Lecture 34 - Ears Flashcards
What are the three parts of the ear?
Inner - Middle - Outer
What is the inner ear within?
Temporal bone
What is the middle ear within?
Petrous and tympanic portions of the temporal bone
What is the bony labyrinth of the inner ear filled with?
Perilymph
What is suspended in the perilymph?
Membranous labyrinth
What is the membranous labyrinth filled with?
Endolymph
Besides endolymph what else is within the membranous labyrinth?
Organs that transduce movement into neuronal signals
What are the two sections of the membranous labyrinth?
Vestibule and cochlea
What is within the vestibule?
Contains all organs of balance and orientation
What innervates the vestibule?
Vestibular branch of CN VIII
What is within the cochlea?
Contains the organ of hearing
What innervates the cochlea?
Cochlear branch of CN VIII
What are the two types of hair cells in the inner ear?
Kinocilium
– and –
Stereocilia
What is the kinocilium?
Tallest single projecting out of apex of hair cell
What are the stereocilia?
Array of progressively shorter projections lined up next to the kinocilium
What happens when the stereocilia toward the kinocilium?
Increase the firing rate of the sensory nerve
What happens if the stereocilia bend away from the kinocilium?
Decrease the firing rate
What are the two portions of the of vestibule?
Utricle and saccule
What are maculae?
Sheets of hair cells stimulated by linear accleration
Where are horizontal macula?
Utricle
Where are vertical macula?
Saccule
What are cristae?
Crests of hair cells stimulated by fluid flow around semicircular ducts in response to rotation
Where are crista?
Located in the ampulla at the end of the three semicircular ducts
What stimulates the spiral organ?
Sound waves transmitted from the surrounding perilymph into the endolymph
What decides where the sound is transferred from perilymph to endolymph?
Frequency
What is different about hearing in fish?
Sound waves pass through the body of the fish due to being about the same density of water - only need internal structures
What is different about hearing in air?
Waves lose energy in transfer from air to ear fluids needs to be amplified?
What amplifies sound on land?
Tympanic membrane
What are the three parts of the middle ear?
Tympanic membrane - Ear ossicles - Oval window
What is the function of the middle ear?
Transmit sound vibrations from lateral external ear to medial inner ear
What are the three ear bones?
Stapes - Incus - Malleus
What does the stapes articulate with?
The oval window
What does the stapes do?
Causes the vibrations in the perilymph of the inner ear