CENTRAL VISUAL PATHWAY

Question 1

The eye is a fluid-filled sphere enclosed by 3 layers of tissue:

Answer 1

Sclera: Outermost layer
Choroid: Intermediate layer
Retina: Innermost layer

Question 2

Which fluid compartement is in the anterior chamber and is a watery liquid

Answer 2

aqueous humor

Question 3

describe vitrous humor and function

Answer 3

a thick gelatinous substance. It fills the space between the back of the lens and the retina. It maintains the shape of the eye and supplies nutriments to surrounding structures

Question 4

what is the sclera and what does it become in front of the eyes

Answer 4

white fibrous tissue forming the outermost layer of the eye. At the front of the eye, it becomes the Cornea

Question 5

what is the cornea

Answer 5

a transparent tissue that separates and protects the eye from the external environment and allows light rays into the eye.

Question 6

what is the coroid

Answer 6

capillary bed that nourishes the retinal cells

Question 7

what is the cilary body

Answer 7

a ring of tissue that encircles the lens and consists of a muscular and vascular part

Question 8

what is the ciliary muscle

Answer 8

controls the shape of the lens. Connected to the lens by the Zonule fibers.

Question 9

what is the ciliary process

Answer 9

produces the aqueous humor in the anterior chamber

Question 10

what is the iris

Answer 10

coloured portion of the eye seen through the cornea, contains 2 sets of muscles that contract and to adjust the size of the pupil

Question 11

what is the lens

Answer 11

Lens refracts (bends) light rays coming into the eye and generates a focused image on the surface of the retina.

Question 12

what is the accomodation of the lens

Answer 12

dynamic changes in the refractive power of the lens to form a shape image on the retina. These changes are made by the contraction of the Ciliary muscle.

Question 13

what happen with lens with distant vision and near vision

Answer 13

Distant vision: lens becomes thin and flat. Less refractive power.
Near vision: lens becomes thick and round. Most refractive power

Question 14

what is emmetropia

Answer 14

: In the normal eye, the lens has a right accommodation level, the image is focused right on the retina.

Question 15

what is myopia

Answer 15

the lens does not accommodate enough, the image is focused in front of the retina. Hard to see distant objects. Corrected by convex (converging) eye glasses.

Question 16

what is hyperopia

Answer 16

the lens over accommodate, the image is focused beyond the retina. Hard to see a nearby objects. Corrected by concave (diverging) eye glasses

Question 17

what is the retina

Answer 17

the innermost layer of the eye.
The retina is considered a part of the Nervous System. It contains neurons that are sensitive to light and convert visual information to electrical signal and transmit it the brain

Question 18

Photosensitive (photoreceptor) neurons:

Answer 18

rods and cones

Question 19

which one btw rods and cones make the color vison

Answer 19

cone

Question 20

which one create bright light and which one night vision

Answer 20

bright: cone
night: rods

Question 21

which one produce periphery vision and which one produce center vision

Answer 21

rods: peri
cone: center

Question 22

which produce low resolution and which one high resolution accuracy

Answer 22

cones: high
rodds: low

Question 23

what are the 5 classes of neurons of retina

Answer 23

photosensitive
bipolar
ganglion
horizontal cell
amacrine cell

Question 24

which neuron regulate the activity of photosensitive

Answer 24

horizontal cell

Question 25

which cell make the Lateral communication between neurons

Answer 25

amacrine cells

Question 26

what are the 2 classes of ganglion cells

Answer 26

on center cell
off-center cell

Question 27

role of on-center cells

Answer 27

active to light spot in center and silent to dark spot in center.

Question 28

role of off-center cells

Answer 28

silent to light spot in center and active to dark spot in center.

Question 29

which cells also have on-center and off-center cells

Answer 29

bipolar cells

Question 30

The activity of the On-center/Off-center ganglion cells is controlled by

Answer 30

multiple interactions between the photosensitive cells (cone/rod), bipolar cells and at horizontal cells.

Question 31

how is the image convert on the retina

Answer 31

the image is inverted top to bottom and reversed right to left.

Question 32

what is the visual field

Answer 32

part of word seen by the eye. It can be divided to 2 hemi-fields:

Question 33

right visual hemi-field is seen by

Answer 33

the right nasal retina & left temporal retina.

Question 34

left visual hemi-field is seen by

Answer 34

): seen by the left nasal retina & right temporal retina.

Question 35

qhat is the binocular visual field

Answer 35

Visual fields of both eyes overlap in the central portion of the visual field =

Question 36

60% of the optic nerve fibres crosse at the

Answer 36

optic chiasma to the opposite side of the brain

Question 37

40 % of fiber goes where

Answer 37

stay on the same side (ipsilateral) of the brain.

Question 38

Fibres from the nasal retina project to the

Answer 38

contralateral side of the brain (i.e. crosse the optic chiasm).

Question 39

Fibres from the temporal retina project to the

Answer 39

ipsilateral side

Question 40

after the optic chiasma, the optic fiber form what

Answer 40

optic tract

Question 41

The majority of optic fibres terminate in the

Answer 41

Lateral Geniculate Body (LGB) in the thalamus.

Question 42

neuron from LGB form what and terminate where

Answer 42

Neurons from the LGB form the optic radiation and terminate in the striate cortex (occipital cortex).

Question 43

neuron from LGB form what and terminate where

Answer 43

Neurons from the LGB form the optic radiation and terminate in the striate cortex (occipital cortex).

Question 44

role of hypothalamus, pretectum, superior colliculus

Answer 44

Hypothalamus: regulation of circadian rhythms (biological clock).
Pretectum: control of the pupillary light reflex.
Superior colliculus: orienting the movements of head and eyes (see the vestibular system).

Question 45

role of visual cortex

Answer 45

processes the basic of the sensory information sent by the retina (e.g. place back the inverted image to its original position, binocular vision, 3D image, ect)

Question 46

which info have a large representation in th visual cortex

Answer 46

Sensory information from the central region of the retina (macula, fovea) have a large representation in the visual cortex. the central region of the retina sends the large portion of sensory information to the visual cortex.

Question 47

what is the name of the 6 cellules layer in striate cortex

Answer 47

“Cytoarchitecture”;

Question 48

geniculate neuron are mono or bicular

Answer 48

monocular

Question 49

The lateral geniculate nucleus (LGN) receives input

Answer 49

both eye

Question 50

LGN input remain segreated where

Answer 50

in layer 4 of the striate cortex (ocular dominance columns). Here also the neurons are still monocular.

Question 51

in which state the image from both eye are converge onto a single image

Answer 51

Layer 4 neurons send their outputs to other cortical layers; it is at this stage that the images from both eyes converges onto a single image (cyclopean representation of the external world = binocular vision).

Question 52

role of Dorsal pathway (where pathway

Answer 52

projects to the parietal lobe. Responsible of spatial aspect of vision (e.g. analysis of motion, positional relationship between objects…ect).