Anatomy Key Points

Question 1

ET functions

Answer 1

Ventilation ME
Drainage ME
Protection Nasopharyngeal sounds

Question 2

Eustachian tube muscles

Answer 2

Tesnor Veli Palatini
Levator Veli Palatini
Salpingopharyngeus
Tensor Tympani

Question 3

Name and function of cranial nerves
a. CN 1
b. CN II
c. CN III
d. CN IV
e. CN V
f. CN VI
g. CN VII
h. CN VIII
i. CN IX
j. CN X
k. CN XI -
l. CN XII -

Answer 3

a. CN 1 - Olfactory, sensory, smell
b. CN II - Optic, sensory, vision
c. CN III - Occulomotor, motor, elevation and adduction of eye muscles
d. CN IV - Trochlear, motor, depression of adducted eye muscles
e. CN V - Trigeminal, mixed, facial sensation
f. CN VI - Abducens, motor, lateral rectus eye muscle
g. CN VII - Facial, mixed, taste buds and facial expressions
h. CN VIII - vestibulocochlear, mixed, balance and hearing
i. CN IX - Glossopharyngeal, mixed, taste, innervation of pharynx
j. CN X - Vagus, mixed, swallowing, vocal chords, GI and respiratory tracts
k. CN XI - Accessory, motor, neck and shoulder movement and pharynx and larynx muscles
l. CN XII - Hypoglossal, motor, tongue movement

Question 4

cranial nerves enter or exit the brainstem
a. CN 1-4,
b. CN 5-8,
a. 7 and 8
c. CN 9-12,

Answer 4

a. CN 1-4, above/around midbrain
b. CN 5-8, pons
a. 7 and 8 at cerebellopontine angle
c. CN 9-12, medulla

Question 5

Temporal fractures types and symptoms

Answer 5

a. longitudinal - accounts for 80%
1. Tears in skin of canal and ™
2. CHL (conductive hearing loss)—middle
ear/ossicular disruption
3. Facial nerve injury 10-25%
4. Parallels the long axis of the petrous pyramid of
the bone going from lateral to medial
b. transverse - accounts for 20%
1. SNHL
2. Vertigo or dizziness
3. Hemotympanum
4. Facial nerve injury 50%
5. Perpendicular to the petrous pyramid

Question 6

How does the sound reach and move through the outer ear? What function does the outer ear serve?

Answer 6

• Serves as a passive acoustic amplifier
  funnels the sound from the pinna to the EAC causing the ™ to vibrate
  sound reaches ear as sound wave that is changed to mechanical energy at ™
  *acoustic energy in air, pinna helps to act as funnel to direct down ear canal, **have two ears so capturing at two sides and have interaural differences (different intensity or phase), conduit (canal) resonating tube closed at one end that has a resonance that enhances sound at a regions important to us for speech (2,00 to 5,000 Hz), canal and pinna also server as protection

Question 7

What three main cranial nerves, innervate, pinna, and ear canal?

Answer 7

CN V, CN VII and CN X
5,7,10

Question 8

Three Ear Reflexs (NOT ART)

Answer 8

The Vagus Reflex/ Arnold’s reflex). This reflex often causes coughing, gagging, or watering of the eyes temporarily.

The Trigeminal Reflex/ Red reflex: Can cause excessive vascularization and thickening of the tympanic membrane from repeat, otoscopy, otoblock insertion or during early hearing aid acclimatization.

The Lymphatic Reflex. A slow reflex, This is evidenced by swelling of tissues and soreness in the canal. Often appears like an allergic reaction. may result over time particularly for new hearing aid or earmold users.

Question 9

How does the sound move through the middle ear and what is the function of the middle ear?

Answer 9

transfers acoustic to mechanical and pushed into the oval window
IMM - buckling ot ™, area difference from ™ to oval window, lever action
*™ vibration and ossicles, pushes mechanical vibration into inner ear (footplate to oval window), IMM - so we don’t lose sound, largest boost is area difference between ™ to footplate (spiked heel effect), buckling, and lever action of ossicles, air to mechanical and mechanical to hydraulic (pushing on fluid), would lose 99.9% almost all of energy without IMM to push the fluid in inner ear.

