Lesson 7: Cranial Nerve VIII, Auditory Flashcards Preview

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Flashcards in Lesson 7: Cranial Nerve VIII, Auditory Deck (124):
1

Inner ear structure and function:
Bony Labyrinth:
Hearing?
Angular Acceleration Head Rotation?
Linear Acceleration Gravity?

Cochlea
Semicircular Canals Vestibule

2

Inner ear structure and function:
Membranous Labyrinth:
Hearing?
Angular Acceleration Head Rotation?
Linear Acceleration Gravity?

Cochlear Duct Semicircular Ducts
Saccule, Utricle

3

Inner ear structure and function:
Receptor:
Hearing?
Angular Acceleration Head Rotation?
Linear Acceleration Gravity?

Organ of Corti
Crista Ampularis
Macula

4

Inner ear structure and function:
Gel:
Hearing?
Angular Acceleration Head Rotation?
Linear Acceleration Gravity?

Tectorial Membrane Cupula
Otolithic Membrane

5

Pathway of Central Processing of Hearing: Where do the synapses occur in the ascending auditory pathways?

First synapse: occurs in the pons in the cochlear nuclei complex (dorsal or ventral cochlear nuclei).
Then some fibers cross to synapse in superior olivary nucleus or the nucleus of the trapezoid body. Information ascends in both crossed and uncrossed pathways.

6

Pathway of Central Processing of Hearing:
What integration happens at the midbrain level?

Integration with proprioception information from muscles in the neck and visual signals. This ties together information about visual and hearing cues with neck movements

7

Auditory Reflexes: Where are postural responses to sound (head and neck movements) communicated?

Communicated at the midbrain at the level of the inferior colliculus

8

What is the structure in the brainstem that responds to hearing?

Inferior colliculus

9

For conscious appreciation of sound, where does information travel and terminate?

Info continues to the medial geniculate body and finally to Heschl’s gyrus in the auditory cortex (areas 41 and 42 of the temporal lobe) for conscious appreciation of sound.

10

Which structures figure out where a sound is coming from, based on the sound's relative arrival time?

The superior olivary nucleus and then the auditory cortex “figures out” the arrival time of all these signals and (based on which ear heard the sound first)

11

Why is it that some sound signals have to cross and ascend to the auditory cortex vs. just ascending on the same side?

(Sound from the left) It will reach the left cochlea first, later the right cochlea. There is a delay on the right due to the difference in distance between ears from the sound source (and difference in intensity due to distance)

12

What is the result of damage to the cochlea on one side?

Localization of sound will be difficult

13

What is the results of the auditory cortex being damaged on one side?

There is both crossed and uncrossed information from both (intact) ears arriving at the one intact cortex and localization of sound is still possible.
Sound will still arrive at the intact cortex from both ears with the qualities of intensity and frequency being controlled by the middle and inner ear
Sound waves that arrive at both ears at the same intensity will be heard as being only slightly less loud by the ear contralateral to the cortical damage.

14

Will cortical damage change the timing of signals travelling to Heschl's Gyrus?

Cortical damage won’t change the timing of the signals travelling to Heschl’s gyrus, such that direction is still perceived accurately if the signal is sufficiently loud

15

Auditory Radiation: Where does auditory info leave, travel and terminate?

Info leaves the medial geniculate body and travels in the sublenticular limb of the internal capsule via the auditory radiation to the auditory cortex

16

What happens after the info from the cochlear component of the auditory nerve leaves the cochlea and joins with the vestibular component?

It travels through the petrous portion of the temporal bone.
It exits the petrous portion of the temporal bone of the skull through the internal auditory meatus entering the posterior cranial fossa traveling with the facial nerve
Together they enter/leave the brainstem at the juncture between the pons and medulla (ponto-medullary, ponto-cerebellar, or cerebellar-pontine junctions).

17

Where would a lesion be if a patient presents with damage to both the facial nerve and the auditory nerve?

