Lecture 14: Special Senses: Vision Flashcards
1
Q
What anterior portion of the eye contains what fluid
A
Aqueous humor
2
Q
The posterior portion of the eye contains what fluid
A
Vitreous
3
Q
___ is a clear specialization of the sclera
A
Cornea
4
Q
Where are photoreceptors located
A
Retina
5
Q
What nerve innervates the optic nerve
A
CN II
6
Q
What nerve innervates dorsal rectus, ventral rectus, ventral oblique, medial rectus, ciliary, levator palpebrae, iris and sphincter muscles
A
CN III
7
Q
What nerve innervates dorsal oblique
A
CN IV
8
Q
What nerve innervates the lateral rectus and retractor bulbi
A
CN VI
9
Q
What layer has melanin in the epithelial layer that absorbs light
A
Choroid layer
10
Q
Do diurnal or nocturnal species have a more pronounced choroid layer
A
Dinurnal
11
Q
What is the tapetum lucidum
A
Reflective layer behind the retina
12
Q
Do diurnal or nocturnal species have a more pronounced tapetum lucidum
A
Nocturnal
13
Q
Where does light focus in the retina
A
Fovea centralis
14
Q
Who has a better developed fovea centralis, diurnal or nocturnal species
A
Diurnal
15
Q
What species have multiple fovea
A
Birds
16
Q
which layer of the retina is closest to the vitreous fluid
A
Inner retina
17
Q
Which layer of the retina is closest to the choroid layer
A
Outer retina
18
Q
What are the four neurons in the retina
A
Bipolar, horizontal, amacrine, and ganglion cells
19
Q
Describe the pathway of light through the retina and what cells are involved
A
- Lights act on the rods and cones which then synapse with bipolar cells
- Horizontal cells are interacting at site of synapse between rods/cones and bipolar cells
- Bipolar cells synapse with ganglion cells
- Amacrine cells are interacting at site of synapse with bipolar and ganglion cells
- Ganglion cells send axons through optic disk to form optic nerve
20
Q
Which photoreceptor is sensitive to low light
A
Rods
21
Q
Which photoreceptor functions best in daylight
A
Cones
22
Q
Which photoreceptor has high acuity
A
Cones
23
Q
Which photoreceptor has low acuity
A
Rods
24
Q
Which photoreceptor utilizes rhodopsin
A
Rods
25
Which photoreceptor utilizes opsin-retinal
Cones
26
Which photoreceptor is achromatic
Rods
27
Which photoreceptor sees color
Cones
28
Which photoreceptor has their cells converge on a single bipolar cell
Rods
29
Which photoreceptor does not converge on a single bipolar cell
Cones
30
Which photoreceptor is concentrated in the peripheral retina
Rods
31
Which photoreceptor is concentrated in the fovea
Cones
32
Describe how light is transduced to chemical energy
1. In the dark there is an influx of Na+ ions
2. Photons convert cis-retinal to all trans-retinal
3. Trans retinal attached rhodopsin activate cGMP phosphosdiesterase
4. CGMP decreases
5. Na+ channels start to close
6. Membrane hyperpolarizes
7. More light, greater response, less transmitter released- results in graded potential
33
What ion is influxed in the dark
Na+
34
Is the cis or trans-retinal form formed in response to light
Trans
35
Which photoreceptor is more sensitive to structural detail
Cones
36
What type of wiring allows cones to have greater structural detail
One to one wiring between cone and bipolar cell leads to high spatial discrimination
37
What is the trade off for cones and their high spatial discrimination
Requires ample light
38
How many opsins do most mammals have
Two
39
How many opsins do primates have
3
40
What species vision is tetrachromatic, four opsins that absorb red, green, blue and UV
Avian
41
What species have UV sensitive cones
Lizards, turtles and fish
42
What cells in the retina provide lateral transmission
Horizontal and amacrine
43
Light influences the adjacent portion of the retina it does not hit and therefore ___contrast, provides ____sensitivity, and ___discrimination
Increased contrast, directional sensitivity, and color discrimination
44
T or F: the direction of light travels in the same direction as visual processing
False, direction of light travels from the inside out, whereas the direction of visual process travels from outside in
45
___inhibition increases contrast
Lateral
46
Describe how lateral inhibition works
1. Ganglion cells stimulated if photoreceptors of well defined field are illuminated BUT their response is inhibited if neighboring photoreceptors are excited
2. Horizontal cells respond by sending an inhibitory signal to neighboring ganglion cells
47
What does the retino-geniculo-striate pathway do
Conscious visual perception of form, movement, color, orientation and depth
48
