BS - Retina Part 1 - Week 3

Question 1

Name the two types of glial cells, and give examples for each (4 total). Describe which part of the nervous system it is involved in, if applicable.

Answer 1

Microglia
-mononuclear phagocytes/macrophage
Macroglia
-Schwann cells - PNS
-Oligodendrocytes - CNS
-Astrocytes - CNS

Question 2

Define soma.

Answer 2

Neural cell body.

Question 3

Compare electrical synapse vs chemical synapse.

Answer 3

Chemical - gap junction between synapses uses neurotransmitters to continue the signal.
Electrical - no neurotransmitters used, gap junction is small enough to allow ionic transfer of the signal.

Question 4

Where do chemiscal transmitters typically originate from?

Answer 4

TCA cycle.

Question 5

What cells are responsible for myelination?

Answer 5

Schwann cells - PNS

Oligodentrocytes - CNS

Question 6

What matter do Schwann cells myelinate?

Answer 6

White matter

Question 7

What matter do Schwann cells surround, and why?

Answer 7

Grey matter cell bodies, for support.

Question 8

What is the most numerous glial cell type in the CNS?

Answer 8

Astrocytes

Question 9

Name 2 functions of astrocytes, and what they resemble.

Answer 9

Star shaped cells.
-Play a role in forming the blood-brain barrier.
Regulate potassium concentration in the ECM between neurons.

Question 10

Define the following:
Optic Disk
Optic Cup
Neuroretinal Rim

Answer 10

Optic cup is a small white circle within the larger optic disk.
The neuroretinal rim is the donut-shaped rim around the optic cup to the border of the optic disk.

Question 11

What is the anterior border of the retina?

Answer 11

Ora serrata.

Question 12

Does the fovea (also macula lutea) have any vascularisation?

Answer 12

No, it is avascular.

Question 13

What type of cell is present at the fovea in high density, cones or rods?

Answer 13

High cone density, no rods are present.

Question 14

Where does the fovea receive its blood supply?

Answer 14

The underlying choriocapillaris.

Question 15

Does the RPE have any neurological function?

Answer 15

No, its only purpose is to absorb light and support photoreceptor cells.

Question 16

What shape do RPE cells have, and what is it continuous with?

Answer 16

They are hexagonal, and continuous with the posterior surface of the iris.

Question 17

What type of vision are rod cells used for, what level of acuity do they provide, and do they have colour?

Answer 17

They have high sensitivity, used for scotopic vision, provide low acuity, and are achromatic.

Question 18

What type of vision are cone cells used for, what level of acuity do they provide, and do they have colour?

Answer 18

They have low sensitivity, used for photopic vision, provide high acuity, and are chromatic.

Question 19

What can be found at the outer plexiform layer?

Answer 19

Each cone/rod contacts several hundred processes of bipolar and horizontal cells.

Question 20

What can be found at the inner nuclear layer? Name 4 structures.

Answer 20

Somas of:

• Horizontal cells
• Bipolar cells
• Muller cells
• Amacrine cells

Question 21

What are the two retinal pathways, and what cells are involved in both?

Answer 21

Vertical
-Photoreceptors
-Bipolar cells
Horizontal
-Horizontal cells
-Amacrine cells

Question 22

What are the two main physiological types of bipolar cells, and how can they be differentiated (hint, one of the layers)?

Answer 22

Off bipolar cells, responding to darkness
On bipolar cells, responding to light
Off cells have their output synapses at sublamina a of the the inner plexiform layer, the outer half.
On cells have their output synapses at sublamina b of the inner plexiform layer, the inner half.

Question 23

Where do bipolar cells form their output synapses, and what neurotransmitter is used at the presynaptic terminal?

Answer 23

Inner plexiform layer, using glutamate.

Question 24

Where are the somas of ganglion cells found?

Answer 24

In the ganglion cell layer.

Question 25

Where do the dendrites of ganglion cells receive their input from?

Answer 25

Inner plexiform layer.

Question 26

Where are the somas of horizontal cells located?

Answer 26

Inner nuclear layer.

Question 27

What two cells are linked by horizontal cells, and what pathway does this form? What kind of feedback does it provide to them, and for what purpose?

Answer 27

Link photoreceptor cells and bipolar cells, in the horizontal pathway.
Provides inhibitory feedback, allowing the eyes to adjust for either bright or dim conditions.

Question 28

What are the three types of horizontal cells? How do they differ?

Answer 28

H1, H2, and H3. Differ by their connections to S cones.

Question 29

What are amacrine cells, where are their processes and somas found, and what kind of feedback does it give? What is its role?

Answer 29

They are interneurons in the horizontal pathway.
Their somas are in the inner nuclear layer.
Processes are in the inner plexiform layer.
Provides inhibitory feedback, playing a modulatory role.

Question 30

What neurotransmitter do amacrine cells use?

Answer 30

GABA or glycine.

Question 31

Whith which cells do amacrine cells have postsynaptic connections with?

Answer 31

Bipolar, amacrine, or ganglion cell processes.

Question 32

Where are astrocytes located?

Answer 32

Ganglion cell layer.

Question 33

Where are muller cell bodies and processes located?

Answer 33

Somas - middle of the inner nuclear layer

Processes extend vertically through the retina, filling up space between cells.

Question 34

What 5 functions do muller cells have?

Answer 34

• Take up excess neurotransmitter
• Transport nutrients to neurons
• Take up excess potassium and release it into the vitreous
• Surrounds retinal blood cells
• Immune surveillance

Question 35

What cells form the inner and outer limiting membrane?

Answer 35

The end processes of muller cells, which extend from the outer to inner limiting membranes.

Question 36

Where are the outer and inner limiting membranes?

Answer 36

Outer - found at the pase of photoreceptors, above their somas.
Inner - Deep to the ganglion cell layer, overlying the neural fibre layer.