Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MD4001 > Hearing, Taste and Smell > Flashcards

Hearing, Taste and Smell Flashcards

1
Q

Explain the physics behind the pitch, and intensity of sound.

A

Frequency/wavelength is responsible for the pitch (higher frequency = higher pitch)

Amplitude is responsible for the intensity/loudness of sound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the whole process of transduction of sound through the ear.

A

1) First transduction: sound waves strike the tympanic membrane and become vibrations
2) Sound wave energy is transferred to the three bones of the middle ear, which vibrate
3) Second transduction: stapes is attached to the membrane of the oval window. Vibrations of the oval window create fluid waves within the cochlea.
4) Third transduction: fluid waves push on the flexible membranes of the cochlear duct. Hair cells bend and release NT.
5) Fourth transduction: NT release onto sensory neurones create APs that travel through the cochlear nerve to the brain
6) Energy from the waves transfer across the cochlear duct into the tympanic duct and is dissipated back into the middle ear at the round window.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Identify the main structural components of the outer (external) ear.

A

– Pinna (auricle)
• Tragus

– External auditory [acoustic] meatus
• Cartilaginous and bone parts; not in the same direction
• Ceruminous glands
• At end of EAM, tympanic membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Identify a clinical use of the tragus.

A

If suspecting external acoustic meatus inflammation, tap on tragus. If it causes pain, likely arising from external acoustic meatus. Otherwise may arise from TMJ, whose pain is similar to external acoustic meatus pain.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the function of ceruminous glands in the outer ear ?

A

Secrete wax-like secretion called cerum, whose function is to make eardrum soft and waterproof, and
prevents maceration of EAM when submerged in water.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

State the nerve supply of the external ear.

A

• Supplied by auricular branch of Vagus and auriculotemporal branch of trigeminal nerve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Explain which nerve may be irritated when using cotton buds, and the effect of this.

A

Using cotton bud may lead to cough reflex due to irritation of vagus nerve.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the shape of the tympanic membrane ?

A

Concave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What should you look for in examination of the tympanic membrane ?

A 
Color
Shadow of handle of malleus (and possibly shadow of Chorda Tympani)
Curvature
Any lesions
Transparency
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Identify the main divisions of the tympanic membrane, as well as the significance of the main ones.

A

4 quadrants:

  • Safest quadrant is antero-inferior quadrant (for insertion of tube into eardrum for drainage of pus from middle ear cavity in middle ear infections)
  • Chorda tympani is in the postero-superior quadrant
  • Triangular reflection of light (AKA Politzer’s triangle) (from otoscope) in the antero-inferior quadrant
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Identify the main structures present in the middle ear.

A

Middle ear is an air filled cavity with ossicles, muscles and nerves.

OSSICLES
-Malleus, incus, stapes, all attached to the walls by ligaments

SMALL MUSCLES

  • Tensor tympani
  • Stapedius

NERVES
-Chorda tympani

OTHER
-Mucous membrane (continuous with pharynx)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How are the ear and pharynx connected ?

A

From middle ear to nasopharynx via Auditory / pharyngotympanic / Eustachian tube.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe innervation of the middle ear.

A

The middle ear is supplied by the auriculotemporal (fifth cranial) and tympanic (ninth cranial) nerves (CN9 innervates mucuous membrane of middle ear) and by the auricular branch of the vagus..

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the function of the ossicles in the middle ear ?

A

Transmit the vibration from the tympanic membrane to the inner ear

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Identify possible routes of infection from the middle ear.

A

Middle ear infection can spread, and may result in:

  • Mastoid sinus infection (because middle ear cavity continuous with mastoid air cells)
  • Brain, meningo-encephalitis (roof of middle ear cavity is very thin layer of bone; infection of middle ear can cause erosion of bone and spread)
  • Internal jugular vein hemorrhage (infection can erode floor of middle ear cavity, and cause hemorrhage)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe the arrangement of the middle ear ossicles, relating this to their function.

A

Handle of malleus is attached to tympanic membrane (so when latter vibrates, causes vibration of movement along ossicles, so vibration is then transmitted to base of stapes, which is adjacent to the oval window of the inner ear)

Because of the difference in area between tympanic membrane, and stapes and lever, sound waves are amplified by 15 when they get to the oval window.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Why does the body need to amplify sound waves ?

