Vision/retina

Front 1

the image projected onto the retina is ____

Back 1

upside down

Front 2

layers of the retina?

Back 2

Front 3

what's the fovea look like? what doesn't it have?

Back 3

Fovea: there’s no axons no cell bodies..you’ve made the light path as clear as possible (least distortion)-->highest-acuity vision

Front 4

cellular components of retina

Back 4

Front 5

difference bw rods and cones?

Back 5

Disks in outer segmentdisks for surface area…capturing light
Have molecules that transduce light

Rods have more disks-->they function in dark…so that’s why they have more disks to capture as much light as possible


RODS
Scotopic: Low light levels
Monochrome: Single wavelength

CONES
Photopic: High light levels
Color vision: Three wavelengths

Front 6

Cones are less sensitive to light than the rod cells in the retina (which support vision at low light levels), but allow the perception of color.
Because humans usually have three kinds of cones, with different _____, which have different response curves, and thus respond to variation in color in different ways, they have trichromatic vision.

Back 6

photopsins

Front 7

what the photoreceptor distribution of the retina?

Back 7

cones concentrated in the middle....rods decrease in the retina's periphery

Front 8

when photoreceptors are activated, they become depolarized/hyperpolarized

Back 8

hyperpolarized!
opp of what you would accept

in the dark, they are activated..

Front 9

photoreceptor membrane potential is a balance bw

Back 9

Front 10

in the dark, which of the 2 currents dominate?

Back 10

Front 11

in the light, what happens to the currents in the photoreceptor

Back 11

Front 12

how is light transduced in photoreceptors?

Back 12

Light captured by rhodopsin (which is an G-protein associate receptor)….transducin (G-protein) activates cGMP phopodiesterase-->dec cGMP--> closing up cGMP-gated Na+ channels

Front 13

what is this?
what family of proteins does it belong to?
what molecule is it associated with?

Back 13

rhodopsin

G-protein coupled receptor

it's associated with the G-protein transducin

Front 14

“As a chromophore, ____ has covalently bound in its inactive dark state ____, which isomerizes after photon capture to an _____ This initial structural change within the chromophore binding pocket is propagated to the cytoplasmic surface of the receptor, enabling the docking and activation of downstream elements of the signal transduction cascade, as G protein, kinases, and arrestin.”

Back 14

rhodopsin

11-cis retinal

all-trans geometry.

Front 15

Set up center-surround receptive field properties bymodulating photoreceptorpotentials
“Integrate” light signalsover a variable area

Back 15

Front 16

Midget retinal ganglion cells project to the ______ layers of the ______These cells are known as midget retinal ganglion cells, based on the small sizes of their dendritic trees and cell bodies. About 80% of RGCs are midget cells in the parvocellular pathway.

They receive inputs from relatively few rods and cones. In many cases, they are connected to midget bipolars, which are linked to one cone each. They have slow conduction velocity, and respond to changes in color but respond only weakly to changes in contrast unless the change is great. They have simple center-surround receptive fields, where the center may be either ON or OFF while the surround is the opposite.

Back 16

parvocellular

lateral geniculate nucleus.



Midget Ganglion Cell
Red/Green
Small RFs
Central visual field
Spatial opponency

Front 17

Parasol retinal ganglion cells project to the _____layers of the lateral geniculate nucleus. These cells are known as parasol retinal ganglion cells, based on the large sizes of their dendritic trees and cell bodies. About 10% of retinal ganglion cells are parasol cells in the magnocellular pathway. They receive inputs from relatively many rods and cones. They have fast conduction velocity, and can respond to low-contrast stimuli, but are not very sensitive to changes in color. They have much larger receptive fields which are nonetheless also center-surround.

Back 17

magnocellular

Front 18

tell me the pathway of aqueous humor?

Intraocular pressure is a function of production of liquid aqueous humor by the ___body of the eye and its drainage through the _____. Aqueous humor flows from the _____ into the ____ CHAMBER, bounded posteriorly by the lens and the zonule of Zinn and anteriorly by the iris. It then flows through the pupil of the iris into the ____CHAMBER, bounded posteriorly by the iris and anteriorly by the cornea. From here the TRABECULAR NETWORK drains aqueous humor via ____
into scleral plexuses and general blood circulation.

In open angle glaucoma there is reduced flow through the trabecular meshwork;

in angle closure glaucoma, the iris is pushed forward against the trabecular meshwork, blocking fluid from escaping.

