Chapter 5 pt.2

Question 1

What happens to Light after it hits the Retina

Answer 1

It passes through 5 layers of cells to get to the photosensitive cells/photoreceptors, where it it converted to chemical energy

Question 2

what are the two types of photosensitive cells and what do they do

Answer 2

Rods- most responsive to low levels of light (animals have a lot which is why they cans see in the dark)

Cones - most responsive to bright lights and communicating information about colour

both covert the energy into a chemical message

Question 3

What happens after the chemical reaction/change caused by the photosensitive cells

Answer 3

They send the message to the adjacent neuron, then sent to the brain

Question 4

How many photosensitive cells does the retina contain

Answer 4

126 million

Question 5

When is it easier to see in the dark

Answer 5

when the light is on the side of the fovea (cluster of cones)

Question 6

What is visual acuity

Answer 6

when cones transmit information about fine detail

Question 7

What is dark adaptation

Answer 7

when rods and cones adapt to changes in light

Question 8

Whats the first stage of dark adaptation

Answer 8

the cones rapidly respond to the change of light and after 8 minutes they aren’t sensitive to it anymore

Question 9

what’s the second stage of dark adaptation

Answer 9

the rods increase their sensitivity for an additional 20 mins

Question 10

Why do we first see vision upside-down

Answer 10

we see up side down but the lens inverts it

Question 11

What are Bipolar Cells

Answer 11

They add together the firing of the photoreceptive cells and send different kinds of messages to the Ganglion cell

Question 12

What are Diffuse Bipolar Cells

Answer 12

They receive signals from the rods (about 50 rods) and send it to the large ganglion cells

Question 13

What are midget bipolar cells

Answer 13

receive signals from a single cone and send it to a single/small ganglion cell

Question 14

What are characteristics about Small Ganglion Cells (Parvo cells)

Answer 14

• receive information from the midget bipolar cells
• make up 70percent go Ganglion cells
• send signals to the brain about colour and detail

Question 15

What are characteristics about Lange Ganglion cells (mango cells)

Answer 15

• found in the periphery
• receive signals from diffuse bipolar cells
• send information about motion in the periphery

Question 16

What happens when small point of light falls in the centre of the eye

Answer 16

the centre cell increase their firing rate and the centre-off cells (on the edge) decrease their rate of firing

Question 17

what happens when a small portion of light hits the peripheral

Answer 17

the centre will decrease its firing rate and the center off cells will increase its firing rate

Question 18

What happens when the entire receptive field is illuminated

Answer 18

both cells fire off at the same rate

Question 19

What happens when the message finally leaves the eye

Answer 19

it enters the brain through the optic nerve which is made up of axons from the P and M cells

Question 20

Why do we have a blindspot in our vision

Answer 20

because there is a gap/spot in the retina with no photoreceptor axons (the ganglion)

Question 21

What is the Optic Chasim

Answer 21

An “X” shaped structure where the optic nerves from each eye cross before the message is sent to the thalamus

Question 22

How does the information from both eyes travel

Answer 22

information from the right side of both eyes are sent to the left hemisphere and information from the left side of both eyes are sent to the right hemisphere

Question 23

What is the lateral geniculate nucleus

Answer 23

The 6 layered portion of the thalamus that processes and organizes visual information

-each layer deals with specific types of information

Question 24

What is the Visual Striate Cortex

Answer 24

its located in the optical lobe and is where features of the visual lobe are identified

Question 25

What is Retinotopic organization

Answer 25

when the spatial organization of the retinal image is maintained through a visual pathway

Question 26

What are feature detectors

Answer 26

specialized cells in the visual striate that respond actively to specific stimuli