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5 senses Flashcards

1
Q

visible light range

A

400 - 750nm (blue - red)

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2
Q

role of optical component of the eye?

A

collects and focuses light onto the plane of the retina

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3
Q

role of neural component of the eye?

A

converts light energy into patterned changes of membrane potential that the brain can decode

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4
Q

refractive power of the eye

A

approximately 60 diopters

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5
Q

focal point of eye based on the approximate refractive power

A

approximately 17mm beyond the lens

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6
Q

what are the 3 processes of the near response?

A

Accommodation, constriction, convergence

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7
Q

what is the activity of parasympathetic on ciliary muscles/zonular fibres/lens when looking at distant objects?

A

low parasympathetic activity therefore ciliary muscle relaxed, and zonular fibres are pulled taut which flattens the lens

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8
Q

what is myopia and its treatment?

A

NEARSIGHTEDNESS eyeball too long, therefore, light focused ahead of the plane of the retina, corrected using convex lens

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9
Q

what is hypermetropia and its treatment?

A

FARSIGHTED, eyeball too short, objects focused beyond scope of retina. corrected with convex lens, which increases focal power to bring focal point forward

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10
Q

what is astigmatism and its treatment?

A

curvature of cornea and/or lens is aspherical, therefore different amount of refraction in different planes. corrected with cylindrical lens

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11
Q

what is presbyopia and its treatment?

A

age-related loss of accommodation. Lens lose elasticity, as a consequence near point recedes from approx. 10cm at 20 years to 80cm at 60 years. corrected with convex (reading glasses)

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12
Q

what is cataract?

A

lens becomes opaque due to cells within lens dying. lens can be surgically removed and replaced with plastic one. ability to accommodate is lost post-surgery.

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13
Q

constriction of the pupil - dilated

A
  • decreased periphery

- when object is close

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14
Q

constriction of pupil - undilated

A
  • increased periphery

- object further away

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15
Q

what is accommodation in near response?

A

contraction/relaxation of ciliary muscle to alter lens shape and change refractive power

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16
Q

what is constriction of pupil?

A

improved depth of focus, fewer optical abberations including edges of lens

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17
Q

what is convergence of eyes?

A

objects remain in register on corresponding parts of the two retinae

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18
Q

what is the retina important?

A

the retina is part of the brain, contains photoreceptors at the back and ganglion cells and axons in front for processing.

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19
Q

how does info flow between photorecptors and ganglion cells?

A

via interneurons

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20
Q

function of rods (photoreceptor) and their approximate number per retina?

A
  • function in low-level light (night vision)
  • not colour sensitive
  • 120 million per retina
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21
Q

function of cones (photoreceptor) and their approximate number per retina?

A
  • function in high light levels (day/twilight vision)
  • 8 million per retina
  • 3 types: red, blue and green
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22
Q

what makes photoreceptors light sensitive?

A

the presence of photopigments

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23
Q

the 2 components of the photopigment

A
  1. ) a membrane-spanning protein called opsin
    - rods have rhodopsin
    - cones have S, M, or L photopsin
  2. ) a chromophore called retinal (vitamin A derivative)
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24
Q

what colour is S photopsin?

