Ocular Physiology Flashcards
1
Q
What type of blinking is most common?
A
Spontaneous.
2
Q
How many blinks is normal per minute?
A
12-15
3
Q
What part of lid does spontaneous blinking?
A
palpebral
4
Q
Reflex blinking nerves
A
CN II dazzle and menis. CN V-irritation CN VIII-loud noises.
5
Q
What part of eye does reflex blinks?
A
palpebral
6
Q
Which is the only reflex that does not involve the cortex?
A
Dazzle. All other begin in the frontal lobe.
7
Q
What causes voluntary blinking
A
palpebral and orbital.
8
Q
Benign essential belpharospasms
A
Contractions of orbiculares oculi, procures, and corrugated.
9
Q
Bell’s phenomenon
A
Upward and out eye with forced closure
10
Q
Which glands can increase secretion with blinking?
A
Meiobomian
11
Q
What do accessory lacrimal glands do?
A
Basal or maintenance tears
12
Q
What does the main lacrimal gland do?
A
Reflex or emotional tearing
13
Q
Which glands help with lipid layers?
A
Meiobomian, Zeiss, Moll.
14
Q
Horners
A
Contractions on closure and shortens the cannaliculi
15
Q
How does blinking help tear film
A
Goes from lateral to medial
16
Q
How many eyelashes do we have
A
150 on top and 75 on bottom
17
Q
What is lipid layer made of
A
fatty acids, cholesterol, waxy esters.
18
Q
How do tears change with age?
A
Decrease in lysozyme and lactoferrin and decreased aqueous protection
19
Q
What does contact lens wear do?
A
Increases electrolyte and protein concentration due to tear evaportion
20
Q
How do tears change under closed eye conditions
A
Increases IA and serum albumin
21
Q
How are mucin layer unique
A
Capable of mixing with lipid and water.
22
Q
Where are goblet cells found?
A
Inferonasal fornix and bulbar conj (most temporal)
23
Q
What do goblet cells need for development
A
Vitamin A
24
Q
Bitot’s spots
A
foamy build up of keratin on the cornea. Caused by vitamin A deficiency.
25
Lipid soluble vitmins
DEAK
26
Antioxidants
ACE
27
Water soluble vitamins
B and C
28
What is TBUT evaluating
The tear film evaporation due to an inefficient lipid layer
29
What does the mucin layer interact with
glycocalyx of the epithelium.
30
Normal tear production per minuts
1 ul/min.
31
Normal tear film osmolarity
308
32
Main ions to osmolarity
Na and K
33
How does DES affect tear osmolarity
Increase is osmolarity
34
What kind of drops would you use with DES
hypotonic. More water.
35
Potassium concentration in tears
Very high! helps to maintain health of corneal epithelium.
36
Average pH of tears
7.45
37
pH of tears when sleeping
decreases
38
pH of tears with DES
increases due to increased osmolarity
39
What are most ophthalmic drugs
weak bases.
40
Stapedius muscles
Dampen sound. Innervated by CN VII
41
Vestibule
Linear VOR. Movements of head or body from side to side.
42
Semi-circular canals
Angular VOR. Rotation movements of the body or head.
43
Saccades
contralateral and FEF and SC. EX: Right FEF controls saccades to the left
44
Pursuits
ipsilateral parietal lobe. Right pursuit driven by right parental lobe.
45
VOR
Your body is moving!
46
How are the layers of the cornea in response to water
Epithelium: lipophilic, stroma: hydrophobic, endo: lipophilic.
47
UV c
200-290
48
UV B
290-320
49
UV A
320-400
50
What absorbs from 200-300
Cornea (epi and bowman).
51
What absorbs from 300-400
Lens
52
What absorbs from 300-350
vitreous
53
What absorbs above 400
retina
54
What vitamin helps the lens
Vitamin C
55
What does the precise spacing in the lens do?
Destructive interferance
56
Corneal desturgence
The relative dehydration of the cornea
57
Epithelium Pump mechanism
Na in and Cl, H20 and K+. Out. Has an Na/K ATPase pumps that puts NA in stroma and NA/K/CL cotransporter Will then pump K in aqueous and CL in epithelium which then leaves with H20.
58
Endothelium Pump Mechanism
Pumps NA in and Cl, water, and bicarbonate out. Use an NA/K ATPase pump.
59
Major factors in corneal desurgence
Na in and Cl, and H20 out. (bicarbonate in endo).
60
K+ factor in corneal dusurgence
The sensor.
61
Partial pressure of O2 in the eyes with open conditions
144 mm HG
62
How does eye get oxygen during closed eye conditions
Palpebral conj, aqueous humor
63
Critical PPO2 for the cornea
10-20 mm HG.
64
Transmisibility
DK/t. How much oxygen will diffuse over a given thickness.
65
Nutrition for cornea
glucose is low in tears but high in aqueous humor. Corneal epithelial cells can also store glycogen for mitosis.
66
How many days for cornea to regenerate
7-14 days.
67
Steps when trauma to cornea happens
Mitosis in basal stops, squamous cells migrate, mitosis increases rapidly.
