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BIO 232 > Week 4 - Study Guide - Vision > Flashcards

Week 4 - Study Guide - Vision Flashcards

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1
Q

What is the percentage of receptors in the body has to do with the eye?

A

70% receptors is they eye
AND
1/2 the cerebral cortex

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2
Q

Eyeball wall contains three tunics

A

Fibrous - outer
Vascular (Uvea)
Sensory - innermost

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3
Q

Additional separation in the eye by the leans creates two cavities with humors

A

Aqueous humor - water - anterior

Vitreous - posterior
maintains pressure and shape

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4
Q

Outer membrane on eye

A

Conjunctiva

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5
Q

Another name for eyelids

A

palpabrae

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6
Q

What part of the eye produces tears?

A

Lacrimal apparatus

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7
Q

What are Extrinsic eye muscles?

A

-Muscles - not of lens or iris
-But attach to outer surface of the eye

^ have individual innervation and can be diagnostic

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8
Q

What drains the humors?

A

Venous sinus drains

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9
Q

Outermost layer of the eye - Fibrous Tunic

A

Sclera - white part
Cornea - transparent
Sclera sinus drainage

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10
Q

Middle layer of the eye -
Vascular Tunic
AKA - Uvea

A

has vascularity and nutritive purposes

  1. Choroid
  2. Ciliary bodies
  3. Ciliar ligaments
  4. Iris
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11
Q

Choroid

A

POSTERIOR
1. covers the inside of the sclera
2. Pigment helps absorb additional light rays
3. Helps supply blood to the structures of the eye

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12
Q

Ciliary Bodies

A

ring surrounding the lens

Helps control the shape of the lens by altering - that is the ciliary muscle

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13
Q

Ciliary Zonal Ligaments

A

Attach to the lens
Controls the shape pf the lens

Can focus light

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14
Q

Iris

A

color surrounding pupil
where light enters

AKA - diaphragm

Dilates and constricts

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15
Q

Innermost layer of the eye - Sensory Layer

A

Retina
Photoreceptors
Optic Disc

(pigmented & Neural)

Where sensors exist

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16
Q

Photoreceptors

A

Rods
Cones

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17
Q

Rods

A
  1. Peripheral
  2. Dim light
  3. monochromatic
  4. Indistinct
  5. Broad image - no detail
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18
Q

Vitreous Humor

A
  1. Main body of the eye
  2. Posterior
  3. Watery solutes
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19
Q

Humor

A

Fluid sitting in the eye

Move humor through the posterior chamber and move towards the anterior chamber

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20
Q

Aqueous Humor

A
  1. Anterior
  2. Produced by cells anterior to the ciliary body
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21
Q

Sclera

A

White, tough, collagenous
posterior

Collagen fibers run in all directions

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22
Q

Cornea

A

Anterior
clear
collagen in parallel to keep transparent

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23
Q

What gives clarity?

A
  1. collagen fibers run parallel
  2. dehydrating the eye by -moving Na+ out
    -creating a concentration gradient
    Water will follow by osmosis
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24
Q

What is accomodation in the eye?

A

allows for vision up close and far away

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25
Q

Iris

A

color surrounding the pupil where light enters and hits the retina

Dark - dilate - gather light - sympathetic

Light - constrict - reduce bright light
-parasympathetic

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26
Q

Cones

A
  1. In front of the fovea centralis
  2. Bright light
  3. High acuity - lots of detail
  4. Color vision
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27
Q

When light hits rods or cones –

A

Goes from:
1. Photoreceptor
2. Bipolar Neurons
3. Ganglion cells
4. Opti Nerve

  1. Light enters and hits rods or cones
  2. Move forward to eye
  3. Bipolar neurons which will
  4. send signal even more forward to
  5. ganglion cells
  6. Which will create the axon that
  7. makes up the optic nerve
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28
Q

Optic Disc

A

Blind spot

Where the optic nerve and blood vessels enter and exit the eye

Area at the back of the retina that does not have receptors

Nerve is exiting the eye

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29
Q

Pupillary Reflex

A

Parasympathetic

causing pupil constriction

consensual= response in both eyes

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30
Q

Ciliospinal reflex

A

Sympathetic

Causing pupil dilation

ipsilateral and not consensual

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31
Q

Salivary reflex

A

parasympathetic

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32
Q

Which has more specific control, sympathetic or parasympathetic?

