Visual System Physiology

Question 1

Photoreceptor cells are connected to?

Answer 1

Bipolar cells

Question 2

Bipolar cells are connected to?

Answer 2

Ganglion cells

Question 3

What cell’s axons form the optic nerve?

Answer 3

Ganglion cells

Question 4

Where does the amount of rods peak?

Answer 4

20 degrees off center

Question 5

Where does the amount of cones peak?

Answer 5

At the center - fovea

Question 6

Cones are used for?

Answer 6

Color detection and visual acuity

Question 7

Rods are used for?

Answer 7

Light detection and have a high sensitivity

Question 8

Darkness does what to the photoreceptor cells?

Answer 8

Depolarizes

Question 9

If a photoreceptor is depolarized, what will it release to the bipolar cell?

Answer 9

LOTS of glutamate

Question 10

If LOTS of glutamate is released to a bipolar cell, what receptor will it bind?

Answer 10

mGLUR6

Question 11

What is the action of mGLUR6?

Answer 11

It closes cGMP-gated sodium channels = bipolar cell is inhibited!

Question 12

Light does what to the photoreceptor cells?

Answer 12

Hyperpolarizes

Question 13

If a photoreceptor is hyperpolarized, what will it release to the bipolar cell?

Answer 13

LOW amounts of glutamate

Question 14

If LOW amounts of glutamate are released to a bipolar cell, what happens?

Answer 14

The bipolar cell will spontaneously depolarize

Question 15

If a bipolar cell depolarizes, it will release ____ to the ganglion cell and _____ it

Answer 15

Glutamate

Depolarize

Question 16

What neurotransmitter do ganglion cells release?

Answer 16

Glutamate

Question 17

What type of glutamate receptor does the ganglion cell have?

Answer 17

Normal - NMDA or non-NMDA that work to excite the cell with glutamate

Question 18

What is the rate of glutamate release from photoreceptor cells?

Answer 18

Constant - only the amounts are changeable

Question 19

What are some direct targets of the retina?

Answer 19

LGN
Superior colliculus
Pretectum
Hypothalamus
Accessory optic nuclei

Question 20

Converge eyes to a point, controls focus, detects movement, maps position of objects around you

Answer 20

Lateral Geniculate Nucleus

Question 21

What are the physiologic areas in the visual cortex?

Answer 21

V1, V2, V3A, V4, MT/V5

Question 22

V1’s job?

Answer 22

Identify edges and contours of objects

Question 23

V2’s job?

Answer 23

Depth perception

Question 24

V3A’s job?

Answer 24

Identify motion; as in did it happen or not? - no processing

Question 25

V4's job?

Answer 25

Complete processing of color inputs

Question 26

MT/V5's job?

Answer 26

Tracks motion across a scene in terms of directionality and context of background

Question 27

Lesion of V4 can result in?

Answer 27

Achromatopsia

Question 28

Achromatopsia

Answer 28

Problems seeing color especially if lesion is bilateral

Question 29

What is the organization of things in the 6 layers of the visual cortex?

Answer 29

Ocular dominance columns, orientation columns and blobs

Question 30

What do ocular dominance columns respond to?

Answer 30

Input from one eye or the other

Question 31

Ocular dominance columns and orientation columns run _______ to each other

Answer 31

Perpendicular

Question 32

Neurons in an orientation column are excited by?

Answer 32

Visual line stimuli of varying angles depending on the column

Question 33

Neurons in blobs are sensitive to?

Answer 33

Color

Question 34

What shape are blobs?

Answer 34

Cylindrical that drill down into the cortex

Question 35

Do ocular dominance columns, orientation columns and blobs span all layers of the visual cortex?

Answer 35

YES

Question 36

What are MG cells?

Answer 36

Melanopsin Ganglion cells

Question 37

What is special about MG cells?

Answer 37

They can directly sense light, specifically blue light

Question 38

What do MG cells help to regulate?

Answer 38

Circadian rhythm

Question 39

Where do MG cells project?

Answer 39

Hypothalamic suprachiasmatic nucleus in the pineal gland that releases melatonin

Question 40

Non-image-forming light responsive system?

Answer 40

Melanopsin ganglion cells

Question 41

Patient's who are blind due to photoreceptor cell loss still have what?

Answer 41

MG cells, and thus are responsive to some blue light and have a circadian rhythm

Question 42

Where is the lesion if a patient is blind and lacks a circadian rhythm?

Answer 42

CN2 --affects all cells in the retina

Question 43

Why do older people experience sleep issues?

Answer 43

Their lens becomes more yellowish and decreases blue light transmission throughout the day

Question 44

Blue light exposure before sleep can _____ sleep

Answer 44

Disrupt

Question 45

Can treat seasonal depression, increase alertness and stimulate cognition

Answer 45

Blue light

Question 46

This pathway is the primary path for associating vision with movement

Answer 46

Dorsal pathway

Question 47

Dorsal pathway completes?

Answer 47

Motor acts based on visual imput

Question 48

What is the dorsal pathway steps?

Answer 48

V1 - V2/V3 - MT/V5 - Parietal lobe

Question 49

This pathway is the pathway that interprets images

Answer 49

Ventral pathway

Question 50

Ventral pathway recognizes?

Answer 50

Shapes, forms, faces

Question 51

What is the ventral pathway steps?

Answer 51

V1 - V2 - V4 - inferior temporal lobe

Question 52

What areas in the temporal lobe have their own area, thus if one is damaged the others may not be?

Answer 52

Copying objects, naming objects and facial recognition