68
How long for healing if BM is damaged
8 weeks
69
Why can corticosteroids and tetracyclines be used for RCE
MMPs degrade hemidesmosome formation and these drugs stop that from occurring and help formation
70
Which layers cannot regenerate
Bowman's and endo.
71
Which layer can regenreate
epithelium and descents.
72
Does the anterior or posterior lens change more in curvature with accommodation?
The anterior
73
What structure has the most protein in the body?
The lens.
74
How does the lens maintain it's water balance
Na/K ATPase pump. Na leaves and water follows.
75
Resurgence in Epithelium vs. lens
Epithelium pumps NA in and Cl and H20 out. Lens pumps Na out.
76
How does lens get energy?
Anerobic metabolism. Has lots of hexokinase.
77
What happens with diabetic cataract?
Excess sorbitol in the lens.
78
Glutathione
Good for the lens.
79
Absobic Acid
Vitamin C. Also protects from damage.
80
What layer of lens can do aerobic respiration
epithelium.
81
Why is there a large amount of lactate in the lens?
Large amount of anerobic metabolism
82
Which part of the lens has the sutures?
Fetal
83
Which part of the lens needs the greatest energy and nutrients?
Anterior epithelium (why it is good that it can do aerobic respiration)
84
What type of collagen is in the lens
Type IV.
85
Where is the lens capsule thickest
Front
86
What contributes to cataract formation
Decreases glutathione, decrease in crystallin factors, and an increase in Ca.
87
Which part of lens has the highest refractive index
The embryonic.
88
Aqueous humor secretion and age?
Decreases
89
Choroid has a high concentration of protein. Why?
To create a gradient that will absorb excess H20 from the retina and into the choroid
90
What type of collagen is the viterous
Type 2
91
Gag in the viterous
Hyaluronic acid.
92
Vitamin C in the viterous
Very high.
93
Metabolic function of the viterous
No metabolic function so instead acts as a metabolic buffer and storage area
94
Where in the vitreous is collagen highest
Near the base.
95
How does hyaluronic acid change with age
increases (liquidifaction)
96
Perfusion pressure
Parteries-Pveins
97
What are two factors causing resistance
Autonomic and autoregulation
98
what are two things that can autoregulate
ON axo flow and retina. Pericytes control this.
99
What does sympathetic cause
vasoconstriction
100
what does para cause
vasodilation
101
Ocular perfusion pressure
Diastolic pressure-IOP.
102
Critical closing pressure
The pressure where the blood vessel collapse and blood flow stops.
103
Transmural pressure
Pressure across the vessel wall. Pressure outside vs. inside vessel.
104
Does the sympathetic system affect retinal blood flow?
NO! DO not innervate the CRA past the lamina cribosa. Do innervate uvea though. If there is a sudden increase in BP then the sympathetic will constrict the uveal blood vessels to decrease flow
105
Parasympathetic system and retinal blood flow?
Parasmpathic is most prevalent in uveal tract. Minimal influence on choroidal and retinal blood flow. Causes vasodilation with drop in blood pressure
106
IOP must be ______ that the episcleral venous pressure
Greater. Allows outflow
107
IOP must be _____ than the ICP
Greater. Allows axoplasmic flow.
108
IOP must be _____ than the retinal and uveal arteries
Lower. Allow nutrients to be delivered
109
Which vessels in the uvea are fenestrated
MACI and choroidal capillaires
110
Blood supply in the fovea
Avascular so supplied by choriocapillaris
111
Blood retinal barrier
Blood vessels of retina and RPE
112
How does light absorption change the photopgigment
goest from 11-cis-retinal to all-trans-retinal.
113
Recycling of the photopigments
11-cis-retinal->all trans retinal-->all trans retinol-->RPE-->11 cis retinol-->11-cis retinal.-->photopigments
114
Dark Current
Na coming in and out. Depolarizes the photoreceptor
115
What happens with light
CGMP closes the Na channel and hyper polarization occurs and does not produce glutamate.
116
Gaba and Glycine
Inhibitory. Amacrine and horizontal.
117
Which cells are off cells
photoreceptors, off center bipolar, horizontal. All hyper polarize in response to light. Less glutamate
118
On center bipolar
Depolarizes in response to light. Normally inhibited by glutamate.
119
Off center bipolar
hyper polarize in response to light. Excited by glutamate so less=hyper polarize
120
Rod bipolar
Always ON. Depolarize to light.
121
Horizontal cells
Off cells. Hyper polarize to light. No center surround.
122
Amacrine cells
On center. Depolarize to light. Have center surround.
123
On center ganglions
synapse with on center bipolar and depolarize to light.
124
Off center ganglions
synapse with off center bipolar and hyper polarize to light.
125
Action potentials
All or nothing response-Amacrine and ganglion are AP. All others are not
126
Graded potentials
Determined by amount of photons absorbed. All but ganglion and amacrine.
127
Pyramidal motor pathway
complicated voluntary movements.
128
Medulla
Where most pathways cross. Above is contralateral. Below is ipsilateral.
