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Anatomy and Neuroscience > Week 8- Visual, Auditory and Vestibular Sensory Systems > Flashcards

Week 8- Visual, Auditory and Vestibular Sensory Systems Flashcards

1
Q

Describe the “travel” of sound

A

Longitudinal waves that move in a back-forth motion

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2
Q

What is high pressure?

A

Compression

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3
Q

What is low pressure?

A

Rarefaction

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4
Q

What is a period?

A

The time for a particle to move 1 cycle

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5
Q

What does frequency refer to and what is its units?

A

= 1/Period (seconds) and is measured in Hz

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6
Q

What is a wave length?

A

The distance particles travel

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7
Q

What constitutes a louder sound on a graph depicting sound frequency?

A

greater amounts of pressure between peaks

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8
Q

What is the normal human range of hearing?

A

20Hz to 20kHz

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9
Q

What is sound pressure level?

A

Conversion of pascals

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10
Q

What is a decibel equal to?

A

20*log10(X)

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11
Q

What dB range to humans hear over

A

120dB SPL range

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12
Q

Name the basic features of outer ear anatomy

A
  • Pinna (auricle)
  • External auditory meatus
  • temporal bone
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13
Q

Name the basic features of the middle ear

A
  • Tympanic membrane

- Ossicles (malleus, incus and stapes)

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14
Q

Name the basic features of the inner ear

A
  • Cochlea

- Vestibular systems (semicircular canals and otoliths)

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15
Q

What are the components of the pinna?

A 
Helix
Antihelix
Lobule
Concha
Tragus
Antitragus
Intertragical notch
Triangular fossa 
Scapha
Darwins tubercle (not everyone has one)
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16
Q

What is the pinna made up of?

A

Elastic cartilage covered by stratified squamous epithelium

  • hair follicles
  • sebaceous glands
  • ceruminous glands (modified sweat glands)
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17
Q

How does the outer ear contribute to the generation of ear wax?

A

Via the ceruminous glands

Modified sweat glands

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18
Q

What is the function of the pinna?

A
  • Funnels sound into the ear canal
  • 2-fold increase (6dB) increase in pressure at typmanum
  • PInna fold alter the characteristics of sound
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19
Q

What are pinna cues?

A

When the pinna folds deflect the sound to change the spectrum slightly

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20
Q

What are the spectral features of sound?

A

Interaural timing difference (ITD)

Interaural level difference (ILD)

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21
Q

Describe the physical features of the middle ear

A
  • Temporal bone (aerated, mastoid)
  • tympanic membrane (eardrum)
  • ossicles (malleus, incus and stapes)
  • Eustachian tube
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22
Q

describe the nerve distribution across the tympanic membrane

A

Does not have many nerve endings, most sensitive around the outer edges (very painful)

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23
Q

What is the name of the head of the malleus?

A

Umbo

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24
Q

How does the ear equalise air pressure?

A

Pulls open the eustatian tube when the levator and tensor palati pull the soft palate up during swallowing

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25
Q

What can occur in the petrous bone cavities of the middle ear?

A

Mucous filling cavity, causing the formation of infection

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26
Q

What are the functions of the middle ear?

A
  • Ossicles transmit vibrations to inner ear
  • Tympanum: stapes foot plate provides 3-fold gain (10dB)
  • @ low-frequencies, middle-ear pressure acts on both windows, limiting gain
  • Tensor tympani and stapedius muscles suppress middle ear gain

Total = 26dB gain

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27
Q

Describe the features of the inner ear

A

Cochlea

  • Oval window (stapes footplate)
  • round window (clear membrane)
  • Bony Labyrinth (perilymph)
  • Membranous labyrinth (endolymph)

Vestibular System

  • Otoliths (Saccule and utricle)
  • Semicircular canals (lateral, posterior, anterior)
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28
Q

Why is the cochlear in a spiral shape?

A

A long membrane needing to fit in a small space. Became spiralled throughout evolution and development

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29
Q

What fluid is found within the scala vestibuli and scala tympani?

A

Perilymph (high [Na+])

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30
Q

What components make up the bony labyrinth?

A

Scala vestibuli and scala tympani

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31
Q

What fluid is associated with the scala media?

A

Endolymph (high [K+])

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32
Q

What is the name given to the very apex of the cochlea, where the scala vestibuli and scala tympani join?

A

Helicotrema

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33
Q

Where does the organ of corti sit?

A

Basilar membrane

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34
Q

Describe the basilar membrane

A

trampoline like structure. transfers fluid pressure changes (waves) between SV and ST. Organ of Corti moves with the membrane

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35
Q

Describe Cochlear Tonotopy

A
  • Stapes vibrations cause increased pressure in SV than ST, displacing the organ of Corti
  • Fluid pressure wave generates OoC wave that travels along the partition towards the apex
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36
Q

What is the Travelling wave?