A

Parasympathetic

Has a pathway to a specific neuron for a specific response

Not sympathetic because:
Adrenal Gland messes everything up
E/NE one shot at survival
not specific
survival mode - dump resources

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33
Q

Terminal Ganglia

A

Parasympathetic
end or near target organ
long pre-ganglionic axon

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34
Q

Cholinergic features

A

Ach
N/M

Nico- gate opens - depolarization

M- 2nd messenger system
inhibitory or excitatory

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35
Q

Adrenergic features

A

NE
Alpha/Beta
B1 - heart
B2 - BV of lungs, brain, heart
Alpha - BV of periphery, excitatory

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36
Q

Alpha

A

Constricts blood vessels of Periphery

Excitatory to smooth muscle - constriction

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37
Q

Remember that not all cranial nerves cross

A

Not all cranial nerves cross

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38
Q

Adrenergic

A

fiber type releases NE

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39
Q

Cholinergic

A

fiber type that releases Ach

40
Q

Muscarinic

A

Ach receptor that involves a 2nd messenger

41
Q

Nicotinic

A

Ach receptor that is always excitatory

42
Q

Alpha

A

Sympathetic receptor on skin, mucosa, viscera

43
Q

Beta

A

Sympathetic receptor on heart - B1

B2= airways, blood vessels of heart, brain and lungs

44
Q

We have cones that are

A

Blue, Green, Red

45
Q

Blood to Retina and Photoreceptor Distribution

A

Where the blood is coming from that feeds either the:
1. internal eye
2. External surface of the eye

46
Q

Feeding the outer layer of the eye

A

Choroid -outer third (photoreceptors)

Central artery (inner 2/3)
(ganglion & bipolar cells)

47
Q

Visual Acuity defined

A

Ability of a subject to discern details

48
Q

Flat lens =

A

Distance vision

49
Q

What actions flatten the lens

A
  1. Ciliary muscles relax
  2. Zonular ligaments pulled tight
  3. Causing lens to flatten
    to increase distance vision
50
Q

What action rounds the lens?

A
  1. Ciliary muscles contracted
  2. Zonular ligaments slacken
  3. Causing lens to round to increase close up vision
51
Q

Refraction

A

Bending of light rays

52
Q

Rods & Cones Similarities

A
  1. Photoreceptor cells
  2. Found in retina
  3. Absorb light
  4. Converts light into signals that result in phototransduction
  5. Assist in vision in presence of light
  6. Synapse with Bipolar cells
  7. Chemical process that supports phototransduction is similar
53
Q

Differences in Rods

A
  1. Found at the periphery of the retina
  2. Low light vision
  3. More rod cells than cone cells (120 million)
  4. Rod cells triggered by a single photon of light
  5. one type of protein pigment in rod cells - Rhodospin
  6. Sensitive to scattered light and direct light
  7. Absent in fovea
  8. Loss of rod cells cause night blindness
54
Q

Differences in Cones

A
  1. Cones found in the front of the fovea of the retina
  2. Vision in bright light
  3. Color vision
  4. Number of cones are less than rods (6 million)
  5. Large number of protons required to trigger cone cells
  6. 3 different types of photopsin - red, blue, green
  7. cones only sensitive to direct light
  8. Concentrated in fovea
    Loss of cone cells causes legal blindness
55
Q

Photoreceptor does

A

A specialized nerve that:
1. takes in light
2. converts it into a neural impulse

56
Q

Photoreceptors send

A

only IPSPs

57
Q

Bipolar cells send

A

only EPSPs

58
Q

Ganglion cells send

A

only Action Potentials

59
Q

Pure Dark
Signal transmission in the retina

A

Darkness:
1. Rods will be firing IPSPs
2. You see nothing
3. Photoreceptors are saying there is nothing to see
4. Going to inhibit Bipolar cells from sending any signals because there is nothing to see

60
Q

Darkness to some light - what does the light do?

A
  1. It hyperpolarizes photoreceptors
  2. Turns photoreceptors off
  3. If photoreceptors are off - they stop sending inhibitory signals
  4. NOW Bipolar cells start to depolarize with an EPSP
  5. When they send EPSPs to the ganglion cells
  6. It will lead to an action potential
  7. Send signal to optic nerve
  8. To the brain
  9. Now instead of being in total darkness - see nothing- you are in low light - see something
61
Q

Rhodospin

A

Visual (chemical) pigment in rods made of protein

62
Q

Rhodospin comes in two isomer forms

A

11-cis-retinal = In Dark

All-trans-retinal = In Low Light

63
Q

In the dark, Rhodospin

A

Forms and accumulates

All-trans-retinal –> 11-cis-retinal

64
Q

In the light, Rhodospin

A

Breaks down

11-cis=retinal –> all-trans isomer

Retinal and opsin separate (bleaching pigment)