Is anatomical evidence that the lesion is likely to be where the two nerves travel together
Damage is most likely in peripheral nerves and may be quite close to the brainstem that the functions of the entire facial nerve and probably auditory nerve would be involved,

18

Components of the Vestibular System: what is the cellular mechanism of the cupula?

(A gel) disturbed by motion of fluid in the ducts (semicircular canals), ampula or saccule, thereby activating hair cells and transduction of physical to electrical energy primary neurons who have their cell body in the vestibular ganglion and synapse in the vestibular nuclei in the brainstem

19

Testing the Vestibular System: How does Doll's Eye work?
Is it tested on conscious or unconscious people?

Eyes respond to the position of the head by correcting for changes in head position. This reflex operates to keep eyes focused on the object as the head turns (opposite of scanning)
- The test it done on an unconscious patient assessed in their resting position

20

Testing the Vestibular System: How is Doll's Eye tested?
Reflex Absent/Present

-If the vestibular system or the connection between the vestibular system and the medial longitudinal fasciculus (MLF) in the brainstem is SEVERELY damaged
Doll’s Eye is absent: when the head is turned by the examiner to the left or right, the eyes will remain in the same position as the head.
If this area is intact, the eyes will move in opposite direction to the head movement giving the appearance of them remaining straight forward looking.

21

Testing the Vestibular System: What is the Caloric Test?

-Water (either warm or cool) is placed in the external ear. This alters the temperature of the middle ear and by convection induces a current in the endolymph within the semicircular canals (the horizontal canal predominantly)
this technique is done to simulate head rotation without actually requiring the patient to actually move. The eyes are closely monitored for nystagmus, which is the normal reflexive response indicating that the vestibular circuitry is intact on the test side.

22

Testing the Vestibular System: Caloric Test - why us this technique done?
What is looked for in the eyes?

To simulate head rotation without actually requiring the patient to actually move. The eyes are closely monitored for nystagmus, which is the normal reflexive response indicating that the vestibular circuitry is intact on the test side.

23

Testing the Vestibular System: Caloric Test - What happens with warm water/cold water?
How is nystagmus named?

-Warm water: in the canals causes the eyes to drift AWAY from the tested side, then snap back quickly to the tested side, this repeats: drift away -- > snap back
-Cold water: Cold water in the right ear would cause the eyes to drift to the right and then snap left; hence the vestibular nystagmus is to the left.

24

Testing the Vestibular System: Caloric Test - How is nystagmus named? (+example)
What acronym can be used?

The nystagmus is named for the side the eyes snap back towards.
For instance, when testing the right ear with warm water, eyes drift to the left and vestibular nystagmus (snap back) is to the right.

COWS (cold-opposite, warm-same side).

25

Connections of the Vestibular System: What is the function of the vestibular tract?

Constant input to the limbs to keep supporting reflex active produces extension of the upper and lower limbs

26

Connections of the Vestibular System: What is the fubction of the MLF?

Medial longitudinal fasciculus to coordinate eye muscle with vestibular input.

27

Connections of the Vestibular System: What is the function of the reticular system?

To keep constant input to the alertness centre (consciousness).

28

Where do the cochlear and vestibular nuclei span?

The cochlear and vestibular nuclei span the ponto-medullary junction.

29

Olfactory Nerve: Where are the first and second order cell nuclei?
What is the function of the nerve?

First Order: neuroepithelial olfactory cells in nasal mucosa
Second Order: olfactory bulb
Function: Smell

30

Optic Nerve: Where are the cell nuclei?
What is the function of the nerve?

Ganglion cells in retina Function: Vision

31

Oculomotor Nerve: Where are the cell nuclei? (3)
What are the functions of the nerve? (3)

Nuclei: Oculomotor nucleus in upper midbrain tegmentum
Edinger-Westphal nucleus in midbrain tegmentum
Preganglionic parasympathetic projections to ciliary ganglion

32

Trochlear Nerve: Where are the cell nuclei?
What is the function of the nerve?

Trochlear nucleus in midbrain tegmentum
Function: Eye movements: innervates contralateral superior oblique muscles

33

Trigeminal Nerve: Where are the First and Second Order nuclei, and others?
What is the function of the nerve?