Back 18

ciliary

trabecular meshwork

CILIARY BODY

POSTERIOR

ANTERIOR

SCHLEMM'S CANAL

Front 19

treatment for glaucoma?

Back 19

Front 20

2 types of glaucoma?

Back 20

Open angle= reduced drainage through canal. Not painful.

Closed angle= iris pressing against trabecular meshwork, blocking fluid from draining. Painful.


angle =angle bw the iris and the cornea

Front 21

how to decrease aqueous humor production?

Back 21

Activation of Beta1 receptors increases aqueous humor production.
--Timolol (beta blocker) will decrease aqueous humor production

Beta agonists will make things worse

Alpha2 agonists (negative feedback, so decreased sympathetic tone) will decrease activation of beta receptors and therefore also decrease aqueous humor production

Front 22

how to increase drainage?

Back 22

A dilated pupil restricts outflow, a constricted pupil increases outflow.
---Parasympathetics constrict pupil
---Sympathetics (via alpha1 receptor) dilate pupil

Alpha1 blockers

Cholinomimetics (pilocarpine) or AchE inhibitors (physostigmine)

Alpha1 agonists (phenylephrine) and muscarinic antagonists (atropine) dilate pupil -> make things worse

Front 23

the optic radiation includes what 2 parts?

Back 23

Myer's loop (goes through temporal lobe)

and the part that goes through parietal lobe



If Meyer's loop is lesioned, the vision loss is superior; if the parietal path is lesioned, the vision loss is inferior.

Just remember MEYER= SUPERIOR VISUAL FIELD
PARIETAL PATH= INFERIOR VISUAL FIELD
Top retina (inferior visual field)goes in the parietal lobe…(shorter path)

Bottom retina (superior visual field) goes in the temporal lobe (longer path..more susceptible to damage)

Front 24

the optic radiation includes what 2 parts?

Back 24

Myer's loop (goes through temporal lobe)

and the part that goes through parietal lobe



If Meyer's loop is lesioned, the vision loss is superior; if the parietal path is lesioned, the vision loss is inferior.

Just remember MEYER= SUPERIOR VISUAL FIELD
PARIETAL PATH= INFERIOR VISUAL FIELD
Top retina (inferior visual field)goes in the parietal lobe…(shorter path)

Bottom retina (superior visual field) goes in the temporal lobe (longer path..more susceptible to damage)

Front 25

draw the visual field of each eye (the circles):

name of defect:

can be caused by:

Back 25

Front 26

Central Scotoma

caused by:

Back 26

Optic Neuritis

macular degeneration

Front 27

Back 27

glaucoma

Front 28

draw visual fields of both eyes (seriously!)
name of lesion:

can be caused by:

Back 28

Front 29

visual fields of both eyes:
name of defect:

can be caused by:

Back 29

Front 30

visual field of both eyes:

name of lesion:

can be caused by

Back 30

Front 31

Back 31

Front 32

Back 32

Front 33

Back 33

Front 34

In the human fovea the ratio of ganglion cells to photoreceptors is close to ___;

Back 34

1

almost every photoreceptor has one ganglion cell receiving data from it. That is why it has little loss of sensory data, thus it is the area of the eye where most details can be seen.

Starting at the outskirts of the fovea, however, rods gradually appear, and the absolute density of receptors progressively decreases.

The human fovea has a high concentration of cone photoreceptors. The centre of the fovea is the foveola - about 0.2 mm in diameter - where only cone photoreceptors are present and there are virtually no rods

Front 35

The fovea is the center most part of the ____ .It is the center of the eye's sharpest vision and the location of most color perception.

Back 35

macula

Front 36

how many cones?

Back 36

6 million

Front 37

how many rods?

Back 37

120 million

Front 38

output pathways from the retina?

Back 38

Front 39

cells of V1?

Back 39

Front 40

phototransduction?

Back 40

Front 41

receptor fields of ganglion cells? what is the type?

Back 41

center-surround

Front 42

types of cells in the retina?

Back 42

Front 43

light pathway:

start from light and end in primary visual cortex-->dorsal/ventral streams

Back 43

Light => cornea (focus) => aqueous humor => pupil => lens (adjustable focus) => vitreous humor--> photoreceptors (rods, cones) at the back of the retina (outer nuclear layer)--> bipolar cells (inner nuclear layer) => ganglion cells; M, P, K cells sending axons to...-->optic nerve->LGN (thalamus)->optic radiation (2 parts, Myer's loop + parietal pathway)-->V1 (primary visual cortex aka striate cortex, = Brodmann area 17)-->dorsal/ventral stream

Front 44

Which movement does NOT utilize MLF? With head still, Looking at your..

