on the hair cells bending to open or close channels, leading to depolarization or hyperpolarization of the hair cell.
• The cochlea, uncoiled, has the oval window at the base of the scala vestibuli and the round window at the base of the scala tympani, with pressure waves initiated in the fluid of the scala vestibule and relieved at the round window.
• The basilar membrane is optimally displaced at a certain point along its length by a specific frequency, thus organizing the spiral organ "tonotopically."
• Auditory pathways project bilaterally to the primary auditory cortex, with low-frequency sounds processed in the thalamus and high-frequency sounds in the medial geniculate nucleus.
• Deafness can be due to conduction issues involving the external or middle ear, or sensorineural issues involving the inner ear or cochlear nerve.
• The inner ear consists of the bony labyrinth and the membranous labyrinth, with the latter containing the sense organs of hearing and balance.
• The otolith organs, utricle and saccule, detect the static position and linear acceleration of the head using maculae with hair cells and support cells, and the otolith membrane containing calcium carbonate crystals.
• The otolith organs detect head position and linear acceleration by the distortion of stereocilia and alteration of neurotransmitter release.
• The semicircular ducts, three arranged at right angles to each other, contain hair cells in the crista ampullaris and detect angular acceleration of the head using the cupola's movement with the surrounding fluid.
• The semicircular ducts detect angular acceleration of the head by the distortion of hair cells and alteration of neurotransmitter release, providing information on head position and linear acceleration.