Anatomy slides final review Flashcards
master
At which end of the cochlea is the BM the narrowest and most tense
Basal end
The 3 devisions of the cochlear nuclei are what?
DCN
AVCN
PVCN
What are the 2 cochlear stimulus-related potentials?
Cochlear microphonic - AC potential which minics the stimulus
Summating potential - DC potential
Name the 3 membranous structures in the vestibular system
Semicircular ducts
utricle
saccule
What are the 4 bones comproising the temporal bone
Squamous
petrous
tympanic
mastoid
What structures is on the immediate inner side of the spiral ligament
Stria vascularis
What is the name of the tube that ventilates and drains the middle ear space
Eustachian OR auditory tube
What is the inner ear fluid that has a high concentration of potassium and low concentration of sodium
Endolymph
For vestibular hair cells, shearing toward the kinocilium has what action?
Excitatory - depolarization
The 2 basic classes of theories of hearing are _________ and ________
Place (resonsance) theory
Temporal (frequency) theory
What is the name of the medial wall of the middle ear space
Labyrinthine wall
What is the resonant frequency of the average adult ear canal
Approximately 3400Hz
In the vestibular system, type II hair cells have what shape
Test tube shape
Which of the cranial nerves innervates tensor tympani
V - Trigeminal nerve
What is the source and voltage of the endocochlear potential
Produces by the stria vascularis
voltage: +80 to +100 mV
What are the 3 factors involved in the ME impedance matching function?
Areal ration of TM to OW
Pressure = F/area, so force at OW is increased 17 times
Lever action of ossicles
articulation of ME bones increases force and decreases velocity for an increase in the Z ratio of about 1.3
Buckling of TM
increases pressure about 2x
The osseous structures in the vestibular system are the ______ and _______
Semicicular canals
vestibule
Describe the 2 types of connections in the CC
Homolateral and Heterolateral
Homo: one place in one hemisphere to same place in the other hemisphere
hetero: connect different places in each hemispehre
What is the fluid contained in Scala Vestibuli
Perilymph
What is the anatomical term meaning “toward the bottom”?
Inferior
The gelatinous structure in the semicircular canals into which the sterocilia are embedded is what?
cupula
What is the section that divides the body into anterior and posterior parts?
Coronal
What are the 2 major auditory nuclei of the LL
VNLL - monaural sound identification
DNLL - binaural sound localization
What is the name of the fluid contained in scala media
endolymph
which of the vestibular hair cells is surrounded by an afferent terminal (calyx)
Type I cells
What is the direction of the BM traveling wave?
Why does it move that way?
The traveling wave always moves from base to apex
this is because of the changing mass and stiffness characteristics of the BM from base to apex
The bony prominence on the medial wall of the ME is known as what?
promontory
The two crucial functions of the SOC are
Sound localization; mediation site for the acoustic reflex
What structure is formed by the tops of the hair cells, phalangeal processes of support cells, and the pillar cells?
Reticular lamina
What is the cochlear fluid with a high concentration of sodium and a low concentration of potassium
perilymph
The hair cell with a test tube shape is the ______
Outer hair cell
How do the semicircular canals on each side of the head operate?
The canals operate in opposition to each other:
Horizontals work oppositely, and the left posterior and right anterior (and vice-versa) work oppositely
What is the name of the bony core of the cochlea
modiolus
Describe the blood supply to the cochlea
cochlear blood supply proceeds from the labyrinthine (internal auditory) artery
The labrinthine artery is a branch of the anterior inferior cerebellar artery (a branch of the basilar artery)
Venous drainage is through the internal auditory vein
What is the name of cranial nerve X?
Vagus
What are the 3 parts of a nerve cell
Dendrites
Soma (cell body)
Axon
What is the name of the membrane that separates scala media from scala vestibuli?
reissner’s membrane
Describe the polarization directions of the otolith organs
Hair cell polarization in the saccule is away from the striola (line of polarity)
while polarization in the utricle is toward the stiola
What are neural tuning curves?
Tuning curves plot neural discharge rate as a function of frequency
they are a plot of the minimum stimulation level (across frequency) that brings about an increase in firing above the spontaneous rate (i.e. neural threshold of the fiber across frequency)
The thalamic auditory relay center is known as what?
MGB
What are the 3 effects of the outer ear on hearing
Protection of middle and inner ear structures
enhancement of mid and high frequencies
improved directional hearing
What are the 2 cell types in the organ of corti?
sensory cells - inner and outer hair cells
supporting cells - claudius, hensens, deiters, pillar, border, sulcus, and phalangeal cells
What is the role the olivocochlear bundle is belived to play?
