Ear Flashcards
What are the names of the ossicles?
Malleus, incus and stapes
How can infection spread from nasopharynx to middle cranial fossa?
Nasopharynx to middle ear through Eustachian tube
Middle ear to mastoid air cells through aditus to mastoid antrum
Mastoid air cells to middle cranial fossa
What are the muscles that are involved in acoustic reflex?
Tensor tympani and stapedius
What is the function of the acoustic reflex?
Inhibit vibrations during loud noise - avoid damage
What nerve supplies tensor tympani?
Mandibular nerve
What nerve supplies stapedius?
Facial nerve
Which part of the temporal bone contains the inner ear?
Petrous part
What are the cochlea, vestibule and semicircular canal filled with?
Perilymph
What are the electrolyte levels in perilymph?
High potassium, low sodium (same as extracellular fluid)
What is the membranous labyrinth?
Epithelial sac within the vestibule, cochlea and semicircular canal
What is the membranous labyrinth filled with?
Endolymph
What are the electrolyte levels in endolymph?
Low potassium and high sodium (same as intracellular fluid)
What are the three types of sensory receptor in membranous labyrinth?
Maculae, christae ampullaris and spiral organ/organ of Corti
What is the function of maculae receptor?
Vestibular receptor
Balance, gravity, position - linear acceleration
What is the function of christae ampullaris?
Vestibular receptor
Angular acceleration/deceleration
Where are the maculae?
Saccule and utricle (parts of membranous labyrinth)
Where are christae ampullaris?
Semicircular ducts
What type of receptor is spiral organ?
Auditory receptor
What is the cochlear duct?
Part of membranous labyrinth in cochlea
How many times does the cochlea spiral around the bone axis?
2.5 times
What does the cochlear duct split the cochlea into?
Scala vestibule (above) and scala tympani (below)
Where are the scala vestibule and scala tympani continuous?
Apex of cochlea - helicotrema
Where is the oval window?
Between ossicles and scala vestibule
Where is the round window
At end of scala tympani
What frequency does the proximal basement membrane respond to?
High frequency
What frequency does the distal basement membrane respond to?
Low frequency
Where does information from the auditory pathway get projected to in cerebral cortex?
Heschl’s gyrus - temporal lobe
Where is the cell body of the primary neuron in the auditory pathway?
Spiral ganglion
Where does information in the auditory pathway cross the midline?
Trapezoid body (near pons)
Where does the information in the auditory pathway first get passed to in the brainstem?
Cochlear nuclei
Where is the information passed to after it has crossed the midline?
Superior olivary nuclei
After the superior olivary nuclei, where does the information in the auditory pathway go?
Inferior colliculi
Where does the information from the auditory pathway go in the thalamus?
Medial geniculate nuclei
Why is the auditory pathway bilateral?
To help localise sound - compare timing and volume
What is conduction deafness?
Problems conducting soundwaves in outer or middle ear
What is sensorineural deafness?
Damaged hair cells in cochlear or damaged vestibulocochlear nerve
