Auditory 1 Flashcards
Which two systems in the ear are interconnected?
Vestibular & Cochlear
Where does the stapes sit?
On the oval window
What is the function of the round window?
Pressure release valve
-round window & oval window move in opposite directions
What is the mechanical portion to push the fluid in the ear?What is made of?
OSSICLES
- BONE
How is sound produced?
Sound is produced by vibrations
- cause the alternating compression and decompression of the surrounding air
What happens if the information traveling in the sound wave is interrupted before it reaches the Cerebral cortex?
IT NEVER HAPPENED
What are the receptors of sound?
Hair cells, which are sensitive to movement
What hertz levels can humans perceive?
10-20,00 Hz
What membrane does air vibrate? What gets lifted up and down?
Tympanic Membrane
- Malleus is lifted up & down
What muscle equalizes air pressure in the ear? What innervates this muscle
Tensor Tympani
- CN V3
Where in the ear is the air pressure (sound waves) converted to mechanical energy? Which two structures are responsible for this?
- MIDDLE EAR
- Tympanic Membrane
- Ossicles
How does the middle ear communicate with the nasopharynx? (lies medial to the tympanic membrane..
AUDITORY TUBES (eustachian tube)
What is the site of chronic infections, Otitis Media?
AUDITORY TUBE
What forms the roof of the middle ear?
Temporal Bone
–> MIDDLE CRANIAL FOSSA
What 2 nerves travel through the middle ear cavity?
CN 7 & CN 9 (Tympanic Nerve)
What muscle helps attenuate sound? What cranial nerve innervates this muscle?
STAPEDIUS
CN 7
(for loud explosive sound)
What is the condition that makes sound be perceived as being louder?
Hyperacussis
- injury to Facial Nerve(7) such as Bell’s Palsy would paralyze Stapedius = cannot dampen sound
What is the black shadow found in the tympanic membrane?
Chorda Tympani nerve
Which 2 nerves are the only visible nerves during exam?
CN 7 (chorda tympani)
& CN 2 in the eye?
What is the inner ear composed of? Which portion is filled with perilymph? Endolymph?
- Bony Labyrinth = Perylymph
- Membranous labyrinth = Endolymph
(continuous with structures in vestibular system –> Semicircular Canals)
What contributes to the formation of the receptor potentials? Is it greater in potassium or sodium?
ENDOLYMPH
- greater in potassium
The oval window and round window are continuous in the Membranous Labyrinth. True or False?
FALSE
- they are continuous in the BONY LABYRINTH
What are the 3 ways are can be transducer? Which is MOST EFFICIENT?
- Air = poor conduct
- Osseus
- Ossicular (Air Conduction)
OSSICULAR IS MOST EFFICIENT*
What nerve enters the ear as 1 and splits into 2?
Vestibulocochlear -splits into Vestibular N. & Cochlear N
Once the cochlea nerve enters the spiral, what is it called?
MODIOLUS
What is the “hearing” structure? Where is it contained?
COCHLEA
- in the modiolus
What are the 3 structures of the cochlea? Which is the oval window, apex, and round window?
- Scala Vestibuli = Oval Window
- Helicotrema =apex
- Scala Tympani = Round Window
What are the 2 membranes in the cochlea? Which of these membranes does the Organ of Corti sit on?
- Basilar & Reisner’s
2. Organ of Corti sits on the BASILAR membrane
Where does the cochlear duct lie between? What membrane is above? Below?
Scala Vestibuli & Scala Tympani
- REISNERS = above
- Basilar = below
The Reisner’s membrane -s part of scala ____ and the Basilar membrane is part of Scala ______
- Reisner’s = VESTIBULI
2. Basilar = TYMPANI
The Basilar membrane is widest where?
widest at HELICOTREMA –> LOW pitch (hell)
narrow –> apex –> OVAL WINDOW
(break the window = high pitch)
(stiffest at the base)
Where are high pitches localized? Low?
high = near BASE where it is stiffest –> OVAL WINDOW
low = Apex where most flexible –> HELICOTREMA
(think guitar cords)
Loudness depends on what?
the number of action potentials
What important structure sits on the Basilar membrane? What takes place here?
ORGAN OF CORTI
- transduction of pressure waves takes place
What is the function of the outer hair cells & the inner hair cells? Which receive more innervation from the Cochlea?
- OUTER (3 rows)
- 10% of overall innervation of cochlea
- DISPLACEMENT sensitive
2. Inner (1 row) - 90% of overall innervation
- DETECT SOUND, VELOCITY SENSITIVE
Which are the only receptors which can be modified by CNS to change the length and stiffness, out or inner hair cells?
OUTER hair cells
inner cannot be modified by CNS
Which hair cells have more movement?
Outer = DISPLACEMENT sensitive
What opens the K+ channels in the hairs, causing depolarization?
BENING OF HAIR CELLS TOWARDS the Kinocilium
Bending AWAY from the Kinocilium results in what?
CLOSURE of K+ channels
& hyper polarization of hair cells
- decrease Neurotransmitter release
Where are the action potentials of the ear located?
BIPOLAR cells
- similar to the eye
What is the reason for the tonotopic map?
difference in stiffness & width of the BASILAR membrane
- map = perception of different sounds & frequencies
(high = base - narrow & stiff, low = apex - wide & floppy)
Where does the tonotopic map travel through?
- COchlear Nuclei
- Superior Olivary Nucleus
- trapezoid body
- LATERAL LEMNISCUS - Inferior Colliculi
- Medial Geniculate
- Cerebral Cortex (Herchel’s gyrus)
Is the auditory system bilateral or unilateral?
BILATERAL
- unless there is a lesion in 8 or cochlear nuclei–> person will not be deaf
What can cause deafness?
Lesion in 8 or in Cochlear nuclei
Where is Heschel’s gyrus? What is it responsible for?
TEMPORAL LOBE - AREA 41
- Auditory
What will result if one cuts the DCN or AVCN (Dorsal Cochlear N. or Anterior Ventral Cochlear Nuclei)
Unilateral deafness
past the nuclei - hearing is BILATERAL
Which is medial and which is lateral to ICP:
COchlear Nuclei
Vestibular Nuclei
Cochlear = LATERAL
Vestibular = Medial
How is hearing transmitted to the cortex?
- Cochlea
- Inferior Colliculus
- Medial Geniculate
- Cortex
What is achieved by PHASE LOCKING the hair cells & bipolar cells?
TEMPORAL RESOLUTION
What happens at the onset of Temporal Resolution and at the offset?
- fire Action Potentials at the initiation of sound
- hyperpolarize offset
push & pull back (rebound)
What is the term for the 50 microsecond delay between one ear and another?
Interaural Difference
What is the auditory region of the cortex? Which lobe is it found in?
Herchel’s Gyrus
- Temporal Lobe
- What is Wiernecke’s Area responsible for?
2. Broca’s?
- COMPREHENSION
2. Motor (speech output)
What is the pre-motor speech pathway in the brain? What two areas does it connect?
Arcuate Fasciculus
Connects Wiernecke’s area to Broca’s area
Damage to which area will cause a loss in understanding of VISUAL and SPOKEN language?
Wiernicke’s Area
Damage to which Area will cause a disruption in speech output & verbal production of language?
BROCA’s area
Lesions to what two areas can affect verbal output?
- Arcuate Fasciculus
2. Broca’s Area