Improving detection in noise protecting against noise damage
expanding the dynamic range improving auditory attention
The primary auditory cortex is located where?
On the superior surface of the superior temporal gyrus
(heschl’s gyrus)
The grooves and ridges which can be used as landmarks on the cerebrum are known as what?
Sulci (grooves)
Gyri (ridges)
What membrane separates scala media from scala tympani?
BM
List the major nuclei of the ascending auditory pathway
CN
SOC
IC
MGB
PAC
Head rotaion along the X,Y, and Z axes are referred to as what?
X - roll
Y - pitch
Z - yaw
Describe the tectorial membrane, including its connections
The tectorial membrane is a gelatinous structure (about 95% water) which overlies the organ of corti
it is tightly connected to the limbus on the medial edge and loosely connected to the tops of the hensen’s cells on the lateral edge
Which of the nuceli in the SOC is largest in humans
MSO
What is the name of the stucture which attaches the cochlear duct to the bony outer wall of the cochlea
Spiral ligamnet
What happens when the inner hair cells are activated
neurotransmitters are released
Name the 3 chambers of the middle ear space
Tympanic cavity
Epitympanic recess
Mastoid antrum
How many inner and outer hair cells are there in the human ear
There are about 3500 IHC
About 12,500 OHC
What is the name of the structure that is seated on the BM
organ of corti
What is the name of the muscle that is attached to the manubrium of the malleus?
TT
The otolith organ responsible for movement in the horizontal plane is what?
Utricle
What are the 2 cochlear resting potentials
Intercellular potential
-40 mV for IHC
-70 mV for OHC
Endocochlear potential
+80 to 100 mV
Which of the hair cells has a flask shape
IHC
The auditory central nervous system is organized into two major paths, which are what?
Sound localization
Sound Identification
What is the relationship between spontaneous neural discharge rate and threshold level?
Neurons with high spontaneous rates have lower thresholds and neurons with low spontaneous rates have higher thresholds
The principle (although not sole) generator of wave V of the ABR is what?
LL
The hair cell bodies are bathes in ________, while the stereocilia are bathes in ________
perilymph
Endolymph
The major descending projection of the central auditory system is what?
Olivocochlear system which projects from the SOC to the cochlea
What os the name of the gelatinous structure that overlies the hair cells?
Tectorial membrane
The stucture which lies ddeep within the lateral suclus and connects to both the primary auditory and association areas (and is believed to play a variety of roles in aduitory processing) is known as what?
insula
What are the landmarks of the auricle 7
Helix
Antihelix
Tragus
Antitragus
Triangular Fossa
Concha
Lobule
About how many primary auditory neurons are in the human ear?
How many of these are afferent?
30,000 primary auditory neurons in the human ear
95% are afferent
The two sections of the BM are known as what
Zona arcuata
Zona pectinata
Describe the tonotopic organization of the auditory branch of CN VIII
Fibers innervating the apical hair cells form the center of the bundle while fibers innervating the basal hair cells form the outside of the bundle
What is the term that describes the frequency to place oragnization seen in the auditory system
tonotopy or tonotopic organization
What do we call collections of nerve fibers and cell bodies in the periphery and the central nervous system?
Nerves in the periphery are made up of nerve fibers or neruons
in the central nervous system, a collection of nerve fibers is called a tract
A collection of cell bodies in the periphery is called a ganglion
A collection of cell bodies in the CNS is called a nucleus
A neuorn identified as EI is one that has what stimulation
Excitatory input from the contralateral ear and inhibitory input from the ipsilateral ear
What are the names of the 2 sections of the tympanic membrane
pars tensa (3-4 layers)
Pars flaccida (2 layers)
Describe the two different types of afferent primary auditory neurons
About 95% of the afferent fibers are type I; these are large, myelinated bipolar neurons which contact the IHC
The remaining 5% of fibers are type II; these are small unmyelinated pseudo-monopolar neurons which contact the OHC
What happens when the medial olivocovhlear bundle is stimulated?
When the MOC is stimulated, the activity of the OHC is inhibited, so that sensitivity and tuning are reduced
Which of the cranial nerves innervates the stapedius muscles?
VII - facial nerve
Which of the 3 nuclei of the IC is responsive to auditory stimuli?
