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Biomed2 > Sense Organs > Flashcards

Sense Organs Flashcards

1
Q

What is the vestibulocochlear nerve

A

Main Nerve supply in the inner ear - 8th cranial nerve

Refers to the two main bones inner ear
Vestibule = involved in balance
Cochlear = involved with hearing

Contains vestibular fibre nerve branches
& cochlear fibres

Nerve is located within the brainstem (space between pons / medulla oblongata)

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2
Q

3 sections of the ear

A
  1. Outer
  2. Middle
  3. Inner
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3
Q

3 main bones in the middle ear

A

Smallest in the body
Have tiny symovial joints (which sometimes can degenerate over time)

Malleus (hammer)
Incus (anvil)
Stapes (stirrup) - smallest

() = what they look like

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4
Q

What is the eustachian tube

A

Connects the middle ear to the nasopharynx

Helps equalise pressure in middle ear

Aka ‘pharyngotympanic’ tube

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5
Q

3 main parts of the outer ear

A
  1. Auricle/Pinna
  2. External auditory canal
  3. Tympanic membrane (eardrum)
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6
Q

What is the pinna

A

Aka auricle
Flap of elastic cartilage, visibile part of the ear on side of head

Ridges in the skin helps trap soundwaves & directs them into the auditory canal

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7
Q

What is the tympanic membrane

A

Ear drum
Thin, semi-transparent partition between external auditory canal & middle ear. Lined with simple cuboidal epithelium, elastic & collagen fibres

Transmits sound from outer ear to the auditory ossicles.
Converts sound waves into mechanical vibration

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8
Q

What is the middle ear

A

A small air filled cavity in the temporl bor containing 3 main bones

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9
Q

What is the stapedius muscle

A

Tiny muscle that connects to the stapes to dampen large vibrations & prevent excessive movement

(Supplied/innovated by facial nerve e.g sounds in bells palsey)

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10
Q

Role of the middle ear

A

3 bones transmit sound in the form of vibration from the tympanic membrane to the oval window which connects to cochlea

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11
Q

What connects the middle ear to inner

A

Oval window (connected to stapes)

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12
Q

What makes up the inner ear labyrinth

A

Consists of outer bony labyrinth that encloses inner membranous labyrinth

Contains
3 semicircular canals & vestibule (responsible for balance)
Cochlea (hearing)

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13
Q

What fluid does the labyrinth contain

A

Perilymph & endolymph

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14
Q

What are stereocilia

A

Microscopic hair cells in epithelial tissue that give information about sound
Receptors for hearing that extend into the endolymph

(Sensory cells are topped with 40-80 cilia each)

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15
Q

How does the cochlea interpret sound

A

Waves of fluid move the stereocilia which creates an electrical impulse that sends information into the cochlea nerve

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16
Q

Pitch of soundwaves measured in

A

Hertz (Hz)

Higher frequency = higher pitch

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17
Q

Volume of sound measured in

A

Decibels (dB)

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18
Q

Decibel scale

A

Near total silence = 0dB
10x more = 10dB
100x more = 20dB
1000x more = 30dB

85dB or more prolonged = damage
Around 140 = instant pain

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19
Q

What is white noise

A

A constant noise that contains all different frequencies of sound (mix of different sound waves)
Background noise the brain ignores

Can be used to mask other sounds (privacy enhancers, sleep aids, tinnitus masking)
White noise with headphones can aid concentration

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20
Q

Role of the esutachian tube

A

Closed tube but can open for air to equalise pressure between middle ear & atmosphere ‘ear popping’
Also drains mucous & common route for infection

Yawning & swallowing contracts the neck muscles opening the tube

Essential air can escape middle ear otherwise damage would occur with pressure changes

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21
Q

Why are middle ear infections more common inchildren

A

The eustachian tube is more horizontal & shorter, less distance for virus & bacteria

As age gets longer & more vertical

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22
Q

Which structures provide info on head position aka balance

A

Semi-circular canals & vestibule
Plus a dense layer of calcium carbonate crystals aka ‘otolithic membrane’

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23
Q

Role of the otolithic membrane

A

Dense layer of calcium carbonate crystals that extend over & rest on the stereocilia