A

Because after the oval window, need to create waves on a fluid, so more force is require to create waves, so must be amplified.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the function of the tensor tympani ? What is its innervation ?

A

Tensor tympani (attached to handle of malleus) pulls tympanic membrane medially –> increase the tension in response to loud noises –> reduce the vibration of the tympanic membrane

Innervation: mandibular nerve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the function of the stapedius ? What is its innervation ?

A

Stapedius m. pulls base of the stapes away from oval window (so not all vibrations are transferred to middle ear) (protects inner ear from injury from loud noise)

Innervation: facial nerve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Identify a possible pathology of the muscles of the middle ear.

A

If they don’t function adequately, result in Hyperacusis (constant tinnitus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe the response in the ear when a very large sound is emitted.

A

Very large sound, body tries to protect inner ear:

Sound waves hit tympanic membrane, transfers back to cochlear nerve, to cochlear nuclei, to superior olivary
nucleus (which is connected to motor nucleus of facial nerve and motor nucleus of TriG), so
tensor tympani and stapedius
contract, rendering tympanic membrane tenser, which will not allow all the sound waves to be transferred, and the stapes will prevents all waves going into inner ear.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the smallest muscle of the human body ?

A

Stapedius

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe structure of the pharyngotympanic tube.

A
  • Walls are normally collapsed (to restore P within middle ear cavity, need to open these walls)
  • Tube is short and straight in children (hence upper resp infections in children can easily disseminate to middle ear cavity)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How is the pharyngotympanic tube opened ?

A

Actively opened by the simultaneous contraction of the tensor veli palatini and salpingopharyngeus muscles (e.g. in swallowing)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Identify the main components of the inner ear.

A 
BONY LABYRINTH
• Vestibule
-Utricle (inside vestibule)
-Saccule (inside vestibule) 
• Semi-circular canals (bony)
-Ducts (membranous, inside circular canals)
• Cochlea

MEMBRANEOUS LABYRINTH (inside bony labyrinth)

PERILYMPH (between bony and membranous labyrinths)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Are vestibule, semi-circular canals, and cochlea involved in hearing or balance ?

A

Cochlea- Hearing

Semi-circular canals and vestibule- Balance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the function of the perilymph in hearing ?

A

When the base of the stapes causes sound wave, wave goes through perilymph.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Describe the structure of the cochlea.

A

The cochlea houses the cochlea duct of the membranous labyrinth – the auditory part of the inner ear. It twists upon itself around a central portion of bone called the modiolus, producing a cone shape.

The presence of the cochlear duct creates two connected perilymph-filled chambers above and below:

  • Scala vestibuli: Located superiorly to the cochlear duct. Continuous with the vestibule. At its end, get oval window which is covered by base of stapes. Vestibular membrane separates SV from CD.
  • Scala tympani: Located inferiorly to the cochlear duct. It terminates at the round window, which is covered by membrane. Basilar membrane and osseous spiral lamina separates ST from CD.

Connected via helicotrema at the tip of the cochlea.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Describe changes in the cochlea when a sound is received.

A

When base of stapes creates sound wave on fluid, wave passes through scala vestibuli, to helicotrema, to
Scala Tympani. Because fluids cannot be compressed, when base of stapes causes this sound wave, it has to be counter balanced, so membrane covering round window bulges in and out to compensate for P changes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is the significance of the basilar membrane ?

A

This is where organ of Corti (hearing receptors) is located.
Tectorial membrane projects over the receptors and is involved in hearing (when basilar membrane vibrates, receptors vibrate with it, and they will hit tectorial membrane)

31
Q

Describe the process of frequency detection.

A
  • Structure of basilar membrane changes from short and stiff, to long and floppy along the length of the cochlea.
  • Resonant frequencies vary along the cochlea with high frequency at the base and low at the apex(/helicotrema).
  • When the basilar membrane vibrates at the resonant frequency, it absorbs all the kinetic energy of the wave and effectively stops it at that point.
32
Q

Describe the process of signal detection.