First order: trigeminal (semilunar) ganglion
Second order: primary sensory (pons), descending spinal nucleus (pons, medulla, and upper cervical levels
Mesencephalic nucleus (midbrain)
Trigeminal motor nucleus in pons

34

Abducens Nerve: Where are the nuclei?
What is the function of the nerve?

Abducens nucleus in tegmentum of pons
Function: Eye movements: innervates ipsilateral lateral rectus muscle

35

Facial Nerve: Where are the nuclei, First and Second-Order, other?
What is the function of the nerve?

Superior sailvatory nucleus: preganglionic parasympathetic to ganglia associated with oral, lacrimal, and nasal glands
First order: geniculate ganglion
Second order: nucleus solitarius
Facial motor complex in lateral pons

36

What is the function of the trigeminal nerve?

Function: Receives pain and touch sensations from skin and muscles in face, orbit, nose, mouth, forehead, teeth, meninges, anterior two-thirds of tongue, external auditory meatus, and external surface of tympanic membrane
Proprioception from jaw
Innervates muscles of mastication (masseter internal and external pterygoid and temporal), mylohyoid, anterior belly of digastric, tensor velum palatini, and tensor tympani muscles

37

What are the functions of the oculomotor nerve?

Eye movements: controls all eye muscles except lateral rectus and superior oblique muscles
Regulates eyelid elevation (levator palpebrae superioris)
Reflexive constriction of pupil and accommodation of lens for near vision

38

What is the function of the facial nerve?

Parasympathetic regulation of secretion from nasal, palatal, lacrimal, submaxillary, and sublingual glands and mucous membrane of nasopharynx
Mediates gustatory sensation from taste buds in anterior two-thirds of tongue
Innervates muscles of facial expression and platysma, extrinsic and intrinsic ear muscles, and stapedius muscle

39

Vestibulocochlear Nerve: Where are the nuclei, First and Second-Order, other?

First order: superior and inferior vestibular ganglia
Second order: vestibular nuclei in medulla and pons

First order: spiral ganglion
Second order: cochlear nuclei in medulla

40

Vestibulocochlear Nerve: What is the function of the nerve?

Maintains equilibrium and head orientation in space

Mediates audition

41

Glossopharyngeal Nerve: What are the nuclei - First and Second-Order and other?

First order: inferior ganglion
Second order: nucleus solitarius

Inferior salivatory nucleus: preganglionic to otic ganglion

First order: inferior ganglion
Second order: nucleus solitarius
Nucleus accumbens

42

What is the function of the glossopharyngeal nerve?

Mediates general sensation from palate, posterior third of tongue, oral pharynx, middle ear, eustachian tube (ear ache), and carotid sinus
Parasympathetic regulation of secretion from parotid gland and oral pharyngeal mucosal glands
Mediates taste sensation from poertior third of tongue and oral pharynx
Contributes to swallowing by controlling stylopharyngeus muscle

43

Vagus Nerve: Where are the nuclei - First and Second Order?

First order: inferior ganglion
Second order: nucleus solitarus

Dorsal motor nucleus: preganglionic parasympathetic innervation

First order: inferior ganglion
Second order: nucleus solitarius

Nucleus ambiguus

44

What is the function of the vagus nerve?

Receives general sensation from pharynx, larynx, thorax, abdomen, carotid body, and aortic body
Regulates nausea, oxygen intake, and lung inflation
Innervates glands and muscles in heart, blood vessels, trachea, bronchi, esophagus, stomach and intestine
Mediates taste sensation from sensory buds in epiglottis and pharynx, and laryngeal pharynx
Controls muscles of larynx, pharynx, soft palate for phonation, deglutition, and resonance

45

Spinal Accessory: Where are the nuclei?
What is the function of the nerve?

Spinal accessory nucleus in C1-C5 ventral horns Function: Controls head and shoulders by innervating trapezius and sternocleidomastoid muscles

46

Hypoglossal Nerve: Where are the nuclei?
What is the function of the nerve?

