Cells of the Retina

Question 1

Discuss bipolar cells

Answer 1

1. Receive input from photoreceptors

2. Sends response to ganglion cells

Question 2

What are the 3 types of bipolar cells?

Answer 2

1. Rod bipolar: Depolarize and increase activity in response to stimuli brighter than background. Vice versa
2. ‘On’ cone bipolar: same as rod bipolar
3. ‘Off’ cone bipolar: reverse of rod bipolar

Question 3

What happens to rods and cones during illumination?

Answer 3

When there is an increase in illumination, both rod and cone photoreceptors hyperpolarize, resulting in a decrease in transmitter release. Due to differences in their glutamate receptors, Rod and ON cone Bipolar cells depolarize in response to the reduced levels of transmitter, whereas OFF cone Bipolar cells hyperpolarize

Question 4

What happens to rods and cones during a decrease in illumination?

Answer 4

A decrease in illumination results in the opposite response: Photoreceptors increase their transmitter output, ON cone Bipolar, Rod Bipolar, and ON Ganglion cell activity decreases, while OFF cone Bipolar and OFF Ganglion cell activity increases.

Question 5

What is a receptive field?

Answer 5

Amount of visual space which, when a visual stimulus is present, results in a change in the firing rate of the neuron – may be increased or decreased activity.

Question 6

Describe the receptive field of photoreceptors

Answer 6

Unifom; same response regardless of where the stimulus is in the field.

Question 7

Describe the receptive field of Bipolar and Ganglion cells.

Answer 7

Non-uniform; This information concerning local intensity differences is important for the detection of edges and borders, which are defined by variations in the levels of reflected light.

Question 8

What is the role of Amacrine cells?

Answer 8

Temporal modulation of ganglion cell responses

Question 9

What are the 2 types of Ganglion cells?

Answer 9

1. Midget cells

2. Parasol cells