Flashcards in Bipolar Cells (M1) Deck (36):
What channels open once an action potential reaches the axon terminal? 1. Which way do these ions then flow? 2
1. Ca2+ channels
2. flow into cell
At rest, what is the [Ca2+] inside the cell? 1. Outside the cell? 2
1. 0.05 uM
2. 2000uM (2mM)
What are the major differences in photoreceptor neurotransmission compared to normal neurotransmission?
1. PR VGCC'c have low activation threshold (-40mV most open)
2. PR VGCC's inactivate very slowly and remain open longer
Do photoreceptors release more neurotransmitters in the dark or light?
What cells are ribbon synapses found in?
3. retinal bipolar cells
4. cochlear hair cells
5. vestibular organ reeptors
What id the function of ribbon synapse?
shuttle synaptic vesicles to exocytotic sites like a conveyor belt
What is the cone synaptic terminal called?
What are the two ways that horizontal and bipolar cells contact the cone?
2. basal junctions
How many invaginations are usually on one cone? 1. What is the typical arrangement of dendrites in this invagination? 2
2. 2 horizontal cell dendrites and 1 central bipolar dendrite
How many cones does each horizontal cell contact?
What kind of bipolar cells are usually at the flat synapses at the edge of an invagination? 1. Further away from the invagination? 2
1. flat midget bipolar cell (fmb)
2. diffuse flat bipolar cell (fb or db)
What is the rod synaptic terminal called? 1. What kind of connections are on this terminal? 2
1. rod spherule
2. one big invagination
What are the typical arrangements of dendrites in the rod invagination?
horizontal cells lateral and 2 bipolar dendrites centrally
How many rods can each rod bipolar cells receive input from?
What are the two types of bipolar cells (and what is the physiology of each)?
1. OFF bipolar (hyperpolarizes to light)
2. ON bipolar (depolarizes to light)
What kind of midget bipolar cells are usually in invaginating synapses with cones? 1. What kind are usually in flat synapses with cones? 2
1. ON mb
2. OFF mb
Where do OFF bipolars synapse within the inner plexiform layer?
inner nuclear layer
Where do ON bipolars synapse within the inner plexiform layer?
closer to ganglion cell layer
Are OFF bipolar cells sign-conserving or sign-inverting?
Are ON bipolar cells sign-conserving or sign-inverting?
What type of lighting (dark or light) does dumping glutamate on the retina mimick?
dark (depolarize OFF and hyperpolarize ON)
What are the two types of ionotropic glutamate receptors (and do they depolarize or hyperpolarize)?
1. Kainate/AMPA- type (depolarize)
2. NMDA-type (depolarize)
What type of glutamate receptors are present mediate neurotransmission in OFF bipolar cells?
ionotropic Kainate/AMPA receptors
What type of glutamate receptors are present mediate neurotransmission in ON bipolar cells?
metabotropic mGluR6 receptors (G-protein-coupled)
What is the channel that connects mGluR6 to the depolarizing responses seen in ON bipolar cells? 1. What is the G-protein? 2
1. TRPM1 channel
2. G(O) protein
Does the TRPM1 channel open or close after mGluR6 is stimulated by glutamate via a G(O) pathway?
What kind of bipolar cells are associated with rods?
ON bipolar cells only
What are bipolar cells that only synapse with one cone called?
midget bipolar cells
What portion of the eye has a more positive electrical charge? 1. How is this measured? 2
1. front (cornea)
2. electrooculogram (EOG)
Compared to the dark, when the lights are on is the difference in charge from the back of the eye to the front larger or smaller?
larger in light (at least 1.7x larger)
What provides a measure of summed electrical activity in the retina in response to light stimuli?
What is the reason for the a-wave of an ERG? 1. What does this represent? 2
1. reduction in the dark current in PR's stimulated with light
2. functional integrity of photoreceptors
What is the reason for the b-wave of an ERG? 1. What does this represent? 2
1. depolarization of ON bipolar cells or changes in Mullers cells
2. light responses in cells post-synaptic to photoreceptors
What cells seem to drive the ERG?
changes in the outer retina
How can cone contribution be minimized when taking ERG measurements?
use a dimmer light