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Medicine phase 1 > week 12 - special senses > Flashcards

week 12 - special senses Flashcards

1
Q

structural components of the eye

A 
sclera
pupil
iris 
cornea
optic nerve
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2
Q

structure of sclera

A

White of the eye, fibrous and elastic tissue, outer layer of eye - allows for the contrast of the eye to determine where a person/animal is looking

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3
Q

structure of the pupil

A

middle of the iris
wider in dark
smaller in light

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4
Q

structure of iris

A

smooth muscle structure which controls the diameter of the pupil via two muscles - sphincter pupillae and dilator pupillae

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5
Q

structure of cornea

A

avascular

common for use in transplant as it cannot reject the tissue due to blood supply as it does not have one

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6
Q

optic nerve structure

A

appears as a solid white structure roughly in the middle of the retina
surrounded by the meningeal layers of the brain, any pressure increases intracranially (eg bleed, tumour or other space occupying lesion) will be transmitted along the nerve and causes bulging of the optic disc - This is called papilloedema and requires investigation as to the cause

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7
Q

what is keratoconus

A

thinning of the cornea resulting in a coning shape and can cause blurring and double vision of the eyes
Surgery may have to be done in more severe cases of a corneal transplant

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8
Q

what is aqueous humour

A

produced in anterior and posterior chambers of the eye from the ciliary bodies
maintains the pressure inside the eye, provides nutrients to eye and protects the eye

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9
Q

what is vitreous humour

A

a gel which occupies the space between the lens anteriorly and the retina posteriorly
mainly contains phagocytes to remove cell debris and is mainly water with no blood vessels

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10
Q

describe the retina

A

the light sensitive layer of tissue of the eye and where the rods and cones are for black and white and colour vision respectively

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11
Q

pathway of nerve fibres in eye

A
  • Visual input comes through pupil -> vitreous humour -> retina -> optic nerves -> optic tract -> optic chiasm -> optic tract -> optic radiation -> occipital lobe
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12
Q

where are tears proudced

A

lacrimal gland

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13
Q

function of tears

A

lubricates movement

removes debris - debris moves from lateral to medial direction into nose

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14
Q

why does your nose run when you cry

A

nasolacrimal duct (in nasolacrimal canal) takes tears from lacrimal gland to nasal cavity

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15
Q

7 bones of the orbit

A 
frontal 
sphenoid
zygomatic
palatine
ethmoid
lacrimal
maxilla
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16
Q

where are the paranasal sinuses

A

maxillary - under eyes
frontal - forehead
ethmoid - posterior to nose
sphenoid - posterior to nose

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17
Q

function of paranasal sinuses

A

reduces weight of skull
allows circulation of mucous
contributes to resonance of sounds

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18
Q

which cranial nerves control eye movement

A

III
IV
VI

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19
Q

7 extraocular muscles and their movements

A

levator palpebrae superioris - keeping upper eyelid open
Superior rectus – elevation of eyeball (also adduction of eyeball and medial rotation)
Inferior rectus – depression of eyeball (adduction and lateral rotation)
Medial rectus – Adducts the eyeball
Lateral rectus – Abducts the eyeball
Superior oblique – depression of eyeball, abduction and medial rotation
Inferior oblique – Elevation, abduction and lateral rotation of the eyeball

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20
Q

which eye nerves supply which muscles

A

Trochlear nerve only supplies superior oblique
Oculomotor nerve – inferior oblique, superior rectus, medial rectus, inferior rectus
Abducent nerve – lateral rectus

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21
Q

how structure of nose relates to its function

A 
incoming air is warmed, humidified, filtered
nose does this best due to:
rich, superficial blood supply,
mucous provides moisture
mucous and hairs trap particles
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22
Q

describe the location of the cribriform plate

A

The olfactory bulb, part of the brain, lies on the superior surface of the cribriform plate, above the nasal cavity
Branches of the olfactory nerve run through the cribriform plate to provide special sensory innervation to the nose

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23
Q

conchae in the nasal cavity

A

increase surface area

increase chance of olfactory exposure

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24
Q

innervation to tongue

A

CN IX - taste and sensation from posterior 1/3
CN XII - motor control of most tongue muscles
lingual nerve - carries axons from CN V and VII for taste and sensation in anterior 2/3

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25
Q

describe the surfaces in the mouth

A

buccal surface - side of the mouth where the surface is towards the cheeks as a surface of the teeth
lingual surface - faces the tongue as a surface of tongue
floor of mouth - mylohyoid muscle and overlying stratified squamous epithelium

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26
Q

epiglottis

A

elastic cartilage which helps close over the trachea during swallowing

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27
Q

describe the ossicles in ear

A

malleus - attached to tympanic membrane
incus
stapes
they transmit vibrations through middle ear

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28
Q

what is the oval/vestibular window

A

opening into the vestibule of inner ear

closed by base of stapes

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29
Q

what is the cochlear/round window

A

opening into the cochlear portion of inner ear

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30
Q

tympanic cavity contains…

A

tympanic membrane
vestibular/oval window
cochlear/round window

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31
Q

what is the helicotrema

A

the location where the tympanic duct and the vestibular duct merge, at the apex of the cochlea

32
Q

what is Reissner’s membrane

A

separates the vestibular duct (scala vestibuli) from the cochlear duct (scala media)

33
Q

function of cochlea

A

sound amplification
conversion from vibration to electrical signal
signal transmitted via cochlear part of CN VII

34
Q

function of semicircular canals

A

balance

vestibular part of CN VIII

35
Q

CN in nose

A

CN I

36
Q

CN in ears

A

CN VIII

37
Q

CN in eyes

A

CN II for vision

CN III IV VI for eye movements

38
Q

what is sound

A

changes in pressure over time - spreads out as a wave of pressure from the source
Sound will dissipate through any medium as long as the particles in that medium can vibrate