Hypoglossal nucleus in medulla
Function: Controls tongue movement by regulating intrinsic and most extrinsic muscles

47

Which 3 cranial nerve motor nuclei are in the midbrain tegmentum?

- Edinger-Westphal nucleus (oculomotor nerve)
- Oculomotor nucleus (oculomotor nerve)
- Trochlear nucleus (trochlear nerve)

48

What are the 6 major cranial nerve nuclei in the pontine tegmentum of the pons?

- 3 sensory nuclei of the trigeminal nerve: primary sensory nucleus, spinal trigeminal nucleus, and mesencephalic nucleus
- Primary/Spinal Trigeminal
- Mesencephalic
- Trigeminal motor
- Abducens motor

49

What are the 9 major nuclei of the medulla?

Cochlear and vestibular nuclear complex
Salivary nucleus
Dorsal motor nucleus
Hypoglossal nucleus
Nucleus solitarius
Spinal trigeminal nucleus
Inferior olivary nucleus
Nucleus ambiguus

50

Motor or Efferent Pathways: Where do cranial nerve nuclei receive motor projections?
Where do the fibres arise, and where do they descend?
Where do the fibres synapse?

Receive motor projections from the corticonuclear fibres.
The fibres arise from the motor cells (UMN) in the lower part of the precentral cortex
Descend through the genu of the internal capsule Synapse on the motor cranial nerve nuclei (LMN) in the brainstem

51

Innervation Pattern: Which muscles receive only contralateral innervation ?

Lower facial muscles, sternocleidomastoid and trapezius muscles, tongue muscles, and ocular muscles and abducens

52

How does the innervation of the ocular muscles work?

Left frontal cortex activated = activation of right pontine gaze center, and activation of right abducens = contraction of right lateral rectus and left medial rectus muscles = both eyes turn to the right

53

How does the auditory system begin?

Begins as sound waves strike the tympanic membrane – vibration converts pressure waves into mechanical energy, setting middle-ear ossicles into motion

54

Auditory System: How is mechanical energy transformed in the inner ear and what is the cascade of structures and impulses into the brain?

Mechanical energy further transformed into hydraulic energy in cochlear fluid of the inner ear ->patterned hydraulic waves stimulate cochlear hair cells – send coded impulses through the fibers of the vestibulocochlear nerve to the cochlear nuclear complex in the brainstem

55

Auditory System: At the cochlear complex, what kind and where does it send impulses?

Cochlear complex nuclei transmit nerve impulses to multiple synaptic points in the brainstem and the thalamus before projecting to the primary auditory cortex

56

Auditory System: Where do the auditory impulses travel from the primary auditory cortex and terminate?

Auditory impulses -> primary auditory cortex -> superior surface of the temporal lobe in Heschl gyri -> Wernicke Area in left hemisphere

57

What is Frequency? How is it related to pitch?

Frequency = speed of particles vibration (cycles per second – Hertz);
Low frequency = low pitch High frequency = high pitch

58

How is pitch measured? What is it?

Measured in decibels dB = log of the ratio between the measure sound pressure (px) at the tympanic membrane and a well defined reference sound pressure (pr).

59

Sound Pressure Level: What is the equation?
What level SPL is required to make a 1000Hz sound just audible to the human ear?

in dB = SPL (dB) – 20 log Px/pr
SPL required to make a 1000 Hz sound just audible to the human ear

60

Transmission of Sound:
What are the structures of the External Ear and what are their functions?

Pinna, external auditory meatus, tympanic membrane: contribute to sound detection by collecting and channeling the collected sound waves in auditory meatus to the tympanic membrane.
Pinna and canal enhance peak resonance of sound, help with sound localization

61

Transmission of Sound: What are the structures of the Middle ear? Is it air of fluid filled?

Air filled
Ossicles - malleus, incus, and stapes: which connect the tympanic membrane to the oval window of the inner ear
Eustachian tube: runs from middle ear to nasopharnyx, ventilates middle ear by equaling middle-ear pressure with atmospheric pressure
Tensor tympani: inserts into malleus and participates in restricting ossicular movements in response to louder sounds, specifically noises
Stapedius: inserts into stapes and contracts to restrict stapes movement in response to sounds louder than 70-80 dB

62

Transmission of Sound: What is the mechanism of ....

