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AUD 503 - Anatomy Final
Terms in this set (98)
At which end of the cochlea is the basilar membrane the narrowest and most tense?
the basal end
The 3 divisions of the cochlear nuclei are what?
Dorsal CN, Anterior Ventral CN, Posterior Ventral CN
What are the 2 cochlear stimulus-related potentials?
Cochlear Microphonic (AC potential which mimics the stimulus) and Summating Potential (DC potential)
Name the 3 membraneous structures in the vestibular system
Semicircular ducts, article, saccule
What are the 4 bones comprising the temporal bone?
Tympanic, Mastoid, Petrous, Squamous (TMPS)
What structure is on the immediate inner side of the spiral ligament?
What is the name of the tube that ventilates and drains the middle ear space?
Eustachian (auditory) tube
What is the inner ear fluid that has a high concentration of potassium and a low concentration of sodium?
The 2 basic classes of theories of hearing are ___________ and ___________.
Place and temporal theory
Place (resonance) theory
Hemholtz & Bekesy; explains pitch perception on the basis of location on the basilar membrane at which hair cells are stimulated
Temporal (frequency) theory
pitch perception is determined by neural activity (firing rate of auditory nerve cells)
What is the name of the medial wall of the middle ear space?
What is the resonant frequency of the average adult ear canal?
Approximately 3400 Hz
Which of the cranial nerves innervates tensor tympani?
V - Trigeminal Nerve
What is the source and voltage of the endocochlear potential?
The endocochlear potential (EP) is produced by the stria vascularis. It's voltage is approximately +80 - +100mV.
What are the 3 factors involved in the ME impedance matching function?
1) Areal Ratio of TM to OW: pressure = force/area, so force at OW is increased 17 times (55/3.2)
2) Lever Action of Ossicles: Articulation of ME bones increases force and decreases velocity for an increase in the z ratio of about 1.3
3) "Buckling" of TM: TM buckling increases pressure about 2x
The osseous structures in the vestibular system are the ______ and ________.
1) Semicircular canals
Describe the two types of connections in the corpus callosum
The corpus callosum has homolateral and heterolateral connections. The homolateral connections connect one place in one hemisphere to the same place in the other hemisphere. The heterolateral connections connect different places in each hemisphere.
What is the fluid contained in scala vestibuli?
What is the anatomical term meaning "toward the bottom"?
What is the section that divides the body into anterior and posterior parts?
What are the 2 major auditory nuclei of the lateral lemniscus?
1) Ventral (VNLL) - mainly concerned with monaural sound identification
2) Dorsal (DNLL) - mainly concerned with binaural sound location
What is the name of the fluid contained in scala media?
What is the direction of the basilar membrane 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 basilar membrane from base to apex.
The bony prominence on the medial wall of the middle ear is known as what?
The two crucial functions of the superior olivary complex are:
1) Sound localization
2) Mediation site of the acoustic reflex
What structure is formed by the tops of the hair cells, phalangeal processes of support cells and the pillar cells?
What is the cochlear fluid with a high concentration of sodium and low concentration of potassium?
The hair cell with a test tube shape is the _________.
Outer hair cell
What is the name of the bony core of the cochlea?
Describe the blood supply to the cochlea.
Cochlear blood supply proceeds from the labyrinth (internal auditory) artery. The labyrinth 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?
What are the 3 parts of a nerve cell?
2) Cell body (soma)
What is the name of the membrane that separates scala media from scala vestibuli?
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. the neural "threshold" of the fiber across frequency
The thalamic auditory relay center is known as what?
Medial geniculate body
What are the 3 effects of the outer ear on hearing?
1) Protection of middle & inner ear structures
2) Enhancement of mid-high frequencies
--> Pinna effects
--> EAM Resonance
3) Improved Directional Hearing - hearing sounds in the environment depends greatly on differences in the time of arrival and intensity at the two ears as well as from the reflections from the pinna and concha into the ear canal.
Describe pinna effects in the enhancement of mid-high frequencies
Ridges & cavities on the pinna reflect sound waves with the reflected waves interacting with the incident waves; if the two waves are out of phase, negative interference will occur and intensity will decrease (Also, as the sound source increases in elevation, the dip in amplitude will increase in frequency).
Describe EAM resonance in the enhancement of mid-high frequencies.
Average resonance for average adult is 3430Hz. If their canal is shorter, resonance peak goes up. If canal is longer, resonance peak goes down.
What are the 2 cell types in the Organ of Corti?
1) Sensory cells - inner and outer hair cells
2) Supporting cells - Claudius, Hensens, Deiters, pillar, border, sulcus, and phalangeal cells
What is the role the olivocochlear bundle is believed to play?
1) Improving detection in noise
2) Protecting against noise damage
3) Expanding the dynamic range
4) Improving auditory attention
The primary auditory cortex is coated 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?
What membrane separates scala media from scala tympani?
List the major nuclei of the ascending auditory pathway
Auditory Cortex, Medial Geniculate Body, Inferior Colliculus, Superior Olivary Complex, Cochlear Nuclei
Describe the tectotirla membrane, including its connections.
The tectorial membrane is a gelatinous structure 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 cells on the lateral edge.
Which of the nuclei in the SOC is largest in humans?
Medial superior olive
What is the name of the structure which attaches the cochlear duct to the bony outer wall of the cochlea?
What happens when the inner hair cells are "activated"?
Neurotransmitters are released
Name the 3 chambers of the middle ear space.