129
Reticulospinal
Complex voluntary movement
130
Tectospinal
Uses the SC
131
Spinalthalamic
Hot pain.
132
Trigemothalamic
pain and hot from face.
133
Medial lemniscus
Touch, pressure, vibration.
134
SNS roles
vasodilation in skeleton muscle, dilates the bronchioles, increases blood glucose levels.
135
Preganglionic SNS
Release acetycholine
136
Post ganglionic SNS
Releases Norepinephrine
137
Which is the only gland innervated by preganlionic SNS
Adrenal gland
138
What does PSN release
acetylcholine for both
139
When do you use CT
bone, calcium, or emergency. Look at ca density.
140
When do you use PET
cancers. Looks at glucose uptake
141
When do you use MRI
soft tissue, look at mobile protons-more water-diseased tissue.
142
Where is the LGN located?
Thalamus.
143
Is LGN simply a rely station?
NO! Is is also a center for processing input from multiple sources and deciding what is sent to V1
144
Who does LGN receive input from?
Optic tract, SC, V1 (last two are feedback)
145
Which layers of LGN receive mango? Parvo? Konio?
Magno=1,2 Parvo=3-6 Konio=inbetween
146
Which layer are ispliateral in LGN
2,3,5
147
Which layers are contralateral in LGN
1,4,6
148
Where is the first area that binocular processing occurs?
V1
149
Medial to lateral in lgn
fovea->peripheral vision
150
Anterior to poster in LGN
inferior to superioer
151
Dorsal to vental LGN
Same spot in the VF
152
Optic radiations of inferior
Temporal lobe in meyer's loop
153
Optic radiation of supeior
Parietal lobe.
154
Parvo cells
Sensitive to red green, fine details, and slow motion but have a slower transmission speed
155
Magno cells
monochromatic and are most sensitive to fast movements and large details.
156
Visual Cortex
Striate cortex, boardman 17 or V1.
157
layer 4 of visual cortex
receives input from optic radiations. Have ocular dominance columns.
158
Layer 3 of visual cortex
Axons to other cortical layers
159
Layer 6 of V1
Sends feedback back to LGN
160
Function of V1
examine basically features before relaying information to more complex processing centers (v2-v5)
161
Layer 5 and 6 of V1
subcortical areas (SC, Thalamus, midbrain, pons)
162
V2-V5
Responsible for complex processing. Includes IT (what) and MT (where)
163
SC
Receives input from V1 and fibers that exit the optic tract. Controls saccades, visual orientation, and foveation.
164
FEF
Only receives information from V1. Does near response and saccades.
165
Simple Cells of the Visual Cortex
respond to orientation of stimuli. Have elongated center surround
166
Complex cells of the visual cortex
Respond to motion and orientation. NO center surround.
167
Hypercomplex cells
Process combined input from multiple cells
168
How does V1 process information
heriarchialy.
169
EOG
Measures the health of the RPE
170
Arden ratio
EOG. The ratio of light peak to dark trough
171
What arden ratio do we want
Above 1.80
172
ERG
Looks at activity of outer retinal layers. No ganglion cell layers.
173
A wave
negative and photorceptors
174
B-wave
positive and bipolar and muller
175
C-wave
positive and RPE
176
How to isolate rod function on EOG
Blue flash with a slow flicker in a dim background
177
How to isolate cone function on EGO
Red flash with a fast flicker in a bright background.
178
Pattern ERGs
Target the ganglion cels
179
VEP
Latency of brain activity to visual stimulus
180
Normal VEP
100 sec
181
What always causes anisocoria
efferent pathway problem
182
Near response
FEF gets input from V1 and synapse with EW (no pretectacl)
183
SNS and EW
Sympathetic fibers inhibit the EW from constant parasympathetic features.
184
Goldman measurement
Based on elasticity of the cornea. Based on cornea thickness of 520.
185
Thick corneas on goldman
Overestimate
186
NCT
Time
187
Pascal
Contour. Do not take corneal thickness into account
188
Average IOP
15
189
How to decrease IOP w/o topical
Exercise, drink beer, marijuana.
190
When is IOP highest
330-530 AM
191
How often is the total volume of the aqueous replaced
every 100 minutes
192
Uveoscleral is Presure _____ while corneal scleral is Pressue _______
independent dependent
193
What are two conditions that can increase episcleral venous pressure
Spurge-Weber and arteriovenous fistulas.
194
Osmolarity of the aqueous
Slightly hyper osmotic to plasma due to bicarbonate.
195
How can aqueous be made? What is the main one?
Diffusion, ultrafilteraion, active secretion. Active secretion.
196
Pumps that make aqeuous
NA/K atpase pump pumps NA into the posterior chamber. Bicarbonate is also made and causes water and Cl to follow.
197
What can cause covering of the TM
Diabetes, CRVOs, Uveitis, hyphema
198
What can cause injury to the TM
Fuchs heterochromatic iritis, glaucomatocyclic crisis (trabeculitis that can cause damage), angle recession glaucoma.
199
Occlusion of the TM
Pseduoedcofiliative glaucoma or Pigment dispersion glaucoma.