Regulates energy transmission to inner ear by stiffness of ossicles to make up difference between air and fluid, and tympanic membrane and oval window -> reduces movement of tympanic membrane and increases its force on the cochlear oval window to ensures an optimal transmission of sound (restricts the motion speed)

63

Transmission of Sound: What are the structures of the inner ear? What do they do?

Dual-functional mechanism for serving the special sensory modalities of audition and equilibrium which are served by the membranous labyrinth ducts
Contains the fluid-filled sacule, utricle, semicircular ducts, and the cochlear dicut = vestibular apparatus = mediate equilibrium
Cochlear duct - scala media = hearing and other special sensory functions

64

Cochlear Structure: What are the 3 fluid-filled scalae?
(Which compartment, where do they live, what are they filled with?)

Scala Vestibuli: upper compartment; follow inner contour of cochlear duct and joins scala tympani at the ape of the cochlea through the helicotrema; filled with perilymph
Scala Tympani and Media: lower compartment; media ends near the cochlear apex, between the tympani and vestibule; tympani filled with perilymph, media filled with endolymph

65

In the Scala Media of the cochlea, what is the structure of the sensory hair cells, cilia?
What are the IHC and OHC innervated by?

Contains organ of Corti with sensory hair cells – arranged in 3 rows of OHC, and 1 row of IHC, which run along the basilar membrane.
More OHC cilia than IHC.
- Taller cilia of HC project over entire organ of Corti
- IHC are innervated by cochlear nerve endings, OHC are connected to projections from descending auditory pathways

66

What is the function of the cochlea?

Absorbs mechanical energy and transfers sound vibrations into neural impulses

67

Cochlear Function: What is the function of the basilar membrane?
What happens as the membrane is displaced at the base?

- Responds to transmitted pressure in cochlear perilymph by its displacement.
- Has higher frequency representation in the base (narrower than apex) the site of low frequencies.
- Deformation moves toward the apex of the cochlea as a traveling wave – its velocity slows, amplitude increases toward apex.

68

Cochlear Function: When the membrane is displaced, what happens to the frequency?
Where are the hair cells most stimulated?

Frequency of stimulus decreases – peak amplitude of wave moves toward helicotrema. Multiple peaks along the basilar membrane – hair cells most stimulated at the point of the maximum peaks

69

Cochlear Function: What is the mechanism that occurs when the membrane moves?

Produces mechanical displacement of cilia relative to tectorial membrane. Bend the apical ends of the hair cells = increased cilia permeability to K+.
Inward movement of ions leads to local depolarization of hair cell = synaptic vesicles release a NT in the synaptic cleft between hair cells and cochlear nerve fibers.
⇒ depolarizes afferent cochlear nerve terminals, and generated action potentials travel to brainstem through fibers of vestibulocochlear nerve

70

Electrical Transmission in the inner ear: In the basilar membrane, what cascade of events happens when it moves against the tectorial membrane?

Action potential (ions involved, structures involved)

Where does the action potential travel and terminate in the brain?

Basilar membrane moves against tectorial membrane, deformation of the stereocilia of hair cell bundle increases potassium ion permeability and opens K+ sensitive pores in the tips of cilia
- Deformation of receptive ends in cochlea cells opens ion-specific channels, allowing the movement of potassium into cell bodies through cilia in scala media – depolarized opens the calcium channels, moving into the cell – causes synaptic vesicles at the base of the cell to release glutamate in synaptic space
- Action potential discharges that are generated in the nerve terminus travel through peripheral and central fibers of CN VIII to the cochlear nuclear complex located at the pontomedullary junction

71

Retrocochlear Auditory Mechanism: Where does it transmit signals?
Where do the hair cells transmit impulses?

Transmits signals from the hair cells in the organ of Corti to the brainstem cochlear nuclear complex
- Hair cells transmit nerve impulses to peripheral axons of the unipolar spiral ganglia

72

Retrocochlear Auditory Mechanism: Spiral Ganglion Cells
What do these cells form and where do they pass in the brain?
Where do these cells synapse?