Question 10

Impedance matching

Answer 10

a. TM to oval window area ratio
b. Lever action of the ossicles
c. Buckling of the ™
Spiked heel affect
all three combined = 33db increase

Question 11

Perilymph

Answer 11

flow through a duct (perilymphatic duct) to reach the subarachnoid space and is thought to be a derivative of CSF- In Scala vestibule & Scala Tympani

Question 12

b. Endolymph

Answer 12

located inside scala media, produced by stria vascularis,

Question 13

List order of Cochlea Top to bottom. (scala media, Scala vestibula, scala tympani, Basilars membraneReissners membrane, )

Answer 13

Scala Vestibular - Perilymph
Reissners membrane - Divides SV & SM
Scala media - Endolymph
Basilar Membrane - Divides SM & ST
Scala Tympani- Perilymph

Question 14

Basilar membrane

Answer 14

Basilar Membrane - Forms the floor of the scala media, separating it from the scala tympani

Question 15

Stria vascularis

Answer 15

• maintains endolymph and producing an endocochlear potential (EP) in the scala media
  a highly specialized and vascularized tissue lining the lateral wall of the cochlea,

Question 16

Inner hair cells

Answer 16

single row of sensory receptor in Organ of Corti mainly sends afferent signals to the brainstem. Passive, above 40db

Question 17

Outer hair cells

Answer 17

cochlear Amplifier, Row of 3 to 4 hair cells that have their stereocilia embedded in the tectorial membrane. Active 40db

Question 18

Supporting cells
- unlikely questions-

Answer 18

Hensen’s cells, Deiters’ cells, inner and outer pillar cells, Claudius cells and inner supporting cells

Question 19

How is endolymph produced

Answer 19

in cochlea by the stria vascularis and dark cells in the vestibular

Question 20

Neuron Process

Answer 20

Dendrites- Dendrites receive information from other neurons. Receptor portion with spikes- spikes are to surface area
Soma- manuFact center for a cell with DNA, RNA and organelles
axon- treading portion sends action potentials along the neuron
terminal Bouton- end of axon branches, where the synapses will occur transmits information to other neurons at synapse

Question 21

How does CN VIII innervate the AV

Answer 21

a. Scarpa’s ganglia - vestibular nuclei
b. Spiral ganglia - cochlea nuclei
c. LSU on top and PS for where superior vestibular nerve and inferior vestibular nerve fibers innervate structures

Question 22

Describe the resting state of a neuron or receptor cell, including hair cells of the AVS

Answer 22

OHC function- biological mechanical amplifier, improve hearing by elongating and , IHC function - afferent info to the brainstem, the endocochlear potential (-45mV inside the IHC and +80 mV in endolymph = 125 mV difference to drive K+ into a simulated hair cell) difference drives positive potassium into the hair cell quickly to a stimulated IHC, resting

Question 23

What is a resting potential

Answer 23

Inner he’ll sit at a -45 resting potential

Question 24

True or False
IHC codes intensity by voltage change- Louder stimulus louder the voltage change= amplitude modulating calcium will dump more neurotransmitters

Answer 24

TRUE

Question 25

Describe the stimulation of receptor potentials in hair cells

Answer 25

a. Endocochlear potential - The +80mV potential of the endolymph with respect to the perilymph that is maintained by the stria vascularis pumping K+ ions into the endolymph
b. Shearing of stereocila
c. Influx of potassium (K+)
d. Trigger Ca++ channels in influx of Ca++
e. Dumping of neurotransmitters (e.g. glutamate)
-glutamate in audio/vestibular system (excitatory)
f. Synapse—terminal bouton to the next cell or effector organ

Question 26

True or False
Movement toward the tallest stereocilia depolarizes the cell, while movement in the opposite direction leads to hyperpolarization

Answer 26

TRUE

Question 27

When an auditory stimulus has stimulated inner hair cells and the receptor potential is sufficiently strong to reach its threshold, how is the information then passed from the hair cells to the CN VIII afferent fibers at the synapse? (Describe only what occurs at the synapse).

Answer 27

The voltage of the RP causes Calcium ion channels to open in the base of the inner hair cell. Ca++ rushes in and triggers the NT vesicles to move the the edge of the membrane and dump NT (i.e. Glutamate) into the synaptic cleft. The NT (which is a ligand/chemical) will cross the cleft and bind to receptor sites on the CN VIII cell membrane causing ligand-gated channels to open and depolarize the cell which would be an excitatory post-synaptic potential.=

Question 28

How is the resting membrane potential maintained in neurons such as CN VIII? (sodium Potassium pump)

Answer 28

By the active, energy consuming, sodium-potassium pump which pumps 3 sodium ions out of the cell and 2 potassium ions into the cell to maintain and re-establish the proper ion balance.