A

organ of corti wave generated by fluid pressure wave that travels towards the apex of the cochlear

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37
Q

Describe the mechanical properties of the basilar membrane

A

Varies along its length

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38
Q

Describe the difference between the base and apex of the cochlear

A

Base- narrow & stiff, has high-frequency resonance

Apex- broad and floppy, has a low-frequency resonance

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39
Q

How many rows of outer hair cells are there and what are their role?

A

3 rows of outer hair cells

Acts as the cochlear amplifier

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40
Q

How many rows of inner hair cells are there and what are their role?

A

1 row of inner hair cells

Transduction to action potentials- transmit the sensation of sound

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41
Q

What sits on the basilar membrane of the organ of Corti

A

supporting cells

42
Q

Where is the techtorial membrane?

A

overhangs over the organ of Corti

43
Q

Where is the Stria Vascularis and what does it do in the organ of Corti?

A

Located on the lateral wall

Actively pumps K+ into endolymph

has the highest metabolic rate of any tissue in the human body

44
Q

Where are nerves located in the cochlea?

A

the cochlear nerve and the spiral ganglion are located in the Modiolus

45
Q

Where do neurons synapse in the cochlea?

A

Neurons synapse with the basal surface of hair cells

46
Q

What is a MET channel?

A

Mechano-Electrical Transduction Channel

47
Q

What is found on the tops of the hair cells and how are they linked?

A

Stereocillia is found on top of hair cells. Tip links connect the two neighbouring cilia of each hair cell, from the tallest to the K+ channel on the shortest.

48
Q

How do K+ channels open?

A

With the movement of the basilar membrane, causing the taller stereocilia to bend and mechanically pull open the channel. Being surrounded by endolymph means that K+ is readily moved into the hair cell, depolarising them.

49
Q

What happens when OHCs depolarise?

A

OHCs contract when they depolarise. This leads to the pumping of the vibration, triggering the release of glutamate from IHCs onto the afferent neuron

50
Q

Where does active amplification increase the vibration of the travelling wave?

A

At the tip of the travelling wave

51
Q

Describe non-linear amplification

A

OHC amplification doesnt work well for loud sound

  • Increases frequency sensitivity
  • Increases dynamic range
52
Q

What does loss of OHC gain result in?

A

Poor hearing and poor discrimination

53
Q

Describe endocochelar potential (EP)

A
  • Stria Vascularis pumps K+ into 150mM K+ fluid @90mV

- MET channels open, K+ flows into hair cells, down EC gradient

54
Q

Describe the effect on hearing if stria is dysfunctional

A

The OHC gain doesn’t work, resulting in a 40dB hearing loss

  • Most common form of hearing loss
  • High frequency hearing loss
  • Blood supply begins to drop off with age, resulting in less vibrations
55
Q

Describe the segmentation of auditory processing

A

Cochlea

Cochlear Nucleus (brainstem; midbrain) 
- spectral and temporal coding

Superior Olivary Complex (MSO, LSO)
- ILF and ITD coding

Inferior Colliculus (midbrain) 
- Integration with other senses

Medial Geniculate Nucleus (thalamus)
- Attentional Filter

Auditory Cortex
- Perception and recognition

56
Q

What are the basic functions of the vestibular system?

A

Integrating data storage system

  • Eye
  • Cortex cerebellum
  • cortical awareness of body/head/motion
  • eye movement
  • control of posture
  • control of motor skills
  • joint position
57
Q

List the components of motion measurement

A 
Position 
Velocity 
Acceleration 
Jerk (vestibular neurons fire off at jerk) 
Rotation and translation 
gravity
58
Q

What are the 3 directions of the semicircular canals?

A

Superior
Posterior
Horizontal

Left and right of each, resulting in 6 total

59
Q

What is the ampulla of the semicircular canals?

A

The enlarged part of the semi.circ.canals

60
Q

What are the cristae of the vestibular system?

A

Sensory epithelium- hair cells

61
Q

What is the cupula?

A

gelatinous cap that overlies hair cells in the vestibular system

62
Q

What is the vestibule?

A

perilymph space

63
Q

What are the otoliths?

A

Saccule (saccular macula) –> cochlea

Utricle (utricular macula) –> semi. c.

64
Q

What layer lays over the neuroepithelium?

A

Otoconial layer

  • Crystals that are denser than water
  • tugs on gelatinous mass when head is tilted
65
Q

Describe the anatomy and function of the otoliths

A
  • Hair bundles move with body
  • otoconial layer lags behind
  • Hair bundles (tip links and MET) face in a particular direction
  • Responds to translation n all directions
  • MET open= depolarisation= glutamate release
  • No active amplification
66
Q

Describe the difference in positions of the utricular and saccular maculas

A

Utricular: vertical
Saccular: horizontal

Both sensitive to movements in most linear directions (not so sensitive to rotations)

67
Q

Describe the anatomy and function of the semicircular canals

A
  • Left-right posterior and anterior canals align so that geometry allows for sensitivity in all head planes
  • Hair cells rotate with head
  • Endolymph lags, moving Cupula due to inertia
68
Q

Describe the function of the vestibular ocular reflex

A

VOR keeps eyes focused forward during head rotation

when the head turns left, canal fluid doesnt as much

eyes rotate right due to excitation and inhibition

69
Q

Describe the differences between the posterior and anterior cavities of the eye

A

PC: filled with vitreous humour (gel)

AC: filled with aqueous humour, produced by ciliary epithelium and reabsorbed by sclera venous sinus

70
Q

Why is light required to be refracted in the eye?