Central process of spiral ganglion cells form the acoustic branch of the vestibulocochlear nerve and pass through the internal auditory meatus, a canal in the petrous portion of the temporal bone.
- The afferent axons synapse in the cochlear nuclear complex

73

Central Auditory Pathways: Where do they extend from, where do the relay their nuclei, and where do they synapse?

Extends from the cochlear nuclear complex and all its relay nuclei up to and including the primary auditory cortex; has multiple synapses between cochlear nuclei and thalamus

74

Which complex are these structures a part of?
Cochlear nuclei, superior olivary nuclei, lateral lemniscus, inferior colliculus, brachium of inferior colliculus, medial geniculate body, auditory radiations, and primary auditory cortex in transverse gyri of Heschl

Central Auditory Pathway

75

In the central auditory pathway, is information preserved tonotopically?

Preserving information – retention of tonotopic representation from cochlear hair cells to primary auditory cortex.

76

Cochlear Nuclear Complex: Where do the vestibulocochlear nerves enter the brainstem and where do they terminate?

Enter the brainstem at the pontomedullary junction and terminate in the cochlear nuclear complex

77

Cochlear Nuclear Complex: What are the two divisions of the complex?

Dorsal: lies dorsolateral to the restiform body
Ventral cochlear nucleus: is ventral and lateral to the restiform body

78

Cochlear Nuclear Complex: where do the fibres from the apex/base of the cochlea terminate?

Apex of cochlea (low-frequency info), terminate at superficial layers of cochlear nucleus;
Base of cochlea (high-frequency info) penetrate deeper in the cochlear nuclear complex

79

Cochlear Nuclear Projections: are projections sent to the ipsilateral or the contralateral ascending auditory pathways?

Send multiple projections to both the ipsilateral and contralateral ascending auditory pathways

80

Cochlear Nuclear Projections: What are the three bundles that project across the midline?

dorsal acoustic stria, intermedia stria, trapezoid body

81

Cochlear Nuclear Projections: Where do cells of the trapezoid body, intermedia stria, and dorsal acoustic stria terminate?

Trapezoid: Terminate in the superior olivary nucleus
Intermedia: Project to ipsilateral and/or contralateral superior olivary nucleus
Dorsal: terminate in the contralateral lateral lemniscus

82

What does the superior olivary nucleus do?

Receives auditory inputs from both the ipsilateral and contralateral cochlear nuclei

83

What important cells does the superior olivary nucleus have?

Binaural cells: equipped to calculate differences in the time and intensity of auditory stimuli from both ears.

84

What two places does the superior olivary nucleus receive projections?

Medial dendrite receives projections from the contralateral cochlear nuclei
Lateral dendrite receives input from the ipsilateral cochlear nuclei.

85

What is the function of the lateral lemniscus?

Primary ascending pathway; Receives crossed and uncrossed projections from the dorsal, ventral, and intermediate striae

86

Inferior Colliculus: What does it do?

Respond to complex patterns of auditory stimuli;
Provides an organism with a 3-D neurologic map of the external environment

87

Inferior Colliculus: Where does it recieve projections from?

Lateral lemniscus fibers synapse on the nuclei of the IC
Ascending auditory signal send collateral information into the IC

88

Inferior Colliculus: Where does it send projections?

-Primary output of the IC is to the thalamus, as its projections travel through the brachium to the MGB

Projects fibers into the deep layers of the superior colliculus where the common output for the visual and auditory startle reflexes

89

Medial Geniculate Body: What does it do?

Is the thalamic relay nucleus for the transmission of auditory information

90

Medial Geniculate Body: Where does it receive projections from?
Where does it send projections?
Where do the projections terminate?

It receives tonotopic input from the ipsilateral IC
Project to the lenticular portion of the internal capsule.
Terminate in the ipsilateral primary auditory cortex, the gyri of Heschl, in the superior temporal lobe

91

Primary and Auditory Association Cortex: Where is it located?
Where does it receive projections from?