1) Tympanic cavity
2) Epitympanic recess
3) Mastoid antrum
(MES = MET)
How many inner and outer hair cells are there in the human ear?
There are ~3500 inner hair cells and ~12,500 outer hair cells
What is the name of the structure that is seated on the basilar membrane?
Organ of Corti
What is the name of the muscle that is attached to the manubrium of the malleus?
What are the 2 cochlear resting potentials?
1) Intracellular potential - approximately -40mV for IHCs and -70mV for OHCs
2) Endocochlear potential - approximately +80mV - +100 mV
Which of the hair cells has a flask shape?
the inner hair cells
The auditory central nervous system is organized into two major paths, which are what?
1) Sound localization
2) 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?
The hair cell bodies are bathed in _________ while the stereocilia are bathed in _______.
The major descending projection of the central auditory system is what?
Olivocochlear system, which projects from the SOC to the cochlea
What is the name of the gelatinous structure that overlies the hair cells?
The structure which lies deep within the lateral sulcus and connects to both the primary auditory and association areas (and is believed to play a variety of roles in auditory processing) is know as what?
What are the landmarks of the auricle?
Helix, antihelix, tragus, antitragus, concha, lobule, triangular fossa
About how many primary auditory neurons are in the human ear? How many of these are afferent?
There are about 30,000 primary auditory neurons in the human ear about 95% of which are afferent
The two sections of the basilar membrane are known as what?
Describe the tonotopic organization of the auditory branch of CN8
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 organization 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?
Periphery nerve fibers - nerves
Periphery cell bodies - ganglion (ganglia)
CNS nerve fibers - tract
CNS cell bodies - nucleus (nuclei)
A neuron identified as EI is one that has what stimulation?
Excitatory input (EI) from the contralateral ear and inhibitory input from the ipsilateral ear.
What are the names of the 2 sections of the tympanic membrane?
1) Pars tensa
2) Pars flaccida
Describe the two different types of afferent primary auditory neurons.
1) Type I - make up 95% of afferent fibers; these are large, myelinated bipolar neurons (but not at the organ of cortisones) which contact the IHC
2) Type II - remaining 5% of afferent fibers, these are small, unmyelinated pseudo-monopolar neurons which contact the OHC
What happens when the medial olivocochlear bundle is stimulated?
When the MOC is stimulated, the activity of the outer hair cells is inhibited so that sensitivity and tuning are reduced
Which of the 3 nuclei of the inferior colliculus is responsive to auditory stimuli?
1) Central (ICC) - specific, core or lemniscal nucleus, which is responsive to sound
2) External Cortex & 3) Dorsal Cortex - the diffuse, belt or non-lemniscal nuclei which integrate the auditory and non-auditory inputs
What is the primary generator of the cochlear microphonic?
Outer hair cells
What is the name of the process in which the stereocilia of the hair cells are activated by the tectorial membrane?
Describe the ipsilateral arcs of the acoustic reflex.
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 psi stapedius
- In the other ipsilateral arc, primary neuron --> VCN --> secondary neuron --> ipsi SOC --> 3rd order neuron --> ipsi facial nerve nucleus --> 4th order neuron --> ipsi stapedius
Describe the contralateral arcs of the acoustic reflex.
- In one contralateral arc, primary neuron --> ipsi VCN --> secondary neuron --> ipsi SOC --> 3rd order neuron --> contralateral facial nerve nucleus --> 4th order --> contra stapedius
- Other contra - primary neuron --> ipsi VCN --> secondary neuron --> contra SOC --> 3rd order neuron --> contra facial nerve nucleus --> 4th order neuron --> contra stapedius
The breaks in the myelin sheath along the neuron's axon are known as what?
Nodes of Ranvier
Describe the composition and linkages of the stereocilia.
They are cross linked and tip linked. The tip links play an important role in the transduction process.
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
What is the name of the muscle that is attached to the stapes?
Name the cranial nerves
What are the voltages of the intracellular resting potentials?
IHC resting potential - -40mV
OHC resting potential - -70mV
What do auditory neuron studies tell us about the auditory system and hearing?
1) INTENSITY IS RATE CODED: (in addition to other ways)
2) AUDITORY NERVE FIBERS ARE TUNED IN FREQUENCY (have "best' frequencies)
3) NEURAL DISCHARGE PATTERNS ARE "PHASE-LOCKED" FOR FREQUENCIES BELOW ABOUT 4000-5000HZ
What is the position of the manubrium of the malleus when viewing the right ear through an otoscope?
Pointing toward 1 o'clock
What are the major cues to localization in the horizontal plane?
Frequencies below 1900Hz are diffracted, so cue is difference in interaural time of arrival. For frequencies above 1900Hz, cue is interaural level difference
Describe cranial nerve VIII
CN VIII is made up of 2 branches - 1 from vestibular and 1 from 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 window?
What happens when the stereocilia of the hair cells are sheared?
Ions flow into the cells
Neurons may be classified in three groups. These are:
Damage to the synaptic junction between the hair cells and the auditory nerve results in a condition known as what?
The condition is known as synaptopathy or "hidden hearing loss" because it does not elevate thresholds, but rather is associated with problems on more complex auditory tasks such as speech recognition in noise
Name the 3 channels of the inner ear
1) Scala vestibuli
2) Scala media
3) Scala tympani
What is the resonant frequency of the middle ear?
active and passive processes in cochlea
depolarization and hyperpolarization
cell types and functions in cns
roles of the relevant CNs
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