A

Signal detection occurs at the organ of Corti

  • Upward deflection of the basilar membrane moves the inner and outer hairs (embedded in fluid just inferior to tectorial membrane) laterally with respect to the tectorial membrane.
  • 95% of the cochlear nerve ending terminate on the inner hair cells
  • Outer hair cells increase the sensitivity of inner hair cells (to suppress background noise and concentrate on specific frequency) (through superior olivary nucleus)
    • This can tune the cochlea by
    amplifying select frequencies
33
Q

What are the main roles of the superior olivary nucleus in the process of hearing ?

A
  • Prevents damage from sound
  • Increases sensitivity of inner hair cells using outer hair cells (so can suppress background noise and hear specific frequencies)
34
Q

Describe the location of the hair cells.

A

Hair cells are embedded in fluid just inferior to tectorial membrane. When basilar membrane starts to vibrate, hair cells will move in one direction, laterally.

35
Q

Describe the process of signal transduction in the cochlea.

A

Displacement of stereocillia in one direction opens K channels, K+ influx into neurons, depolarisation, perceive this as sound.

When back to original position, links close, no K+ influx, no sound

36
Q

Describe the process of cochlea tuning.

A
  • Inner hair cells become depolarised and send signals to the cochlear nerve thence to the CNS
  • Mechanical displacement does NOT provide the shaprness of pitch discrimination recorded (so must be a system to enhance this)
  • Outer hair cells stimulated by the basilar membrane to depolarise, but this causes (as well as action potentials) the cell to contract
  • Precise mechanism of the effect is still being researched but the effect is to enhance the auditory signal at the center of the standing wave and inhibit on either side
  • Tuning is also under active Olivocochlea neuronal control: Cochlear nerve connected to cochlear nucleus, which is connected to SON, which regulates this and feeds into outer hair cells which increase sensitivity of inner hair cells . End result is release of Ach onto the inner hair cells causing them to depolarise. This effectively damps down hearing in areas of pitch which are of no interest to the listener (background noise etc)
  • Outer hair cells act as an amplifier for the vibrations at the organ of corti
  • Knockout of Prestin – (the cell membrane outer hair cell motility protein) and you loose 40-69 decibels of your hearing at that frequency i.e. the outer hair cell amplifier provides a 40-60 decibel gain in sensitivity.
37
Q

Identify ototoxic drugs, and their specific effects on hearing.

A

Kanamycin (aminoglycoside) preferentially kills outer hair cells in a specific point along the cochlea results in a specific frequency hearing loss at that point.

Gentamycin

Aspirin (toxic to cochlear nerve)

38
Q

Define otoacoustic emission (sound comes out of ears). What proportion of these are spontaneous ?

A

Sound coming out of inner ear (from flow of perilymph), sometimes heard by patients and perceived as tinnitus

50% spontaneous, remainder can be evoked (good tests in babies/infants for function up to the inner hair cells)

39
Q

Describe the path of electrical signals producing sound (i.e. auditory pathways).

A
  • Hair cells of the organ of Corti generate an electrical signal
  • Peripheral extensions of the bipolar neurons at Spiral ganglion synapse with hair cells of the Organ of Corti
  • Central extensions of bipolar neurons form the cochlear nerve (1st order)
  • Cochlear nerve synapses at anterior and posterior cochlear nuclei
  • Central extensions of 2nd order neurons splits up, with some travelling ipsilaterally, but most contralaterally (i.e. decussate) up to the respective superior olivary nucleus
  • Lateral lemniscus (3rd order) ascend and synapse at inferior colliculus
  • 4th order neurons project to the medial geniculate nucleus of the thalamus where they synapse
  • 5th order neurons join the auditory radiation to the auditory cortex (temporal lobe)

Secondary projections from the primary, and some from the thalamic association areas then go to auditory association cortex

40
Q

Which structure is also known as hearing reflex center ?

A

Inferior colliculus

41
Q

Identify any collaterals to the main auditory pathway.

A

Collaterals from the pathway project into the reticular formation and the vermis of the cerebellum causing arousal responses to noise (e.g. sleeping or relaxing and hear very loud noise, all neurons in body awake)

42
Q

To what extent is sound topographically represented in the brain ?

A

Sound is relayed tonographically to these cortical areas, with lower frequencies to the anterior in most maps though there are variations

43
Q

How do we determine direction of sound ?

