Exam 3: Ear Flashcards
Hearing (Audition)
-detecting sound waves and converting them into nerve impulses
Equilibrium (Balance)
-detect position of head
External Ear
-consists of auricle, external acoustic meatus and tympanic membrane
Auricle (Pinna)
- outer mass of tissue
- function: collects sound waves to external acoustic meatus
External Acoustic Meatus
- between auricle and tympanic membrane
- function: directs sound to tympanic membrane
Tympanic Membrane (Eardrum)
-function: move/vibrate auditory ossicles when sound waves vibrate membrane
Middle Ear
-lateral (external) boundary is tympanic membrane
-medial (internal) boundary is oval window and round window
-contains auditory ossicles (ear bones)
and auditory tube
Auditory Ossicles
- malleus (hammer), incus (anvil), stapes (stirrup)
- connects with oval window of inner ear (where sound waves are transmitted to inner ear)
- Function: transmit and amplify sound waves to inner ear
Auditory Tube
- connects middle ear with nasopharynx (upper throat
- function: equalizes pressure in middle ear
Popping sensation when changing altitudes
-Caused by auditory tube opening and releasing pressure
Inner Ear
-consists of bony labyrinth and membranous labyrinth
Bony Labyrinth
- spaces/cavities inside temporal bone
- consists of vestibule, semicircular canals, and cochlea
Membranous Labyrinth
- membranous sacs/tubes that rest inside the bony labyrinth
- consists of utricle, saccule, semicirular ducts, and cochlear duct (scala media)
Perilymph
- fluid between bony and membranous labyrinth
- similar to CSF (in composition and function)
Endolymph
- fluid inside membranous labyrinth
- different chemically from perilymph
- helps conduct sound waves
Vestibule
-oval central portion of bony labyrinth
Semicircular Canals
-three circular spaces/canals in bony labyrinth
Cochlea
-spiral chamber of bony labyrinth
Utricle
- sac inside vestibule
- membranous labyrinth
- involved in interpreting equilibrium
Saccule
- another sac inside vestibule
- membranous labyrinth
- involved in interpreting equilibrium
Semicircular Ducts
- three membranous tubes in semicircular canals
- membranous labyrinth
- involved in interpreting equilibrium
Cochlear Duct (Scala Media)
- membranous tube inside cochlea
- membranous labyrinth
- involved in hearing
- splits cochlea into two chambers
How is equilibrium information transmitted?
-through vestibular branch of vestibulocochlear nerve CN VIII
Scala Vestibuli
- above cochlear duct
- filled with perilymph
- part of cochlea (bony labyrinth)
- connects to oval window
Oval Window
-directs sound waves through scala vestibuli
Scala Tympani
- below cochlear duct
- filled with perilymph
- part of cochlea (bony labyrinth)
- connects to round window
Round Window
-excess sound waves leave inner ear through this
Spiral Organ (Organ of Corti)
- filled with endolymph
- contained in cochlear duct
- rests on basilar membrane
- contains hair cells with have stereocilla (touch tectorial membrane)
How sound waves travel
- when sound waves enter via the scala vestibuli, they vibrate a small portion of the basilar memrane
- when the basilar membrane moves the stereocilia of the hair cells touch the tectorial membrane
- bending of the stereocilia generates a nerve impulse
- nerve impulses are sent to the brain via the cochlear brance of the vestibulocochlear nerve CN VIII
- remaining sound waves are transferred to the scala tympani and exit the inner ear via the round window
Complete (Brief) Overview of Hearing
- Sound waves are collected by auricle, travel in external acoustic meatus, sent to tympanic membrane
- Vibration of tympanic membrane causes vibration of auditory ossicles, wich in turn vibrates the oval window
- Sound waves travel through the scala vestibuli and vibrates a portion of the basilar membrane (which is attached to spiral organ)
- Stereocilia of the hair cells bend against the tectorial membrane which generates a nerve impulse
- Nerve impulse is sent to the brain via the vestibulocochlear nerve CN VIII
- remaining sound waves are transferred to the scala tympani and leave the inner ear through the round window
Otitis Media
- inflammation of middle ear
- may occur after respiratory infection
- spreads to auditory tube
- pain and pressure in middle ear
- can rupture tympanic membrane
Myringotomy
- surgical procedure to to put in tubes in tympanic membrane
- for chronic ear infections
- help drain fluid in middle ear
Frequencies and Basilar Membrane
- low notes (frequencies) vibrate basilar membrane far away from oval window
- high notes (frequencies) vibrate basilar membrane close to oval window