(a) R leg (b) L arm (c) L eyebrow (d) nose

Back 44

nose

Front 45

Light in L eye: only L pupil contracts. Light in R eye, BOTH pupils contract
Motor or sensory deficit? Where? (a) Motor nucleus (b) motor axon (c) CN II (d) E-W

Back 45

E-W

Front 46

Fovea –
-spot on retina corresponding to center of visual field
- has the highest visual acuity, highest density of ____
- lots of cones => great daytime/color vision, poorer nighttime vision
- overrepresented (size-wise) in post. visual cortex (analogous to fingertips in S1)

Back 46

photoreceptors

Front 47

what are opsins?

Back 47

-proteins that determine the spectum of light selectivity to which a photoreceptor responds

- Retinal (from vitamin A) is the light sensing component
- G Protein Coupled, activates cGMP phosphodiesterase [PDE]
- cGMP gated ion channels let in Na/Ca/Mg, these are active in the dark
- activation of cGMP PDE => decrease in cGMP => close channels

- thus, light causes a DECREASE in neurotransmitter release

Front 48

Rhodopsin consists of the protein moiety ___ and a reversibly covalently bound cofactor,

Back 48

opsin

retinal

Front 49

All ganglion cells are ____until the optic nerve
(maximize light getting through to photoreceptors)

Back 49

unmyelinated

Front 50

what's the optic disk?

Back 50

Front 51

The LGN receives information directly from the ascending______ via the optic nerve and from the reticular activating system.

Back 51

retinal ganglion cells

Front 52

how many layers of the LGN? with which ganglion cells do they correspond?

Back 52

6 layers

- 1-2 are Magnocellular (two largest layers at bottom)
- 4-6 are Parvocellular
- Intralaminar Layers are Koniocellular
- Layers 1, 4, 6 from contralateral eye
- Layers 2, 3, 5 from ipsilateral eye


[Can I C with two I’s Closed?]

Front 53

Visual cortex = primary visual cortex +

Back 53

extrastriate visual cortical areas such as V2, V3, V4, and V5.

Front 54

Primary Visual Cortex aka___Cortex, V1, Area

Back 54

Striate

17

Front 55

where's our blind spot?

Back 55

Front 56

the dorsal and ventral stream pathways?

Back 56

Front 57

The ventral stream begins with V1-->V2,-->V4 --> temporal lobe

"___ Pathway", is associated with form recognition and object representation. It is also associated with storage of long-term memory.(Trees > forest)
-input from all three cell types
-Less concerned with position in space or orientation

Back 57

What (as in vat?? for ventral stream)

Front 58

Damage to ventral stream?

Back 58

Agnosia (can’t recognize objects)
--- Proposagnosia – inability to recognize faces

ventral stream= vat pathway= form recognition and object representation

Front 59

MLF is the main pathway that connects the ____ and ____nuclei with the nuclei controlling the extraocular muscles (3, 4,6)

Back 59

vestibular
cochlear

MLF yokes the cranial nerve nuclei III, IV and VI together, and integrates movements directed by the gaze centers (frontal eye field) and information about head movement (from cranial nerve VIII).

It is an integral component of saccadic eye movements as well as vestibulo-ocular and optokinetic reflexes.
It also carries the descending tectospinal tract and medial vestibulospinal tracts into the cervical spinal cord, and innervates some muscles of the neck and upper limbs.

Front 60

______ is paralysis of the ciliary muscle of the eye, resulting in a loss of accommodation

Back 60

Cycloplegia

Front 61

______ is a condition in which the eyes are not properly aligned with each other.

Back 61

Strabismus

Front 62

_____is a form of strabismus, or "squint", in which one or both eyes turns inward

Back 62

Esotropia

Front 63

is the medical term used when the vision in one of the eyes is reduced because the eye and the brain are not working together properly. The eye itself looks normal, but it is not being used normally because the brain is favoring the other eye. This condition is also sometimes called lazy eye. .

