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BRAIN AND BEHAVIOUR > Hearing > Flashcards

Hearing Flashcards

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The Brain flashcards
1
Q

Name the 4 divisions of the auditory system

A

Outer ear, middle ear, inner ear and central auditory nervous system

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2
Q

What is the overall function of the outer ear?

A

Takes in air vibrations and works to protect the air alongside localising and amplifying sound

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3
Q

What is the overall function of the middle ear?

A

Takes in mechanical vibration and is involved in impedance matching, pressure equalisation and inner ear stimulation

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4
Q

What is the overall function of the inner ear?

A

It takes in mechanical, hydrodynamic and electrochemical stimulation and is involved in sound filtering and signal transduction

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5
Q

What is the overall function of the central auditory nervous system?

A

It takes in electrochemical stimulation and is involved in information processing

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6
Q

What is involved in impedance matching?

A

It involves the Eustachian tube where the differences in area between the eardrum (tympanic membrane) and the oval window are compensated for, between the air and cochlear fluid

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7
Q

Which component of the inner ear is involved in amplification of sound signals?

A

Outer hair cells

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8
Q

How is transduction facilitated in the inner ear?

A

The mechanical signals are converted into electrical signals by the opening (depolarisation) or closing (hyperpolarisation) of potassium channels, depending on the direction of hair movement

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9
Q

Describe the flow of sound/vibration in the inner ear

A

Stapes (bone) –> oval window –>perilymphatic fluid in the cochlear (vibrates) –> round window

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10
Q

What is the difference in composition between the endolymph and the perilymph?

A

Endolymph is high in potassium whereas perilymph is high in sodium

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11
Q

How many canals are there in the cochlea?

A

Three

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12
Q

Name the three canals within the cochlea

A

Scala vestibuli, Scala tympani and Scala media

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13
Q

What type of fluid is in the scala vestibuli and scala tympani?

A

Perilymph (high in sodium)

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14
Q

What type of fluid is in the scala media?

A

Endolymph, as it contains the organ of Conti

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15
Q

Where is the Organ of Conti located?

A

In the scala media of the cochlea

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16
Q

Describe the structure of the organ of Conti

A

There is the upper membrane (tectorial membrane) and the lower (basilar membrane) and there are hair cells inbetween these

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17
Q

Describe the structure and function of inner hair cells in the organ of Conti

A

The inner hair cells are the inner one layer of cells in the organ of Conti and these cells form 95% of the cochlear nerve (auditory nerve) and are involved in auditory discrimination

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18
Q

Describe the structure and function of outer hair cells

A

These cells consist of the 3 outer rows (nearer to basal side) which have cilia embedded in the tectorial membrane and are involved in frequency tuning (amplify the basilar membrane vibrations, so enhance sensitivity and frequency selection)

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19
Q

How do we differentiate sounds at different frequencies?

A

Movement from vibration in perilymph (cochlea) reaches organ of Conti –> vibration of basilar and tectorial membranes which stimulates certain hair cells –> these cells depolarise and stimulate cochlear aspect of CN VIII, and brain will relay pitch based on the hair cell that is stimulated

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20
Q

How do we localise sound (direction)?

A

We use timing and loudness - the superior olivary nucleus uses interaural time differences and interaural level differences in order to localise sound cues

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21
Q

Which nucleus is involved in the localisation of sound direction?

A

Superior olivary nucleus

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22
Q

What is meant by pitch/frequency?

A

The number of oscillations per second

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23
Q

What is meant by intensity/loudness?

A

Height of the sound wave

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24
Q

What is loudness/intensity measured in?

A

Decibels (dB)

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25
Q

Name the 5 main brain structures involved in the auditory pathway

A

Cochlear nucleus, superior olivary nucleus, inferior colliculus, medial geniculate nucleus and primary auditory cortex

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26
Q

Describe the auditory pathway

A

The cochlear primary nerve afferent travels through internal auditory meatus to cochlear nucleus –> some transmitted to superior olivary nucleus –> rest transmitted to inferior colliculus –> transmitted to medial geniculate nucleus –> primary auditory cortex

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27
Q

Where is the superior olivary nucleus found, and what is its function?

A

In the pons and it is involved in spatial localisation

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28
Q

Where is the cochlear nucleus located, and what is its function?

A

It’s located in the medulla, and the ventral aspect is involved in intensity and location of sound whereas the dorsal aspect is involved in pitch and quality

29
Q

Where is the inferior colliculus located?

A

Midbrain

30
Q

Where is the medial geniculate nucleus located?

A

Midbrain

31
Q

Where is the primary auditory cortex located?

A

Cerebrum

32
Q

Which limbic areas are activated by sound?

A

Medial pre-frontal cortex, nucleus accumbens, orbitofrontal, amygdala and midbrain

33
Q

Where does CN VIII get it’s auditory information from?

A

Cochlea

34
Q

Where does CN VIII get its vestibular information from?