___ cells project to the ipsilateral and contralateral visual cortex
Ganglion cells
49
Describe the pathway from the optic tract to the occipital cortex
1. Fibers in the optic tract proceed to the thalamus
2. In the thalamus they synapse on the lateral geniculate nucleus
3. They then travel and innervates the occipital cortex
50
Where do axons of the optic tract synapse in the thalamus
Lateral geniculate nucleus
51
Injury to the left hemisphere will affect the left or right visual field
Right
52
What is eye position
Convergence of two eyes to focus objects on the fovea, follow objects, fixate the visual field
53
What is accommodation of the eye
Lenses adapt focal length
54
What reflex are you testing when you test the eyes ability to follow objects and fixate on the visual field
Vestibulo-ocular reflex
55
What is strabismus
Misalignment of the eyes, object is projected on different parts of the retina and causes double vision
56
What is exotropia
Lateral displacement
57
A patient with left lateral displacement could have a lesion where
Left oculomotor nucleus (CN3)
58
What is esotropia
Eye turned inward
59
Accommodation is altering of the shape of the lens by action of the ___muscle
Ciliary
60
Ciliary muscle contraction results in…
Relaxation of tension of the lens causing the lens to be more curved
61
Describe the pathway of accommodation
1. Retina
2. Optic nerve CN II
3. Lateral geniculate nucleus
4. Visual cortex
5. Superior colliculus
6. Oculomotor nucleus
7. PNS motor efferent to ciliary muscle via CN III
62
is iris sphincter muscle controlled by PNS or SNS
PNS
63
Describe the pathway of constriction via iris sphincter muscle
1. Optic tract
2. Pretectal nucelus
3. Preganglionic fibers in EW nucleus
4. Synapse in ciliary ganglion
5. Postganglionic innervation to iris sphincter muscle- eye constricts
64
Is the iris dilatory muscle controlled by SNS or PNS
SNS
65
Describe the pathway to the iris dilator muscle
1. Preganglion neurons begin in thoracic segments of spinal cord
2. Course to superior cervical ganglion
3. Postganglionic fibers innervates dilator muscles
66
What CN controls the iris sphincter muscle
CN III
67
What CN controls the iris dilator muscle
CN VII
68
What does the retina-tectal pathway do
Provides pupillary reflex and reflex orientation of the eyes to visual targets
69
Describe the pathway of the retina-tectal pathway
1. Ganglion cells
2. Pretectal nucleus
3. E-W nucleus
4. oculomotor CN III
70
What does the retino-hypothalamic pathway
Provides light to set physiological rhythms in suprachiasmatic nucleus
71
Describe the eye blink reflex: touch the cornea/eyelid
1. Free nerve endings in the cornea stimulate CN V
2. CN V terminates in spinal trigeminal nucelus
3. Reticular formation interneurons send bilateral axons to facial nucleus
4. Facial motor neurons CN VII send axons down the facial nerve to obicularis oculi which close eyes
72
What CN are activated in eye blink reflex, which is afferent and efferent
CN V: afferent
CN VII: efferent
73
What is the pathway of the menace response test
1. Visual stimulus relayed via CN II
2. Travel to thalamus—> occipital cortex
3. Motor neurons stimulate the ipsilateral facial nerves CN VII and activate orbicularis oculi to close eye
74
Which CN are activated in menace response, which is afferent which is efferent
CN II: afferent
CN VII: efferent
75
The menace response tests potential damage to __
Cortex, cerebral lesions may result in loss of menace response
76
Light stimulates the ___ pathway
Retino-tectal pathway
77
Describe the pupillary light reflex
1. Retinal ganglion cells project to Pretectal nucleus via CN II
2. Pretectal to E-W nucleus which give rise to preganglionic PNS
3. Travel on CN III to ciliary ganglion
4. Innervate sphincter muscle of iris
78
Case ex: PLR
1. Shine light into left eye: No direct or consensual response
2. Shine light into right eye:
Normal direct and consensual response
Where is the lesion?
CN II, optic tract
79
Case ex 2: PLR
1. Shine light in left eye:
No direct response, normal consensual response in right
2. Shine light in right eye:
Normal direct and no consensual response
Where is the lesion
CN III
80
Case #3: PLR response- animal is blind in left eye
1. Shine light into left eye, normal direct and consensual response
2. Shine light in the right eye
normal direct and consensual response
Where is the lesion
Right cerebral hemisphere
81
What are some symptoms of horners syndrome
Miosis, ptosis, enophthalamus, prolapsed nictating membrane
82
Is a prolapsed nictating membrane cause by insufficient SNS or PNS innervation
SNS