A

Blue

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25
what colour is M photopsin?
green
26
what colour is L photopsin?
Red
27
phototransduction in the dark
- retinal is non-activated (inactive 11-sic isoform) - intracellular cGMP is high - cGMP gated channels open - Na influx into blood cells - photoreceptor (rods) depolarized to - 30mV - lots of glutamate released onto bipolar cells
28
phototransduction in the light
- light energy/photons - retinal changed to active all-trans isoform - trans- retinal activates a G protein called transducin - transducin activates cGMP phosphodiesterase, breaking down cGMP to normal GMP - less cGMP therefore cGMP gated channels close - photoreceptor hyperpolarised to - 60mV
29
consequences of vitamin A deficiency
- night blindness/ eyes unable to adapt to low light conditions - severe problem in developing countries - 1st symptom is dry eyes
30
retinal processing
- photoreceptors communicate with retinal interneurons via GRADED changes in membrane potential - retinal interneurons may be excitatory or inhibitory - retinal ganglion cells have long axons (form optic nerve), fire AP, and send visual info to centres in brain for visual processing
31
at night, intracellular cGMP levels are...?
cGMP levels high at night
32
when do cGMP channels open?
cGMP gated channels open in absence of light
33
when is retinal activated? (active c11-cis isoform)
retinal is activated with the presence of light
34
what happens when cGMP gated channels open?
Na influx, photoreceptor depolarised, and lots of glutamate released onto bipolar cells
35
S-photopsin
blue, most sensitive to short wavelengths
36
M- photopsin
green, sensitive to medium wavelengths
37
L- photopsin
red, sensitive to long wavelengths
38
4 common diseases that cause damage to optic nerve or retina
- glaucoma - diabetes - alzheimers - parkinsons
39
what causes inherited colour blindness?
genes encoding the M and L opsins are on the X chromosome.
40
what is the 'blind spot'?
the optic disc where axons leave retina, no photoreceptors at this point.
41
what is sound?
pressure waves in the atmosphere
42
frequency/pitch range of human hearing
between 20 and 2000Hz
43
threshhold of human hearing approximate start and 'end'
0 and 145 dB. decible scale = log scale.
44
3 parts of inner ear
- cochlea - semicircular canals - vestibule
45
3 parts of outer ear
- auricle - external auditory canal - tympanic membrane
46
ossicles of middle ear
- stapes - incus - malleus
47
What parts of the ear are air-filled?
inner and outer ear are air-filled.
48
how does sound transduction work from outer to middle ear?
- sound waves cause the tympanic membrane to vibrate | - vibrations are then transmitted via the ossicles
49
what happens to the vibrations after they are transmitted via the osscicles?
- vibrations then cause a change in P in fluid of scala vestibuli - this fluid displacement causes displacement in cochlear duct
50
what does the displacement in the cochlear duct then cause?
- a displacement in the basilar membrane thus the organ of corti
51
what does a displacement in the basilar membrane/organ of corti create?
creates shear forces, forcing the stereocilia on hair cells to bend
52
deflection of stereocilia causes...
- opening of chemically gated ion channels | - K+ enters hair cells from endolymph causing depolarization
53
(depolarization once K+ has entered hair cell causes...
- depolarization opens Ca2+ channels and Ca2+ enters hair cell
54
increased concentration of Ca2+ in hair cell causes...
- increased Ca2+ causes neurotransmitter release onto the cochlear nerve
55
what happens after neurotransmitter release on cochlear nerve?
- synapse on cochlear nucleus in brainstem - axons project through lateral lemniscus to medial geniculate body - axons then project to primary auditory cortex (R & L)
56
how is pitch/frequency discrimination determined?
discrimination of pitch is determined by activity in hair cells at specific points on basilar membrane
57
how is intensity of sound determined?
loudness is determined in the number of impulses per second in auditory nerve fibres (change in depolarisation causes change in Ca2+ influx and consequent vesicle release)
58
deafness by infection is caused by ?
build up of fluid which dampens tympanic membrane and prevents correct sound transmission
59
what is conduction deafness?
impaired sound transmission through outer or middle ear
60
where on basilar membrane do hair cells respond to high frequency?
at base of basilar membrane, where hair cells are taught
61
where on basilar membrane do hair cells respond to low frequency?
at apex of basilar membrane where hair cells are loose
62
what is the stimuli of the vestibular system?
stimuli is angular and linear accelerations of head
63
what are the 5 vestibular receptors in each ear?
- 3 x semicircular canals | - 2 x otolith organs
64
what do semicircular canals transduce?
semicircular canals rotational accelerations of head
65
what do otolith organs transduce?
otolith organs transduce linear accelerations of the head
66
what do the horizontal semicircular canals detect?
horizontal semicircular canals detect shaking of head in TRANSVERSE plane
67
what do anterior semicircular canals detect?
anterior semicircular canals detect nodding in SAGGITAL plane
68
what do posterior semicircular canals detect?
posterior semicircular canals detect rotation in CORONAL plane
69
what is the ampulla and where is it located?
the ampulla is the dilated end of a semicircular duct in a semicircular canal.
70
describe the cupula
the cupula is a gelatinous structure that sits in the ampulla which holds the hair cell and stereocilia in place
71
what happens in left side semicircular canals when head moves in left direction? (vv)
when left moves to left, the hair cells are bent towards the tallest end,
72
moving left causes endolymph in ampulla to move....
moving left causes endolymph to move right
73
when head moves in the opposite direction to semicircular canal side it causes...
moving in opposing direction causes bending toward the smallest stereocilia.
74
what does bending toward the tall end of stereocilia cause?
towards tall end opens mechanically gated ion channels thus depolarization (stimulation)
75
what does bending toward the short end of stereocilia cause?
towards short end shuts mechanically gated ion channels thus hyperpolarization (inhibition)
76
what does the resting discharge rate of the vestibular nerve allow?
detect increase/decreases in AP firing thus hair cells can signal in 2 directions.
77
what is the orientation of the utricle and its hair cells when standing?
utricle is approximately horizontal, and its hair cells within it are oriented vertically
78
what is the orientation of the saccule and its hair cells when standing?
saccule is approximately vertical, and its hair cells within are oriented horizontally
79
what does the movement of otoconia cause?
movement of otoconia causes bending of hair cells
80
what is the central vestibular pathway?
- central vestibular pathway: axons project to vestibular nuclei in brain stem - info then used to stabilise eyes, head and maintain balance
81
what does the oculomotor nucleus do?
oculomotor nucleus stabilises images on the retina
82
What is an acoustic neuroma?
abnormal growth of schwann cells
83
what is motion sickness and how do you treat it?
- a mismatch between visual and vestibular info | - treated with MeclozineHydrochloride (sea legs)
84
what is vertigo?
disease affecting the vestibule or its afferent fibres
85
what is 'bedspins"?
- alcohol/ethanool infiltrates cupula and lowers density causing it to float, thus bending hair cells.
86
what are taste buds made up of?
complex cluster of 50-100 columnar epithelial cells (type 1, 2 and 3)
87
type 1 columnar epithelial cells in taste bud
glial cells, maintain homeostasis
88
type 2 columnar epithelial cells in taste bud
umami, sweet, bitter
89
type 3 columnar epithelial cells in taste bud
sour, salty
90
taste buds are innervated by what nerves?
- chorda tympani - lingual - trigemina - glossopharyngeal nerves
91
where do the afferent fibres of the tastebud nerves synapse? (what happnens after?)
synapse in medulla | info is then relayed to the thalamus then to cortex
92
what taste cells have G-protein mediated signal transduction pathways? (draw it out)
type 2 taste cells have G-protein mediated signalling | sweet, bitter, umami
93
structure of sweet taste receptor?
homodimer or type 1 receptor
94
structure of bitter taste receptor?
monomer of type 2 receptor
95
structure of umami taste receptor?
heterodimer of type 1 receptor
96
what taste cells require Non G -protein signalling transduction pathways? (draw it out?)
type 3 cells have non G protein signaling | sour and salty
97
where does olfactory signal transduction occur?
olfactory signal transduction occurs in receptor cilium of olfactory cells
98
what enzyme embedded in plasma membrane of olfactory cilia is activated upon inhalation/entry of odourant?
adenylyl cyclase is activated.

phty251 (6 decks)

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