Visual system

Question 1

5. What happens at the LGN?

Answer 1

Information is pre-processed before going to the primary visual cortex

Question 2

7. What pathway deals with object identity?

Answer 2

Ventral pathway – (sometimes called the what pathway

Question 3

8. What does the dorsal pathway do?

Answer 3

Detects object speed (spatial location)

Question 4

11. What is the function of Muller cells and why are they needed?

Answer 4

They focus the light on to the photoreceptor cells because light has to travel through a lot of tissue before reaching the rod and cone cells

Question 5

12. How many layers of neurons are there in the retina?

Answer 5

3

Question 6

13. How many layers of synapses are there?

Answer 6

2

Question 7

14. What are the 3 types of feedforward (activation) neurons?

Answer 7

Photoreceptopr cells, ganglion cells, bipolar cells

Question 8

15. What are the 2 kinds of feedback (inhibitory) neurons?

Answer 8

Amacrine cells and horizontal cells

Question 9

16. What are the 2 layers of synapses?

Answer 9

Inner plexiform layer and outer plexiform layer

Question 10

18. What happens in the outer segment of the photoreceptor cell?

Answer 10

Phototransduction

Question 11

19. How do photoreceptors respond to light flashes? (depolarisation or hyperpolarisation

Answer 11

Hyperpolarisation

Question 12

20. What does cyclic GMP do?

Answer 12

Activates channels on the photoreceptor membrane

Question 13

Signalling pathway for opsins?

Answer 13

Opsins change conformation ==> ACtivates GPCR ==> Activate PDE ==> Cyclic GMP down regulated ==> Channels close ==> hyperpolarisation ==> Down reg of glutamate ==> Horizontal and bipolar cells receive less activation

Question 14

Sign inverting synapse?

Answer 14

When photoreceptor activated - less glutamate released
Glutamate prevents channel opening and depolarisation
On cells express metabotropic (inhibitory) glutamate receptors
Off cells express inotropic (excitatory) glutamate receptors

Question 15

25. What is centre surround organisation of the receptive field?

Answer 15

Illumination of the centre and the surround leads to responses of opposite polarities

Question 16

1. What are the 2 major classes of ganglion cells?

Answer 16

Parvocellular and magnocellular

Question 17

30. What are their types of responses?

Answer 17

Parvocellular – sustained

Magnocellular – transient

Question 18

Are OFF bipolar cells hyperpolarised or depolarised by light?

Answer 18

hyperpolarised

Question 19

Are ON bipolar cells hyperpolarised or depolarised by light?

Answer 19

Depolarised (reversing hyperpolarisation of photoreceptor cell)

Question 20

What does an OFF center RGC receive input from? (which type of bipolar cell?

Answer 20

An OFF bipolar cell

Question 21

What happens if light is shone on the center of an ON center cell?

Answer 21

Photoreceptor hyperpolarised but bipolar cell is maximally excited

Question 22

What happens if light is only shone on surround of ON center cell?

Answer 22

Surround releases less NT and horizontal cells are not excited
horizontal cells inhibitory signals are low
Center cone doesn’t depolarise as much and bipolar cell is not as excited