Week 4 - Study Guide - Vision Flashcards
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
2
Q
Eyeball wall contains three tunics
A
Fibrous - outer
Vascular (Uvea)
Sensory - innermost
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
4
Q
Outer membrane on eye
A
Conjunctiva
5
Q
Another name for eyelids
A
palpabrae
6
Q
What part of the eye produces tears?
A
Lacrimal apparatus
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
8
Q
What drains the humors?
A
Venous sinus drains
9
Q
Outermost layer of the eye - Fibrous Tunic
A
Sclera - white part
Cornea - transparent
Sclera sinus drainage
10
Q
Middle layer of the eye -
Vascular Tunic
AKA - Uvea
A
has vascularity and nutritive purposes
- Choroid
- Ciliary bodies
- Ciliar ligaments
- Iris
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
12
Q
Ciliary Bodies
A
ring surrounding the lens
Helps control the shape of the lens by altering - that is the ciliary muscle
13
Q
Ciliary Zonal Ligaments
A
Attach to the lens
Controls the shape pf the lens
Can focus light
14
Q
Iris
A
color surrounding pupil
where light enters
AKA - diaphragm
Dilates and constricts
15
Q
Innermost layer of the eye - Sensory Layer
A
Retina
Photoreceptors
Optic Disc
(pigmented & Neural)
Where sensors exist
16
Q
Photoreceptors
A
Rods
Cones
17
Q
Rods
A
- Peripheral
- Dim light
- monochromatic
- Indistinct
- Broad image - no detail
18
Q
Vitreous Humor
A
- Main body of the eye
- Posterior
- Watery solutes
19
Q
Humor
A
Fluid sitting in the eye
Move humor through the posterior chamber and move towards the anterior chamber
20
Q
Aqueous Humor
A
- Anterior
- Produced by cells anterior to the ciliary body
21
Q
Sclera
A
White, tough, collagenous
posterior
Collagen fibers run in all directions
22
Q
Cornea
A
Anterior
clear
collagen in parallel to keep transparent
23
Q
What gives clarity?
A
- collagen fibers run parallel
- dehydrating the eye by -moving Na+ out
-creating a concentration gradient
Water will follow by osmosis
24
Q
What is accomodation in the eye?
A
allows for vision up close and far away
25
Iris
color surrounding the pupil where light enters and hits the retina
Dark - dilate - gather light - sympathetic
Light - constrict - reduce bright light
-parasympathetic
26
Cones
1. In front of the fovea centralis
2. Bright light
3. High acuity - lots of detail
4. Color vision
27
When light hits rods or cones --
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
28
Optic Disc
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
29
Pupillary Reflex
Parasympathetic
causing pupil constriction
consensual= response in both eyes
30
Ciliospinal reflex
Sympathetic
Causing pupil dilation
ipsilateral and not consensual
31
Salivary reflex
parasympathetic
32
Which has more specific control, sympathetic or parasympathetic?
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
33
Terminal Ganglia
Parasympathetic
end or near target organ
long pre-ganglionic axon
34
Cholinergic features
Ach
N/M
Nico- gate opens - depolarization
M- 2nd messenger system
inhibitory or excitatory
35
Adrenergic features
NE
Alpha/Beta
B1 - heart
B2 - BV of lungs, brain, heart
Alpha - BV of periphery, excitatory
36
Alpha
Constricts blood vessels of Periphery
Excitatory to smooth muscle - constriction
37
Remember that not all cranial nerves cross
Not all cranial nerves cross
38
Adrenergic
fiber type releases NE
39
Cholinergic
fiber type that releases Ach
40
Muscarinic
Ach receptor that involves a 2nd messenger
41
Nicotinic
Ach receptor that is always excitatory
42
Alpha
Sympathetic receptor on skin, mucosa, viscera
43
Beta
Sympathetic receptor on heart - B1
B2= airways, blood vessels of heart, brain and lungs
44
We have cones that are
Blue, Green, Red
45
Blood to Retina and Photoreceptor Distribution
Where the blood is coming from that feeds either the:
1. internal eye
2. External surface of the eye
46
Feeding the outer layer of the eye
Choroid -outer third (photoreceptors)
Central artery (inner 2/3)
(ganglion & bipolar cells)
47
Visual Acuity defined
Ability of a subject to discern details
48
Flat lens =
Distance vision
49
What actions flatten the lens
1. Ciliary muscles relax
2. Zonular ligaments pulled tight
3. Causing lens to flatten
to increase distance vision
50
What action rounds the lens?