Any change in head position causes movement in the perilymph & endolymph which causes the membrane to bend hair cells & stimulate sensory nerve endings > action potential is then transmitted to the cerebellum (via CN VIII)

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24
Q

What can cause vertigo

A

Where calcium carbonate crystals break off from the membrane and land amongst the stereocilia causing nerve signals to be overstimulated&raquo_space; feeling of movement when not

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25
Q

How is balance in the cerebellum regulated

A

Input from:

  • vestibular (from inner ear)
  • visual feedback (from eyes)
  • proprioceptors in skeletal muscles, joints & surrounding ligaments (dorsal columns heavily myelinated - info travels from feet)
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26
Q

Balance/cerebellar functioning test

A
  • nose to finger test
  • clapping hand test
  • ataxia (wide leg stance)
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27
Q

What cranial nerve is the eye supplied by

A

Cranial nerve 2
Optic

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28
Q

Role of the iris

A

Coloured part of the eye, controls amount of light reaching the retina by adjusting pupil size

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29
Q

Role of the lens

A

Located behind the pupil & further focuses light (along with the cornea - both bend light rays)

30
Q

What is the vitreous humour

A

Area of fluid behind the lens that helps lubricate & keep eye open

31
Q

Eyebrow function

A

Prevent sweat/other material from entering eye

32
Q

Function of eyelashes/eyelids

A

Help to spread secretions over eye & protect

33
Q

Conjunctiva function

A

Thin transparent mucous membrane of columnar epithelial cells lining the internal eyelids & anterior eyeball - protects cornea

Eyelid margins secrete oily material to delay tear evaporation

34
Q

Lacrimal apparatus function

A

Tearduct - trigeminal nerve (CN V) controls
Tears protect eye from infection (contain IgA & lysozymes) & lubricate & have an emotional function

35
Q

What is light

A

Part of electromagnetic spectrum

Wavelengths are 400-700nanometers (nm) & exhibit colours depending on their length

White light = combination of all

36
Q

How is light focused onto the retina

A
  • refraction of the light rays
    (Images focused on the retina are inverted & left-right reversed too. Brain learns to coordinate this)
  • accommodation of the eyes
  • changes lens size & pupil size (contraction & relaxation of iris)
37
Q

What is refraction

A

Describes the bending of light rays
Occurs when light moves from one substance to another which have a different density

38
Q

What is ‘accomodation’

A

Changing the diameter of the lens

39
Q

What perception needs greater refraction

A

Close percpetion - tires the eyes
Ciliary muscle contracts, reducing suspensory ligament tension & lens becomes more convex

40
Q

What perception needs lesser refraction

A

Distant perception
Ciliary muscle relaxes, increasing tension on suspensory ligaments & lens gets flatter

41
Q

What are the circular muscles of the iris

A

Smooth muscle that constricts the pupil
Parasympathetic stimulates these fibres

42
Q

What are the radial muscle fibres of the iris

A

Smooth muscle that dilates the pupil
Sympathetic stimulates the fibres contraction

43
Q

What is eyeball convergence

A

Medial movement of two eyeballs so that both are directed towards the object
Extra-ocular muscles move the eyes in coordination under autonomic control

Closer the object, greater the eye rotation (cross-eyes eventually)

44
Q

What is diplopia

A

Double vision caused by incomplete convergence of the eyeballs (2 images sent to brain)

45
Q

What is the optic chiasma & where is it located

A

Where the optic nerve switches sides/crosses over in the brain

Is located next to the pituitary gland - hence tumours can cause ‘tunnel vision’

46
Q

What is the retina

A

Inner layer of the eye, lining 3/4 of posterior of the eyeball
Beginning of visual pathway

47
Q

What is used to view optic nerve & blood vessels

A

Ophthalmoscope

Can identify pathologies/nerve damage/brain tumour
Eg MS, diabetes

48
Q

What is the optic disc

A

Location where the optic nerve exits the eyeball & blood vessels enter/exit
‘Blind spot’ (no cone or rod cells)

49
Q

What 2 cells are found in the retina

A

Rod cells (120 million)

Cone cells (60 million)

50
Q

What are rod cells

A

Allow us to see in dim light but dont provide colour
Provide black, white & greyscale