A

Semicircular canals, utricle and saccule

35
Q

Describe the ventral cochlear nucleus

A

This is very fast and precise and projections go to the superior olivary nucleus and stellate cells code intensity whilst bushy cells encode timing

36
Q

Describe the dorsal cochlear nucleus

A

Complex responses are facilitated here, where axons project to the lateral lemniscus and encode quality of sound and analyse pitch

37
Q

What is meant by conduction deafness?

A

When air conduction is impeded such as is the case with damage to the ear itself

38
Q

What is meant by sensorimotor/nerve deafness?

A

A type of deafness whereby there is nerve damage (brain or cochlear nerve etc.) or if you damage the cochlea itself

39
Q

Describe how you would conduct Rinne’s test

A

Place a vibrating tuning fork on the mastoid process (just behind the ear) and then when they can no longer hear it put it next to their ear and see if they can hear it now

40
Q

What is a normal/non-pathological result for Rinne’s test?

A

Sound is heard louder and longer by air conduction (>15 seconds)

41
Q

What would suggest conduction deafness in Rinne’s test?

A

If the bone conduction is better than the air conduction on the affected side

42
Q

What would suggest sensorimotor deafness in Rinne’s test?

A

If air conduction is better than bone conduction in the affected ear but sound is loudest in the unaffected ear

43
Q

Name the two major tests used to diagnose deafness

A

Rinne’s test and Weber’s test

44
Q

Describe how you would conduct Weber’s test

A

Place a vibrating tuning fork in the middle of the forehead and ask the patient if the sound is the same in both ears

45
Q

Describe a normal result for Weber’s test

A

Sound is heard equally well on both sides

46
Q

Explain how conduction deafness may present from Weber’s test

A

The sound is usually heard louder in the affected ear due to the fact the vibrations reach cochlea by both air and bone, and in affected ear these two are out of tune so interfere more in the sensitive ear

47
Q

Describe how sensorimotor deafness would present from Weber’s test

A

The sound would be heard more loudly in the unaffected ear

48
Q

Give some examples of middle ear disorders

A

Perforation of tympanic membrane, glue ear (otitis media) or otosclerosis

49
Q

What can middle ear disorders lead to?

A

Conduction deafness

50
Q

What are the two most common tumour types of the internal auditory canal, cerebellopontine angle and skull base?

A

Schwannomas and meningiomas

51
Q

Describe schwannomas

A

Benign neoplasms which arise from the sheaths of cranial nerves

52
Q

Name some of the symptoms of a vestibular schwannoma

A

Unilateral hearing loss, tinnitus and disequilibrium

53
Q

Where do meningiomas most commonly occur?

A

Cerebellopontine angle

54
Q

How do meningiomas develop?

A

They develop from the arachnoid layer of the meninges

55
Q

What are epidermoids?

A

Type of rare intracranial mass where patients become symptomatic in a gradual manner; symptoms are related to mass location in the cranium

56
Q

What is the function of Wernicke’s area?

A

Involved in fluent and meaningless speech and therefore any damage causes severely impaired speech understanding

57
Q

What is the function of Broca’s area?

A

Involved in abbreviated and ungrammatical meaningful speech and therefore damage causes impaired speech understanding where the syntax conveys the meaning

58
Q

What is the arcuate fasciculus?

A

Tissue that connects Broca’s and Wernicke’s areas and therefore damage to this will result in global aphasia

59
Q

What may the result be of damage to the angular gyrus?

A

Can lead to alexia (can’t read) with agraphia (can’t write) but the individual can comprehend speech and talk themselves

60
Q

Which part of the brain is abnormal in dyslexics?

A

Angular gyrus

61
Q

What is the purpose of auditory reflexes?

A

Prevent damage to the eardrum and distinguish sounds from the background

62
Q

Describe what is meant by the ‘attenuation reflex’

A

This is activated by your own voice/loud sounds and causes contraction of muscles in the ear in order to dampen the transmission from middle to inner ear to prevent damage. This reflex is also stimulated by low frequencies so that higher frequencies can be discerned

63
Q

What is a weakness of the attenuation reflex?

A

There is a delay of 50-100ms after the stimulus and therefore doesn’t offer much protection from very sudden loud sounds

64
Q

What happens if there is damage to the attenuation reflex pathway?

A

Hyperacuisis results

65
Q

Which parts of the central nervous system does the blink/startle reflex involve?

A

Facial nerve and reticular formation

66
Q

Describe the function of the blink reflex

A

Works to protect the back of the neck (whole body startle) or the eye (blink), and this is a rapid reflex

67
Q

Where is the auditory cortex located?

A

Temporal lobe in the superior temporal gyrus

68
Q

What are the functions of the auditory cortex?

A

Identify complex auditory sounds, detect changes in auditory environment, learn about behaviour-related sound, integrate attention with auditory processing, and higher functions such as language and musical interpretation

69
Q

Describe the main functions of the auditory system

A

Hearing - distinguishing different sounds and localisation of sounds
Language - production and comprehension of language

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