1. Ciliary muscles contracted
2. Zonular ligaments slacken
3. Causing lens to round to increase close up vision
51
Refraction
Bending of light rays
52
Rods & Cones Similarities
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
Differences in Rods
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
Differences in Cones
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
Photoreceptor does
A specialized nerve that:
1. takes in light
2. converts it into a neural impulse
56
Photoreceptors send
only IPSPs
57
Bipolar cells send
only EPSPs
58
Ganglion cells send
only Action Potentials
59
Pure Dark
Signal transmission in the retina
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
Darkness to some light - what does the light do?
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
Rhodospin
Visual (chemical) pigment in rods made of protein
62
Rhodospin comes in two isomer forms
11-cis-retinal = In Dark
All-trans-retinal = In Low Light
63
In the dark, Rhodospin
Forms and accumulates
All-trans-retinal --> 11-cis-retinal
64
In the light, Rhodospin
Breaks down
11-cis=retinal --> all-trans isomer
Retinal and opsin separate (bleaching pigment)
65
When light hits rods
Rods will turn off and stop sending IPSPs
66
CIS =
kinked
67
trans =
straight
68
PHOTOTRANSDUCTION
in light
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
PHOTOTRANSDUCTION
in Dark
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
Visual Adaption
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
Hemifield
Visual field in front of you
72
Hemiretina
Lateral/Temporal
Lateral Hemiretina of left eye is perceiving visual information from right region of the hemifield
73
Hemiretina
Medial/Nasal
Medial Hemiretina of left eye is perceiving visual information from Left side of visual field
74
Visual Pathways:
Different parts of the visual field go to different locations
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
Left Hemifield
will eventually end up on Right Optic tract
crossover at optic chiasm
76
Right Hemifield
will eventually end up on Left Optic tract
crossover at optic chiasm
77
Temporal views crossover
Nasal views stay in same side
Temporal views crossover
Nasal views stay in same side
78
Scotoma
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
Right eye blind
Damage to R optic Nerve
80
Tunnel Vision
(temporal hemifield blind)
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
Left Hemifield Blind
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
Hemifield
Half of visual field
83
Damage to Right Optic Cord
Loss L half visual field in both eyes
84
Hemiretina
Half of the posterior of the eye
85
Damage to the L optic Nerve
Loss of vision in L eye
86
Damage to optic chiasm
Loss of peripheral vision
87
Damage to R nasal hemiretina
loss of peripheral vision of R eye
88
Give two differences & similarities between a stretch & a withdrawal reflex:
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
Somatic VS ANS
1. Both are motor pathways, leading to effectors
2. effectors are different
3. Differ in # of motor neurons
4. Voluntary/Involuntary
90
Para VS Sympa
1. Same # of motor neurons
2. Fiber types differ
3. Myelination same pattern
4. Effectors overlap
91
Which receptor converge to bipolar cells?
rods (600 to 1)
Large receptive field
excellent motion detection
not detail
92
Which receptor is non-converging
cones. (1:1:1)
cone --> bipolar cell --> ganglion
detailed, high resolution small receptive fields
93
Photoreceptors only send
IPSPs
94
Bipolar cells send only
EPSPs
95
Ganglion cells send only
APs
96
Light Adaptation
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
Dark Adaptation
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