Located in the transversely oriented gyri of Heschl
-Receives impulses through crossed and uncrossed fibers from both ears

92

Primary and Auditory Association Cortex: What is Wernicke's Area?

It is concerned with the comprehension of spoken language, which involves recognizing language stimuli, interpreting their meanings, and recognizing social/paralinguistic properties of language with respect to previous memories and linguistic experiences and knowledge.

93

What are the three pathways for auditory reflexes?

1. Includes the projections from the IC to the superior colliculus and tectum, integrating the auditory and visual systems and controlling extraocular movements
2. From superior olivary nucleus to the medial longitudinal fissure projects to the nuclei of the nerves: oculomotor (CN III), trochlear (CN IV), abducens (CN VI). Regulates directional ocular movements in response to auditory stimuli
3. Includes the auditory projections to the vestibular nuclear complex and participates in equilibrium

94

Where do the inner ear cochlear mechanism, semicircular canals of the vestibular mechanism, and spiral ganglia and their central and peripheral processes receive their vascular supply?

Basilar artery, in particular the internal auditory artery, a branch of the anterior inferior cerebellar artery (AICA)

95

Blood supply to the primary and secondary auditory cortex flows through which structure?

Branches of the middle cerebral artery

96

Bilateral Auditory Representation: Would a lesion in the central auditory pathway result in complete hearing loss?

Extending from the pons to the auditory cortex would not result in complete hearing loss involving either of the ears – causes only a mild loss of hearing

97

Bilateral Auditory Representation: Which structures contribute to the bilaterality of cortical auditory representation?

The cochlear nuclei, lateral lemniscus, and IC

98

Is tonotopic representation maintained at the cochlear level in the central auditory pathway?

Discrete tonal representation at the cochlear level is maintained throughout the central auditory pathway.

99

What is interaural time delay?

When each ear receives a particular sound but at different time - the difference

100

What does the process of lateral inhibition do in the descending auditory pathways?

Provide feedback circuits to refine the perception of pitch and loudness and to sharpen the reception of specific frequencies

101

What are the pathologies and symptoms of conductive hearing loss?

Middle ear pathologies affect sound transmission to the cochlea which is characterized by fluctuating hearing loss; good word-speech recognition ability; softly spoken speech; impaired auditory reflex; and an air-bone gap

102

What is a pathologic growth of bone near the oval window impedes the movement of the stapes?

Osterosclerosis

103

What is an accumulation of fluid of idle ear causes the Eustachian tube to malfunction?

Otis Media

104

What are the pathologies and symptoms of sensorineural hearing loss?

Associated with damage to the cochlear hair cells and/or the auditory nerve
- Characterized by difficulty in understanding speech, particularly in the noise, and frequently by tinnitus. Patients usually speak loudly as a result

105

What disease is: associated with edema and excessive endolymphic pressure in the membranous labyrinth, marked by progressive and fluctuating hearing loss, sensation of ringing in the ears and vertigo?

Meniere Disease

106

Where and what vestibular schwannoma/acoustic neuroma associated with?

Located at the cerebellopontine angle and are clinically associated with hearing impairment and disequilibrium

107

What type of impairment: - Includes the lower, upper brainstem and primary auditory cortex. Dysfunction feature is the near-normal sensitivity/thresholds to auditory?

Central Auditory Impairment

108

What would a lesion involving the superior olivary nucleus has a minimal effect on hearing sensitivity, but is has a profound effect on the ability to identify and localize the source of sound, an ability of summating temporal information received from both ears?

Lower brainstem symptoms

109

What would pathological involvement affecting the transmission of auditory signals and the integration of audition with visual-motor functions for reflexive responses. Also has implications for the metacognition of self-awareness in 3D space?

Upper brainstem symptoms

110

What are the resulting behaviours of a unilateral cortical lesion?

Usually exhibit near normal hearing thresholds, display an impaired ability to perceive and discriminate speech

111

What are the resulting behaviours of a bilateral cortical lesion?

