BS - Retina Part 1 - Week 3 Flashcards
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.
Microglia -mononuclear phagocytes/macrophage Macroglia -Schwann cells - PNS -Oligodendrocytes - CNS -Astrocytes - CNS
Define soma.
Neural cell body.
Compare electrical synapse vs chemical synapse.
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.
Where do chemiscal transmitters typically originate from?
TCA cycle.
What cells are responsible for myelination?
Schwann cells - PNS
Oligodentrocytes - CNS
What matter do Schwann cells myelinate?
White matter
What matter do Schwann cells surround, and why?
Grey matter cell bodies, for support.
What is the most numerous glial cell type in the CNS?
Astrocytes
Name 2 functions of astrocytes, and what they resemble.
Star shaped cells.
-Play a role in forming the blood-brain barrier.
Regulate potassium concentration in the ECM between neurons.
Define the following:
Optic Disk
Optic Cup
Neuroretinal Rim
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.
What is the anterior border of the retina?
Ora serrata.
Does the fovea (also macula lutea) have any vascularisation?
No, it is avascular.
What type of cell is present at the fovea in high density, cones or rods?
High cone density, no rods are present.
Where does the fovea receive its blood supply?
The underlying choriocapillaris.
Does the RPE have any neurological function?
No, its only purpose is to absorb light and support photoreceptor cells.
What shape do RPE cells have, and what is it continuous with?
They are hexagonal, and continuous with the posterior surface of the iris.
What type of vision are rod cells used for, what level of acuity do they provide, and do they have colour?
They have high sensitivity, used for scotopic vision, provide low acuity, and are achromatic.
What type of vision are cone cells used for, what level of acuity do they provide, and do they have colour?
They have low sensitivity, used for photopic vision, provide high acuity, and are chromatic.
What can be found at the outer plexiform layer?
Each cone/rod contacts several hundred processes of bipolar and horizontal cells.
What can be found at the inner nuclear layer? Name 4 structures.
Somas of:
- Horizontal cells
- Bipolar cells
- Muller cells
- Amacrine cells
What are the two retinal pathways, and what cells are involved in both?
Vertical -Photoreceptors -Bipolar cells Horizontal -Horizontal cells -Amacrine cells
What are the two main physiological types of bipolar cells, and how can they be differentiated (hint, one of the layers)?
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.
Where do bipolar cells form their output synapses, and what neurotransmitter is used at the presynaptic terminal?
Inner plexiform layer, using glutamate.
Where are the somas of ganglion cells found?
In the ganglion cell layer.
Where do the dendrites of ganglion cells receive their input from?
Inner plexiform layer.
Where are the somas of horizontal cells located?
Inner nuclear layer.
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?
Link photoreceptor cells and bipolar cells, in the horizontal pathway.
Provides inhibitory feedback, allowing the eyes to adjust for either bright or dim conditions.
What are the three types of horizontal cells? How do they differ?
H1, H2, and H3. Differ by their connections to S cones.
What are amacrine cells, where are their processes and somas found, and what kind of feedback does it give? What is its role?
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.
What neurotransmitter do amacrine cells use?
GABA or glycine.
Whith which cells do amacrine cells have postsynaptic connections with?
Bipolar, amacrine, or ganglion cell processes.
Where are astrocytes located?
Ganglion cell layer.
Where are muller cell bodies and processes located?
Somas - middle of the inner nuclear layer
Processes extend vertically through the retina, filling up space between cells.
What 5 functions do muller cells have?
- Take up excess neurotransmitter
- Transport nutrients to neurons
- Take up excess potassium and release it into the vitreous
- Surrounds retinal blood cells
- Immune surveillance
What cells form the inner and outer limiting membrane?
The end processes of muller cells, which extend from the outer to inner limiting membranes.
Where are the outer and inner limiting membranes?
Outer - found at the pase of photoreceptors, above their somas.
Inner - Deep to the ganglion cell layer, overlying the neural fibre layer.