51
Q

What are cone cells

A

Produce colour vision through combinations

3 types:
Blue, red, green

52
Q

What is the macula lutea

A

Yellowish spot at exact centre of retina
With fovea in the centre

53
Q

What is the fovea centralis

A

Small depression in centre of the macula lutea that contains only cone cells
Is the area of highest visual activity

54
Q

What are photopigments

A

Transmembrane proteins within the discs of rod and cone cells
When light hits the photopigment it changes shape initiating an action potential

Once activated, a photopigment must then be regenerated/restored

55
Q

What vitamin are photopigments derived from

A

Vitamin A in the form of retinal which binds to protein ‘opsin’

Pigmented layer of the retina stores a large quanitity of vitamin A which contributes to the regeneration of rod cells

56
Q

Dietary forms of vitamin A

A

Preformed = animal origin eg liver, egg yolk (excess can be toxic)

Precursors (metabolised to retinal in the intestines aka regulated absorption) = carotenoids (also powerful antioxidants) eg carrots, sweet potato, squash, mango, leafy greens

57
Q

Light adaptation

A

Emerging from dark to light, eyes adjust quite quickly
Adapts in seconds by decreasing sensitivity
Cones must regenerate photopigments, this can happen as quick as within first 8 minutes

58
Q

Dark adaptation

A

Moving from light to dark sensitivity takes eyes longer to adjust, increasing slowly
Rods must regenerate photopigments which takes much longer than cones

59
Q

What is the olfactory epithelium

A

Nose contains over 10-100 million receptors for olfaction within a tiny area (5cm2)

60
Q

What is in the olfactory epithelium

A
  1. Olfactory receptors: neurons attached to cilia. Respond to chemical stimulus of odorants by producing an action potential (up CN 1)
  2. Supporting cells: provide physical support, nourishment & help detoxify chemicals
    & olfactory glands that secrete mucous to trap odorants
  3. Basal cells: stem cells that continually divide to produce new receptors
61
Q

How long do olfactory recptors live

A

Around 1 month

62
Q

What nerve involved in smell

A

CN 1
Olfactory nerve

63
Q

How do olfactory receptors extend to cranial nerve

A

Nerve axons extend Through the cribriform plate of the ethmoid bone which then extends into the temporal lobe of the brain

Some axons project into the limbic system (emotion)

64
Q

Olfactory adaptation

A

Has a low threshold and only a few molecules need to be present to detect smell

Decreased sensitivity to odours occurs rapidly - adapt by 50% in first second - odours can seem 80% less powerful after a few minutes of exposure

Aim of adaptation is to protect from danger if harmful scent

65
Q

Cells involved in gustation

A

Chemicals are dissolved in saliva which stimulates chemoreceptors
Formed of 8 muscles controlled by CN 12 - hypoglossal (purely motor)

  1. Gustatory receptor cells
  2. Basal cells
  3. Supporting cells
66
Q

Lifespan of gustatory receptor cells

A

Live around 10 days

67
Q

How many taste buds in an adult

A

10,00 taste buds in adult, most on tongue but some on soft palate, pharynx & epiglottis

68
Q

types of tongue papillae

A
  1. Circumvallate papillae - largest, V-shaped found at back of tongue
  2. Fungiform - mushroom shaped, present all over tongue, contain about 5 taste buds each
  3. Foliate papillae - located in small trenches at lateral margins of tongue, most degenerate in childhood (used for breastfeeding/process of)
  4. Filiform papillae - tactile receptors help tongue move food/feel textures
69
Q

5 tastes

A

Sour, sweet, salty, bitter, umami

Taste impaired when dry mouth
Sense of taste triggers salivation & gastric juices

Responsiveness to taste is present in all areas of tongue

70
Q

Area of brain taste information goes

A

Gustatory nucleus in the medulla oblongata & some into the limbic system

71
Q

Nerves involving taste

A

Facial nerve (CN 7)
Glossopharyngeal nerve (CN 9)

72
Q

Nerves involving tongue sensation/movement

A

Trigeminal nerve
Glossopharyngeal nerve
Vagus nerve

Biomed2 (9 decks)

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