The 3 nuclei are the central (ICC), external (lateral) cortex, and the dorsal cortex
The ICC is the specific, core or lemniscal nucelus, which is responsive to sound.
The external cortex and dorsal cortex are the diffuse, belt or non-lemniscal nuclei, which integrate the auditory and non-auditory inputs
What is the primary generator of the cochlear microphonic
OHC
What is the name of the process in which the sterocilia of the hair cells are activated by the tectorial membrane?
Shearing
Describe the arcs of the acoustic reflex there are 2 ipsi 2 contra
- In one ipsilateral arc, the primary neuron projects to the ventral cochlear nucleus, the secondary neuron projects through the trapezoid body to the ipsi facial nerve nucleus, and the 3rd order neuron projects from the facial nerve nucleus to the ipsi stapedius
- In the other ispilateral arc, the primary neuron projects to the VCN, the secondary neuron projects to the ipsi SOC, the 3rd order neuron projects to the ipsi facial nerve nucleus, and the 4th order neuron projects to the ipsi stapedius
Contralateral Arcs:
- In one contralateral arc, the primary neuron projects to the ipsi VCN, the secondary neuron projects to the ipsi SOC, the 3rd order neuron projects to the contralateral facial nerve nucleus, and the 4th order neuron projects to contra stapedius
- In the other contralateral arc, the primary neuron projects to the ipsi VCN, the secondary neuron projects to the contra SOC, the 3rd order neuron projects to the contra facial nerve nucleus, and the 4th order neuron projects to the contra stapedius
The breaks in the myelin sheath along the neurons axon are known as what?
Nodes of ranvier
Describe the composition and linkages of the stereocilia?
Stereocilia are composed of actin filaments, which are cross-linked and tip-linked
The Tip-link play an important role in the transduction process
The hair cells of the otolith organs are located in what?
Maculae
What happens when the outer hair cells are “activated”
The OHCs become motile which “sharpens” the traveling wave, improving sensitivity and frequency resolution
Name the 3 middle ear bones
Malleus
Incus
Stapes
What is the name of the muscle that is attached to the stapes?
Stapedius
Name the cranial nerves
I. Olfactory
II. Optic
III. Oculomotor
IV. Trochlear
V. Trigeminal
VI. Abducens
VII. Facial
VIII. Vestibulocochlear
IX. Glossopharyngeal
X. Vagus
XI. Accessory
XII. Hypoglossal
What are the voltages of the intracellular resting potentials
The resting potential of the IHC is approx. -40 mV
And the resting potential of the OHC is approx. -70 mV
What do auditory neuron studies tell us about the auditory system and hearing
- Intensity is rate-coded
- Auditory nerve fibers are tuned in frequency
- Neural Discharge patterns are “phase-locked” for frequencies below about 4000-5000 Hz
What is the position of the manubrium of the malleus when viewing the right ear through an otoscope
Pointing toward 1 O’Clock
Describe the vestibulo-Ocular reflex
To maintain gaze, the VOR produces compensatory eye movements of the same magnitude, but opposition in direction, to the movement of the head
What are the major cues to localization in the horizontal plane?
Frequencies below 1900 Hz are diffracted, so cue is difference in interaural time of arrival
For frequencies above 1900 Hz , cue is interaural level difference
Describe Cranial Nerve VIII
Known as the auditory or vestibulocochlear nerve
Made up of 2 branches - 1 arising from the vestibular system and 1 from the cochlea
The afferent fibers innervate the hair cells and carry information toward the central system
The cell bodies of these neurons make up the spiral ganglia
The efferent fibers are the terminations of the olivocochlear bundle.
Most of the neurons in the vestibulocochlear nerve are bipolar
What is the name of the ligament that supports the stapes footplate in the oval winow
Annular ligament
What happens when the sterocilia of the hair cells are sheared?
Ions flow into the cells
Neurons may be classified in three groups. These are _________
Sensory
Motor
Interneurons
Damage to the synaptic junction between the hair cells and the auditory nerve results in
The condition known as synapotopathy or “hidden hearing loss” becasue it does not elevate thresholds, but rather is associated with problems on more omplex auditory tasks, such as speech recognition in noise
Name the eye muscles
Superior rectus muscle
Inferior rectus muscle
Lateral rectus muscle
Medial rectus muscle
Superior oblique muscle
Inferior Oblique muscle
Name the 3 channels of the inner ear
Scala Vestibuli
Scala Media
Scala Tympani
What is the resonant frequency of the middle ear?
1200 Hz
Idetify stuctures of the organ of corti