A

Light entering the pupil is refracted to focus the image on the retina

71
Q

How is refraction achieved (%)

A

Achieved by the cornea (75% and the lens (25%)

72
Q

What does the amount of refraction in the eye depend on?

A

The amount of refraction that occurs depends on the distance of the object

73
Q

Describe the process of accommodation in the refraction of light

A
  • Ciliary muscles (oculomotor nerve)
  • Ciliary processes
  • Suspensory ligaments
  • Lens stretched
74
Q

What does the retina consist of?

A
  • pigmented layer of melanin containing cells
  • neural layer containing neurons
  • retinal blood vessels
  • optic nerve
75
Q

What are the sublayers of the neural layer of the retina? (from where light is received first)

A

Ganglion cell layer

bipolar cell layer

photoreceptor layer (cones and rods)

76
Q

What are photoreceptors?

A
  • located in the deepest layer of the retina
  • transduce light energy into a receptor potential
  • contain photopigments that absorb light
77
Q

Describe the workings of rods as photoreceptors

A
  • Respond to low levels of light
  • Decreased visual acuity
  • sensitive to light but not so much features of light
  • contain rhodopsin, forming when light levels decrease (slow process, hence why it takes a while to see clearly in the dark)
78
Q

Describe the workings of cones as photoreceptors

A
  • respond to high levels of light
  • increased visual acuity
  • 3 different cone types
  • Blue, red and green absorbing the same colour of light
  • we have colour vision due to different wavelengths of light activating different photopigments of different cone types
79
Q

What is the central fovea?

A

only cones present allowing increased visual acuity

80
Q

What is the optic disc?

A

Also known as the blind spot, does not have rods, nor cones present. Arteries and veins emerge from here

81
Q

Describe the basics of how visual pathways work

A
  • lens produces an inverted laterally reversed image (upside down, back to front)
  • each eye has a right and left visual field
  • Temporal side and nasal side
82
Q

What is meant by the binocular field?

A

overlap occurs between what the left and right eyes see in their visual fields, forming the central binocular field.

83
Q

Which visual field corresponds to what side of the brain?

A

LVF: right brain
RVF: left brain

84
Q

Describe the end location of the visual pathway

A

Visual pathway ends in he visual cortex above and below calcarine sulci

  • Lower VF= above
  • Upper VF= below
  • Central VF= posterior
  • Peripheral VF= anterior
85
Q

What is the effect of a lesion on the visual pathway?

A

Lesions in particular parts of the brain cause predictive visual field losses

86
Q

What are the classifications of vision loss?

A

Hemianopia: loss of half a visual field

Bilateral: both eyes

Quadrantanopia: loss of 1/4 visual field

Homonymous: same visual field in both eyes

87
Q

SLIDE 60

A

STREAMS OF VISUAL PROCESSING

88
Q

What nucleus receives retinal and visual cortex inputs?

A

Edinger-Westphal nucleus

89
Q

If light was shone in the left eye, what response would be expected?

A
  • Contraction of left pupil (direct response)

- Contraction of right pupil (consensual response)

90
Q

What occurs in the eyes when an object is closer

A

Edinger-Westphal adjusts ciliary muscle and medial rectus muscle to focus on the closer object

91
Q

What fluid is contained in the anterior and posterior cavities of the eye?

A

Anterior: aqueous humour
Posterior: vitreous humour (gel)

92
Q

Under what circumstances do the ciliary muscles contract?

A

High frequencies/amounts of light

93
Q

What cranial nerve innervates the ciliary muscle?

A

Oculomotor nerve

94
Q

Where is the optic chiasm located in relation to the hypothalamus?

A

Located in the forebrain, directly in front of the hypothalamus

95
Q

Which parts of the visual fields are directed to the visual cortex above and below the calcarine sulcus in the occipital lobe?

A

Lower visual fields = above

upper visual fields= below

96
Q

What is the difference in the ear lobe compared to the rest of the pinna? (think piercing)

A

Does not contain cartilage

97
Q

What is the different innervations of the auricle?

A 
Anterior= trigeminal (V) 
Posterior= Facial (VII)
98
Q

What do the ceruminous glands of the subcutaneous tissue secrete?

A

Cerumen (ear wax)

99
Q

What innervates the EAM?

A

Vagus (X)

100
Q

State the order of the ossicles including their attachments (if applicable)

A

Malleus (tympanum), incus, stapes (oval window)

101
Q

Name the location of receptors, gelatinous material and stimulus of the semicircular canals

A

Crista, cupula, rotation of the head

102
Q

Name the location of receptors, gelatinous material and stimulus of the utricle/saccule

A

Macular, otalithic membrane and acceleration

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