Bipolar Cells (M1) Flashcards
What channels open once an action potential reaches the axon terminal? 1. Which way do these ions then flow? 2
- Ca2+ channels
2. flow into cell
At rest, what is the [Ca2+] inside the cell? 1. Outside the cell? 2
- 0.05 uM
2. 2000uM (2mM)
What are the major differences in photoreceptor neurotransmission compared to normal neurotransmission?
- 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?
dark
What cells are ribbon synapses found in?
- rods
- cones
- retinal bipolar cells
- cochlear hair cells
- 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?
cone pedicle
What are the two ways that horizontal and bipolar cells contact the cone?
- invaginations
2. basal junctions
How many invaginations are usually on one cone? 1. What is the typical arrangement of dendrites in this invagination? 2
- 12-25
2. 2 horizontal cell dendrites and 1 central bipolar dendrite
How many cones does each horizontal cell contact?
7-12
What kind of bipolar cells are usually at the flat synapses at the edge of an invagination? 1. Further away from the invagination? 2
- 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
- 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?
15-50 rods
What are the two types of bipolar cells (and what is the physiology of each)?
- 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
- 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?
sign-conserving
Are ON bipolar cells sign-conserving or sign-inverting?
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)?
- 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)