Back 63

Amblyopia

Amblyopia is a developmental problem in the BRAIN, NOT an organic problem in the eye (although organic problems can induce amblyopia which persist after the organic problem has resolved). The part of the brain corresponding to the visual system from the affected eye is not stimulated properly, and develops abnormally. (recall the 'critical period')

Front 64

The center-surround receptive field organization allows ganglion cells to transmit information not merely about whether photoreceptor cells are exposed to light, but also about the differences in firing rates of cells in the center and surround. This allows them to transmit information about contrast. The size of the receptive field governs the spatial frequency of the information: ____ receptive fields are stimulated by high spatial frequencies, fine detail; ____receptive fields are stimulated by low spatial frequencies, coarse detail.

Back 64

small

large

Front 65

Frontal eye fields (FEF) is a gaze center in the _____that directs horizontal gaze _____


Paramedian pontine reticular formation (PPRF) is a gaze center in the ____that directs horizontal gaze ______
• Lesions in the frontal lobe causes gaze to look towards the lesion (the opposite FEF is unopposed)
• Lesions in the brainstem causes gaze to look away from lesion (the opposite PPRF is unopposed)

Back 65

frontal cortex, contralaterally

brainstem , ipsilaterally.

Front 66

Frontal eye fields projects directly to the _____PPRF

thus, Frontal eye fields (FEF) directs (horizontal) gaze contralaterally

Back 66

contralateral

Front 67

what connects the abducent and the oculumotor nuclei---imp for gaze coordination

Back 67

MLF!

medial longitudinal fasciculus

Front 68

____ is a type of strabismus in which one or both eyes turn inward, while

____ is a type of strabismus in which one or both eyes turn outward. If congenital and not corrected, due to the critical period, either can lead to _____.

Back 68

Esotropia

exotropia


ambylopia

Front 69

PUPILS

unequal pupils, at rest without stimuation, the pupil size in the one eye is different than in the other.

Back 69

anisicoria:

Front 70

PUPILS
No direct or consensual reflex, but DO have accommodation-convergence intact. Seen in neurosyphilis (last stage of untreated syphilis).

Back 70

Argyll-Robertson pupil

Front 71

PUPILS
Dilated pupil, reacts sluggishly to light, but better to accommodation.

Back 71

Adie pupil:

Front 72

Raised ICP leads to _____(uncus herniates across tentorium), CNIII compressed, creating a fixed and dilated pupil. Also, eye is positioned down and out" due to unopposed action of CN IV and CN VI.

Back 72

transtentorial uncal herniation:

Front 73

PUPILS

Afferent limb of reflex is damaged. Diagnosed with swinging-flashlight test, by which a light is shined in DAMAGED pupil: pupils do not constrict. Shine light in INTACT pupil: both pupils constrict fully.

Back 73

Marcus-Gunn pupil

Front 74

Horner syndrome

name 4 symptoms

Back 74

1. miosis (pupil CONSTRICTION. remember, sympathetics cause mydriasis -- pupil DILATION -- but, it you LOSE sympathetics, you get miosis).
2. Anisocoria -- this means 'unequal pupils.' This can happen in myriad diseases, and can even be normal. Because the lesion happened on one side (the side that his tumor is compressing on his sympathetic trunk), you would expect that pupil to be constricted, and the other to be normal, therefore, the patient has anisocoria.
3. anhidrosis (lack of sweating) on the side of the lesion, due to sympathetic loss. Hyperhidrosis is EXCESSIVE sweating, and would NOT happen in a loss of sympathetics.
4. ptosis (eyelid droop): drooping upper eyelid from loss of sympathetic innervation to the Müller (superior tarsal) muscle.

Front 75

Horner syndrome is due to a deficiency of _____ activity. The site of lesion to the sympathetic outflow is on the _____ side of the symptoms. The following are examples of conditions that cause the clinical appearance of Horner's syndrome:
• First-order neuron disorder: Central lesions that involve the hypothalamospinal pathway (e.g. transection of the cervical spinal cord).
• Second-order neuron disorder: Preganglionic lesions (e.g. compression of the sympathetic chain by a lung tumor).
• Third-order neuron disorder: Postganglionic lesions at the level of the ______ (e.g. a tumor in the cavernous sinus).

Back 75

sympathetic

ipsilateral


internal carotid artery

Front 76

If someone has impaired sweating above the waist affecting only one side of the body, yet they do not have a clinically apparent Horner's syndrome, then the lesion is just below the _____ ganglion in the sympathetic chain.