65
Q

When light hits rods

A

Rods will turn off and stop sending IPSPs

66
Q

CIS =

A

kinked

67
Q

trans =

A

straight

68
Q

PHOTOTRANSDUCTION
in light

A
  1. Rhodospin = cis –> trans
  2. G protein transducin is activated
  3. transducin activates PDE (enzyme catalyzes a reaction)
  4. PDE converts cGMP –> GMP
  5. Drop in cGMP –> channel closes - rod stops sending IPSPs to Bipolar cells
  6. Hyperpolarization
69
Q

PHOTOTRANSDUCTION
in Dark

A
  1. cGMP build up over time
  2. cGMP binds and opens channel of the rod
  3. Na+ and Ca2+ influx depolarizes!!!
  4. Rod sends its specific type of signal - IPSPs
70
Q

Visual Adaption

A
  1. Light Adaption is quicker
    dark to light
    -Visual acuity improves over 5-10 minutes
  2. Dark Adaption slower
    Light - Dark
    -Retinal sensitivity increases 20-30 minutes
71
Q

Hemifield

A

Visual field in front of you

72
Q

Hemiretina

Lateral/Temporal

A

Lateral Hemiretina of left eye is perceiving visual information from right region of the hemifield

73
Q

Hemiretina

Medial/Nasal

A

Medial Hemiretina of left eye is perceiving visual information from Left side of visual field

74
Q

Visual Pathways:
Different parts of the visual field go to different locations

A

Contralateral projections

Result of optic chiasm and the hemifields

Some will cross over and some will stay on the same side

Ipsilateral and contralateral organization

75
Q

Left Hemifield

A

will eventually end up on Right Optic tract

crossover at optic chiasm

76
Q

Right Hemifield

A

will eventually end up on Left Optic tract

crossover at optic chiasm

77
Q

Temporal views crossover

Nasal views stay in same side

A

Temporal views crossover

Nasal views stay in same side

78
Q

Scotoma

A

Portions of the visual field that are non-functional

There has been damage somewhere in the visual pathway causing very specific losses of what the L and R eye can actually see

79
Q

Right eye blind

A

Damage to R optic Nerve

80
Q

Tunnel Vision

(temporal hemifield blind)

A

Take out optic chiasm

  1. each eye losing most peripheral field of vision
  2. See in only the medial region

Think horse and blinders

81
Q

Left Hemifield Blind

A

Take out an Optic Tract
(After the Optic chiasm)

  1. Loss of vision on right nasal field
  2. Loss of vision on left hemifield
82
Q

Hemifield

A

Half of visual field

83
Q

Damage to Right Optic Cord

A

Loss L half visual field in both eyes

84
Q

Hemiretina

A

Half of the posterior of the eye

85
Q

Damage to the L optic Nerve

A

Loss of vision in L eye

86
Q

Damage to optic chiasm

A

Loss of peripheral vision

87
Q

Damage to R nasal hemiretina

A

loss of peripheral vision of R eye

88
Q

Give two differences & similarities between a stretch & a withdrawal reflex:

A
  1. Stretch - direct connection of sensory & motor neuron (monosynaptic), painful stimuli VS muscle spindle initiates.
  2. Both are automatic; go through spinal cord & are ipsilateral
89
Q

Somatic VS ANS

A
  1. Both are motor pathways, leading to effectors
  2. effectors are different
  3. Differ in # of motor neurons
  4. Voluntary/Involuntary
90
Q

Para VS Sympa

A
  1. Same # of motor neurons
  2. Fiber types differ
  3. Myelination same pattern
  4. Effectors overlap
91
Q

Which receptor converge to bipolar cells?

A

rods (600 to 1)

Large receptive field
excellent motion detection
not detail

92
Q

Which receptor is non-converging

A

cones. (1:1:1)
cone –> bipolar cell –> ganglion

detailed, high resolution small receptive fields

93
Q

Photoreceptors only send

A

IPSPs

94
Q

Bipolar cells send only

A

EPSPs

95
Q

Ganglion cells send only

A

APs

96
Q

Light Adaptation

A

Dark –> Light
1. pigment broken down
2. pupils constrict
3. rod function stops
4. cones & neurons rapidly adapt
5. Visual acuity in 5-10 minutes

97
Q

Dark Adaptation

A

Light –> Dark
1. Reverse light adaptation
2. Cones stop functioning
3. Pupils dilate
4. 11-cis retinal builds up
Retinal sensitivity increases over 20-30 minutes

BIO 232 (63 decks)

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