39
Q

high pitch

A

high frequency low wavelength

40
Q

intensity/loudness

A

amount of energy/strength of vibrations - height of wave

41
Q

range of hearing for a young human adult

A

20-20,0000 Hz

42
Q

inner ear parts

A

cochlea and vestibule

43
Q

middle ear parts

A

tympanic membrane
ossicles
eustachian tube

44
Q

outer ear parts

A

pinna - amplifies and filters incoming sounds

ear canal - has hairs and wax on outer third

45
Q

mechanisms that amplify sound in middle ear

A

difference in size between tympanic membrane and oval window

lever action - ossicles act as little levers adding a small amount of amplification

46
Q

why does the middle ear amplify sound

A

transmission of sound from air to fluid-filled inner ear is inefficient due to impedance mismatch

47
Q

branchial arches in ear

A

First arch turns into mandible which gives rise to malleus and incus
Second arch gives rise to stapes

48
Q

describe the protective muscles in the middle ear

A

stapedius reflex and tensor tympani
they contract when ear is exposed to very loud sounds - there to stiffen the stapes so it does not vibrate and damage cochlea

49
Q

structure of eustachian tube

A

connects nasopharynx to middle ear

lined with mucosa

50
Q

function of eustachian tube

A

Keeps the air pressure in the middle ear space the same as the ambient atmospheric pressure - This is important to enable the tympanic membrane to vibrate

51
Q

describe conductive hearing loss

A

sound does not reach cochlea - inner ear still working but sound does not reach there
caused by:
• Ear canal – wax, foreign body, congenital atresia
• Tympanic membrane – perforation
• Ossicles – congenital fusion, damage from infection
• Middle ear space – fluid instead of air

52
Q

describe the vestibular apparatus

A

contains sensory structures for balance and head movements
utricle and saccule which are there for static position
semicircular canals are there for rotatory acceleration in three planes

53
Q

describe the scala media

A

contains endolymph

54
Q

where is perilymph

A

scala vestibuli and scala tympani

55
Q

structure of organ of corti

A

has a basilar membrane which the the hair cells sit on
tectorial membrane covers the hair cells
one row of inner hair cells and 3 rows of outer hair cells

56
Q

how does the organ of corti work

A

sound vibrations in scala vestibuli and scala tympani set up vibrations in basilar membrane
inner hair cells pick up vibrations on basilar membrane and send neural impulses along auditory nerve
outer hair cells are motile and change shape and stiffness when stimulated by the vibrations - acts as an amplifier to increase amount of vibration
as BM vibrates, stereocilia are bet against tectorial membrane - opens an ion channel - hair cell membrane is depolarised and NTs are released

57
Q

describe hair cell depolarisation and hyperpolarisation

A

tallest cilium is the kinocilium on hair cell
kinocilium moves away from sterocilia causing depolarisation
kinocilium moves towards sterocilium causing hyperpolarisation

58
Q

describe sensorineural hearing loss

A

the root cause lies in the inner ear or sensory organ (cochlea and associated structures) or the vestibulocochlear nerve

59
Q

loss of inner hair cells

A

no signal to brain

loss of hearing

60
Q

loss of outer hair cells

A

basilar vibration is insufficiently amplified
some loss of hearing
loss of discrimination - can hear speech but not understand it

61
Q

describe the travel of an impulse generated by a sound wave

A

first order neurons in spiral ganglion of the cochlea -> CN VIII -> synapse on juction of medulla and pons -> pons -> midbrain -> thalamus -> cortex -> temporal lobe

62
Q

what is the auditory nerve

A

one of two parts of CN VIII

63
Q

describe the anterior 2/3 of tongue

A

innervated by CN V and VII

tuberculum impar is the midline

64
Q

describe the tongue muscles

A

genioglossus, hyoglossus and styloglossus
suspended from mandible, hyoid and styloid bones
muscles work with palatoglossus to move tongue

65
Q

function of filiform papillae

A

rough surface of tongue for manipulation of food

66
Q

where are taste buds

A

scattered across tongue in fungiform papillae

67
Q

5 tastes and where they come from

A 
sour (acid, H+)
salty (Na+)
sweet (glucose)
bitter (coffee, beer, quinine, blue cheese, olives)
savoury/umami (glutamate)
68
Q

chorda tympani in tongue

A

branch of the facial nerve that originates from the taste buds in the front of the tongue, runs through the middle ear, and carries taste messages to the brain

69
Q

pathway of nerve impulses caused by taste

A

taste runs along lingual nerve and leave in chorda tympani which runs through middle ear to join facial nerve - runs with facial nerve to brainstem

70
Q

lingual nerve

A

branch of CN V (trigeminal)

71
Q

turbinates on nose

A

projections from either side of the nose with thick vascular mucosa to warm and humidify the air

72
Q

pathway of smell

A

odorant molecules in air dissolve in nasal mucus
odour receptor cells are then stimulated and axons pass through the little holes in cribiform plate up into olphactory bulb

73
Q

describe olfactory receptors

A

exist on dendrites of receptor cells

each receptor responds to more than one odourant and each odourant stimulates more than one receptor

74
Q

where does CN I project to

A

amygdala, hippocampus, parahippocampal gyrus

75
Q

what is congenital anosmia

A

lifelong inability to smell

can be assoicated with kallmans syndrome

76
Q

causes of anosmia

A 
base of skull fracture
covid 19
brain tumour
early sign of Alzheimer’s, Parkinson’s, MS
rhinosinusitis

Medicine phase 1 (14 decks)

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