Back 76

stellate

Front 77

There are two common 'MS' visual lesions:

Back 77

optic neuritis and INO

Front 78

name the artery that supplies:
Optic chiasm/tract

Back 78

ACA and ICA

Front 79

name the artery that supplies

LGN

Back 79

PCA and anterior choriodal (most often off ICA)

Front 80

what supplies the optic radiations:

Back 80

MCA

Front 81

what supplies V1:

Back 81

PCA

Front 82

which artery supplies the occipital pole (absolute tip of occipital lobe):

Back 82

MCA and PCA

Front 83

Name the artery that supplies:

Optic chiasm/tract:
LGN:
optic radiations:
V1:
occipital pole (absolute tip of occipital lobe):

Back 83

Optic chiasm/tract: ACA and ICA
LGN: PCA and anterior choriodal (most often off ICA)
optic radiations: MCA
V1: PCA
occipital pole (absolute tip of occipital lobe): MCA and PCA

Front 84

PCA infarct
What can be lost?

Back 84

- The LGN is spared by the fact that the anterior choroidal can supply blood.
- But, he still loses a large part of V1. This produces a contralateral homonymous hemianopia.
- But, the macular/foveal region of the occipital lobe is 'rescued' or 'spared' by the fact that it gets blood from the MCA in addition to the PCA. Therefore, when there is a contra homonymous hemianopia, there is also macular sparing, and the region of highest visual acuity (macula and fovea are intact).

Front 85

MCA infarct would affect what?

Back 85

Since the MCA supplies the optic radiations, and they together (Meyer and parietal loop) produce a contralateral homonymous hemianopia, then that is the lesion: contralateral homonymous hemianopia (and includes the macula/foveal area as well).

Front 86

what's this?

Back 86

blind spot aka scotoma

Front 87

pituitary tumor: compression of medial optic chiasm produces_____vision, called_____

Back 87

tunnel
bitemporal hemianopia

Front 88

t/f

a lesion of the optic tract, LGN, or visual pathway to V1 produce SAME deficit: contra homonymous hemianopia

Back 88

true

Front 89

The fovea defines the center of the retina, and is the region of highest visual acuity. The fovea is directed towards whatever object you wish to study most closely - this sentence, at the moment. In the fovea there are almost exclusively cones, and they are at their highest density.
The ratio of ganglion cells : photoreceptors is about 2 :1 here, the highest in the eye. In addition, at the fovea all of the other cell types squeeze out of the way to allow the most light to hit the cones. This makes the fovea visible microscopically. The blood vessels also skirt a wide margin around the fovea. The area in and around the fovea has a pale yellow pigmentation that is visible through an ophthalmoscope, and is called the ____

Back 89

macula.

Front 90

- The cornea is continuous with the ____, which in turn is continuous with the dura.
- The ____, a highly vascular, highly pigmented layer between the sclera and the retina, is continuous with the ciliary body and the iris. Do not confuse it with the pigment epithelium.
- The _____ is a single cell layer thick, and comes from the outer layer of the original optic cup (a classic embryological "pushed-in ball"). In the mature retina it is pushed directly up next to the neural retina, which came from the inner layer of the optic cup. They are not fused together, however, and can separate along the old plane - a "separated" or "detached" retina.

Back 90

sclera

choroid

pigment epithelium

Front 91

Of the 2 types of photoreceptors, the ___ are more sensitive to low-intensity light and therefore are more important than the cones for night vision.

Back 91

rods

They adapt to darkness after the cones, which are primarily involved in color vision.

Front 92

Rods are not present in the

Back 92

fovea.

Front 93

Light converts 11-cis retinal to _____, which is converted to intermediates such as metarhodopsin II.  Metarhodopsin II activates a stimulatory G protein (_____) which activates a phosphodiesterase.  Phosphodiesterase breaks down cyclic guanosin monophosphate (cGMP) so intracellular cGMP levels decrease, causing closure of Na+ channels in the photoreceptor cell membrane and ______


Hyperpolarization inhibits release of neurotransmitter.  If the neurotransmitter is excitatory, then the bipolar cell will be hyperpolarized (inhibited).  If the neurotransmitter is inhibitory, then the bipolar cell will be depolarized (excited).

Back 93

all-trans retinal

transducin

hyperpolarization.

Front 94

Simple and complex cells (both of the visual cortex) respond to moving bars or edges with the correct _____

Back 94

orientation.