Question 29

Depolarization

Answer 29

Na+ sodium influx
What is the membrane potential less negative towards zero even beyond?

Question 30

Audiovestibular CANS - 8CSLIMA-structures and important functions at each level
* suspected Question*

Answer 30

8- CN 8 enters at CPA Synapses of CN Incoming CN 8 fibers
sending projections to cochlear nucleus divsions
C- Cochlear nucleus
- 3 divisons Anterior ventral, cochlear nucleus (AVCN),
Posterior ventral cochlear nucleus (PVCN), Dorsal
Cochlear Nucles (DVN)
S- superior olivary complex; AVCN,PVCN, DCN project to
SOC ipsilateral & contralateral. - first in CAN to recieve
binaural input.
- 2 divisons lateral superior olive (LSO) medial
superior olive (MSO).
-LSO receive processes, high frequency, localize
using ILD
- MSO received this is a low frequency information,
localizes using temporal cues
L- Lateral Lemniscus; SOC Ascending fibers connect to LL.
carries information from the cochlear nuclei to inferior
colliculus.
I- inferior Colliculus ;recieve input directly or indirectly
rom all lower portions
M- Medial Geniculate Body; Ventral, Dorsal and medial. V-
respond to acoustic stimuli, D & M, responsive to
somatosensory and acoustic stimulation
A- A1, Primary Auditory Cortex; auditory radiation, go to the primary auditory cortex and receive auditory information

Question 31

Structure in the CANS Pathway

Answer 31

8- Cranial Nerve 8
C- Cochlear nucleolus
S- superior olivary complex
L- lateral Lemniscus
I- inferior colliculus
M- Medial Geniculate Nucleus
A- A1 or primary auditory cortex

Question 32

Along the central auditory nervous system (CANS) pathway, the long bundle of axons that carries ascending information from the cochlear nuclei up to the inferior colliculus in the brainstem (with possible synapses along the way) is known as the ….

Answer 32

Lateral Lemniscus

Question 33

Along the central auditory nervous system (CANS) pathway, first set of nuclei in the brainstem to receive binaural information are the….

Answer 33

Superior Olivary Complex

Question 34

How is the resting membrane potential maintained in neurons and muscle fibers?

Answer 34

By the action of the sodium-potassium pump which actively takes 3 sodium ions out of the cell and 2 potassium ions in to maintain and re-establish the proper ion balance

Question 35

Structure in the CANS Pathway
* suspected Question*

Answer 35

8- CN 8
V- Vestibular Nuclei Ipsilateral
V- Vestibular Nuclei contralateral
C- Cerebellum
R- Reticular formation
O- Occular Muscles Via (CN 3,4,6)
S- Spinal Cord (LVST,MVST)
S- Superior Sylvian Gyrus and SI areas
(ALL AT ONCE)

Question 36

GABA neurotransmitter

Answer 36

Inhibatory

Question 37

Glutamate

Answer 37

Excitatory

Question 38

Acteylcholine

Answer 38

possible transmitter descending pathway

Question 39

Vestibular central Pathway- 8VVCROSS structures and important functions at each level
* suspected Question*

Answer 39

8- CN 8
V- Vestibular Nuclei Ipsilateral
V- Vestibular Nuclei contralateral
C- Cerebellum
R- Reticular formation
O- Occular Muscles Via (CN 3,4,6)
S- Spinal Cord (LVST,MVST)
S- Superior Sylvian Gyrus and SI areas
(ALL AT ONCE)

Question 40

afferent innervation of the cochlea from CN VIII neurons?

Answer 40

Many afferent fibers synapse on a single inner hair cell so the information diverges onto many neurons

Question 41

IHC

Answer 41

Main Sensory/Afferent Fibers
1 IHC synapses onto 10 different CN 8 Fibers
Infant diverges to many neurons from one outer hair cell

Question 42

OHC

Answer 42

Ampifers
1 CN 8 Fiber branching & innervating Mulitple OHC
Informaton from Many outer hair cells, converge onto one neuron