Both hearing sensitivity and speech perception are profoundly impaired.

112

What is acoustic aphasia?

Marked by an impaired discrimination of speech sounds

113

What is a severe loss of language comprehension, through speech production, naming, reading and writing are spared. Associated pathology involves a bilateral temporal lesion?

Word deafness

114

Tuning Fork Test: What is the process of the Rinne test?
What would a person hear with normal hearing or SNHL?
What would a person hear with CHL?

-Stem of a vibrating tuning fork is placed on the mastoid process and patient asked to listen to the tone. When the tone from the fork is no longer heard by the patient, the fork is placed in front of the ear to determine if the patient can still hear the sound.
-Normal hearing or SNHL: should hear the tone longer by air conduction than by bone conduction (positive Rinne).
CHL: hears the sounds longer by bone conduction (negative Rinne)

115

Tuning Fork Test: What is the process of the Weber test?
What would a person hear with normal hearing or bilaterally symmetrical hearing loss?
What would a person hear with a unilateral CHL?
What would a person hear with a unilateral SNHL?

- A vibrating tuning fork is placed on the scalp at vertex and the patient is asked to lateralize the sound by indicating whether the tone is louder in one ear
Normal hearing or bilaterally symmetrical hearing loss: the sound is sensed at the midline.
Unilateral CHL: hear the sounds in the affected ear.
Unilateral SNHL: hear the sounds mainly in the unaffected ear

116

Pure Tone Audiometry: What does it establish?
How is hearing tested?
What does hearing loss refer to?
What happens in CHL?

- Establish threshold of hearing across the frequency range that is most important for human communication. Pure tone audiometer generates pure tones at various frequencies and intensities
- Hearing is tested by determining air- and bone-conduction thresholds to each frequency
- Hearing loss: increase in intensity above the normal sensitivity require to reach the threshold.
CHL: the threshold for bone conduction is normal and better than that for air, also called air-bone gap

117

What does tympanometry measure?

Measures the compliance of the tympanic membrane and middle-ear pressure under the conditions of changing air pressure in the external auditory meatus

118

Otoacoustic Emission:
What do cochlear OHCs do?
How is hearing loss determined?

-Cochlear OHCs in normally hearing individuals expand and contract in response to sound stimulation. This movement produces minute pressure waves that are transmitted through the cochlear fluids and can be recorded in the external ear canal.
-Absence of minute clinical signal indicates dysfunction of the OHCs, thus suggesting a hearing loss

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What does auditory brainstem response audiometry measure?
What do the waveforms tell you?

Measures neuronal activity from the brainstem auditory pathway within 10ms after the onset of controlled stimuli, such as clicks.
Within the period, 5 vertex positive wave peaks are identified from the event-based electrical activity recorded from scalp electrodes
- Each waveform generated at a different anatomic point in auditory pathway. By taking into consideration the altered interpeak latency or changes in the peaks of amplitude, one can identify potential lesion sites in the vestibulocochlear nerve or brainstem

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What structures regulate dynamic equilibrium?

- Hair cells of the cristae in the maculae of the semicircular ducts regulate dynamic equilibrium.

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What do the sensory cells in the semicircular ducts response to?
How does the mechanism works?

Respond to angular and rotational head movements
-When receptors in the duct of one side are excited, receptors in the corresponding semicircular duct of the opposite side are simultaneously inhibited
-On rotation of the head, the moving endolymph in the canal deforms the cristae. Deformation of the hair cells generated action potentials, which travel to the brainstem

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When does neuronal firing increase/decrease in the semicircular ducts?

Frequency of firing increases when the crista bends toward the utricle, and the rate decreases when the crista bends away from the utricle

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What do the utricle and saccule do?

Monitors and maintains a balanced position of the head and body in space against gravity while standing and during straight-line head movements

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What is the action potential mechanism for the saccule and utricle?

Movement of the otolithic membrane generates action potentials that are transmitted to the brainstem
- The orientation of the maculae to the direction of the gravity force determines the pattern of action potentials. This leads to immediate muscle tone adjustment, which is needed for the maintenance of equilibrium