A
  1. Volume (as move away from source, pitch decreases)
  2. Sound shadow, sound from one side hits the head, which then generates a sound shadow on the other side in which the volume is less. Comparison of signal intensities from both ears determines the ear closest to the sound
  3. Sound lag, sound from a particular direction enters one ear before the other and so there is a slight delay between the sound arriving ipsilaterally at the auditory cortex, and that arriving contralaterally. Enhanced version of this used by owls for prey location.
44
Q

Which type of sound is sound lag most effective for ? Sound shadow ?

A

Sound lag works at lower frequencies, better at determining horizontal direction than sound shadow (which is good for high frequencies)

45
Q

Which of volume, sound shadow, or sound lag (or other) best detects front to back or above to below directionality ?

A
  • Neither method detects front to back or above to below directionality
  • This is achieved by the folds in the pinna which changes the characteristics of sound coming from above compared to below etc
46
Q

Identify the main kinds of deafness, as well as possible causes of each.

A

CONDUCTION DEAFNESS
− A blockage in the outer ear
− Infection in either the outer or inner ear
− Ossification of the small bones in the middle ear
− Rupture of the tympanic membrane

SENSORY-NEURAL DEAFNESS
− Breakdown of the cochlea and associated mechanisms,
− Damage to the auditory nerve
− Damage to the auditory cortex

47
Q

If two people three feet apart have to shout in order to hear each other, what is the minimum background noise level ?

A

Higher than 85 decibels

48
Q

At what noise level is the allowable exposure time 0 minutes ?

A

115 decibels

49
Q

What are some symptoms of hair cell damage ?

A
  • Tinnitus

- Hearing Loss

50
Q

How many decibels constitutes normal hearing ?

A

Being able to hear 20 decibels means normal hearing

51
Q

Graph hearing loss associated with loud noise exposure.

A

Refer to slide 30

52
Q

Identify the main hearing tests in use today.

A

Rinnes test

Webber’s test

53
Q

How are Rinne and Webber’s tests performed ?

A

Weber’s test – tuning fork in the middle of the forehead, heard equally on both sides (if normal). If sensorineural hearing loss then sound perceived as coming from normal ear, and if conductive hearing loss then sound perceived as coming from affected ear

Rinne’s test – air conduction is better than bone conduction (AC>BC): positive test

Use 512 Hz tuning fork for both.

First perform Weber’s, then if don’t hear it in the midline then do Rinne’s to determine whether sensorineural (AC>BC) or conductive (BC>AC on affected side).

54
Q

Describe the result of the following on hearing:

  • Loss of association cortex
  • Loss of both primary cortex areas
  • Loss of one side
A
  • Loss of association cortex leads to loss of meaning of sounds such as those seen in Wernicke’s lesions, but not to loss of differentiation of tone or frequency
  • Loss of both primary cortex areas dramatically reduces sensitivity to sound
  • Loss of one side has much less effects as the auditory pathway runs
    bilaterally from the cochlea nucleus
55
Q

What’s a normal result for Rinne test ?

A

Air conduction > Bone conduction

56
Q

How does taste happen, molecularly ?

A

Interaction of dissolved molecules with taste buds (saliva essential for this to occur)

57
Q

Identify the main primary tastes.

A

Five/Six primary tastes are recognized
− Sweet: Sugar, glycols, ketones
− Sour: H+ ions
− Salty: NaCl
− Bitter: Quinine, alkaloids found in toxic plants (taste threshold
0.000008M, because bitter substances typically toxic)
− Umami: Triggered by glutamate. Truffles, meat, aged cheese, and
tomatoes
− Oleogustus: Taste of the fatty acid (unpleasant)

58
Q

To what extent is taste related to smell ?

A

Closely related, when nose is blocked, cannot get as much taste

59
Q

What’s a papilla ? Identify the main papillae, along with the main features of each.

A

Papillae house taste buds on the tongue

ANTERIOR 2/3
Foliate papilla
• Poorly developed

Fungiform papilla
• Most numerous
• Supplied by facial nerve

Vallate papilla
• Along sulcus terminalis
• Suppled by Glossopharyngeal
• More sensitive to bitter

Filiform (not associated with taste buds)

60
Q

Where in the body are taste buds located ?

A

Taste buds are located on the tongue, on the oral surface of the soft palate, the posterior wall of the oropharynx,and the epiglottis as well

61
Q

Describe taste innervation of the tongue, oropharynx, epiglottis, soft palate.

A

Taste from the anterior 2/3 of the tongue is detected by peripheral extensions of sensory neurons in geniculate ganglion of facial nerve (nerve is chorda tympani, which travels with lingual nerve, goes through infratemporal fossa, petryotympanic fissure, middle ear cavity, then joints facial nerve)

Taste from the posterior 1/3 -including vallate papillae- of the tongue and oropharynx is detected by peripheral extensions of sensory neurons in inferior ganglion of glossopharyngeal nerve

Taste from epiglottis and soft palate are by vagus.

62
Q

Describe nervous taste pathways, starting from taste buds.

A

• Central processes of neurons conveying taste (facial, glossopharyngeal and vagus) form tractus solitarius

• Tractus solitarius synapse in
nucleus of tractus solitarius (gustatory nucleus)

  • Axons of 2nd order neurons cross the midline
  • Join medial lemniscus (NOT ONLY about JPS)
  • 2nd neurons synapse in thalamus
  • 3rd neurons project to the somatosensory cortex
  • Gustation has a limbic component via the thalamus, and can activate brainstem nuclei for salivation, or vomiting (when taste something, may drool (if like it), or may cause vomiting)
63
Q

Is olfaction highly developed in humans, cf other species ?

A

No

64
Q

Identify the main categories of smells. How rapidly does accommodation occur ?

A 
Odors are grouped into following cateogories
(not primary odors but formed of a spectrum of odors in specific proportions): 
1) Camphoraceous
2) Musky
3) Floral
4) Pepperminty
5) Ethereal
6) Pungent
7) Putrid

Accommodation occurs relatively rapidly.

65
Q

What are the main components of the olfactory system ?

A

Composed of:

  • Olfactory epithelium in the olfactory region
  • Receptor cells (bipolar neurons)
  • Axons that project through the base of the skull to the olfactory bulb
  • Neuronal tract to multiple olfactory destinations in the brain

ALSO
- Glandular Goblet cells (Bowman glands) moistens the olfactory cells (facilitates olfaction) and secrete mucus which dissolves odorants

66
Q

What is the life span of olfactory neuroepithelial cells ? How are dead neuroepithelial cells replaced ?

A

40-60 days

REGENERATE! from basal cells (basal cells can be used as
stem cell)

67
Q

What proportion of inhaled air comes in contact with olfactory receptors ? How can we increase this ?

A

Only about 2% of inhaled air comes in contact with the olfactory receptors
− Sensitivity can be increased
by forceful sniffing

68
Q

Describe nervous olfactory pathways, starting from the breakdown of odorants.

A

• Odorants are dissolved in mucus secreted by Bowman glands
• Cilia of receptor cells (bipolar neurons) are activated
• The central processes of receptor cells form olfactory nerve that pass through the cribriform plate to synapse in the olfactory bulb
• Olfactory bulb
• Olfactory tract
− Medial olfactory stria –> limbic system
− Lateral olfactory stria –> olfactory cortex in medial temporal lobe

PATHWAY ENTIRELY IPSILATERAL

69
Q

Explain why smelling pepper can cause sneezing.

A

Certain chemicals can activate other cranial nerves as well as the olfactory nerves and cause reactions. Pepper does just this.

70
Q

Describe the structure of olfactory nerve.

A

Olfactory nerve is covered

with connective tissue of meninges

71
Q

State a unique feature of the nervous pathways for olfaction as opposed to the other senses.

A

Sense goes to cortex before thalamus (whereas all other senses start with thalamus first THEN cortex)

72
Q

Identify the main causes of anosmia.

A
  • Idiopathic anosmia (25%)
  • Nasal / sinus disease (25%)
    •Colds
    •Polyps
    •Other blockages
  • Head Trauma (15%) (can lead to permanent anosmia)
    •Leading to damage to frontal lobe processing
    •Leading to damage to ascending nerves at cribriform plate
    •Permanent compression of the nasal passages
  • Alzheimer’s preceding (2-5%)
  • Congenital anosmia (1%)
73
Q

Define parosmia, and state a possible cause.

A

Distorted often unpleasant sense of smell caused by damage to the lining at the top of the nose (e.g. upper respiratory viral infections)

MD4001 (74 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions