Eye + Retina (Continued)👁
Bipolar Cells
Horizontal Cells
Ganglion Cells
ON bipolar cells✅
OFF bipolar cells❎
Depolarize in response to light ON💡
Depolarize in response to light OFF🌑
G-protein coupled glutamate receptors == mGluR6
Glutamate binds in dark
Hyperpolarization
Makes voltage more (+)
AMPA glutamate receptors
Glutamate binds in dark
Depolarization
Makes voltage more (-)
System of 2 different types of bipolar cells
Gives brain stronger sense🧠
Inhibitory cells releasing GABA
Function
Connect photoreceptors to enhance contrast detection
Light vs dark contrast
If ON bipolar cells depolarize✅
ON ganglion✅
⚡️Action potential firing rate increases⬆️
If OFF bipolar cells depolarize✅
OFF ganglion❎
⚡️Action potential firing rate increases⬆️
Synapse == AMPA glutamate receptors
Synapse == AMPA glutamate receptors
Antagonistic Center-Surround Receptive Fields🎯
Types
P-Type
M-Type
Good at detecting details
Ex. object shape🎁
Good at detecting motion🚙
Magno == large🐘
Wide network of dendrites
Large receptive fields
Parvo == small🐁
Smaller dendritic network
Small receptive fields
ON center
Sudden increase action potential firing rate, but then decreases quickly
ON center
Sudden increase in action potential firing rate, but then decreases slowly (sustained)
Discovered by Stephen Kuffler in 1953🧑🔬
ON ganglion cells✅
🌕"likes" light in center + dark in surround🌑
OFF ganglion cells❎
🌑"likes" dark in center + light in surround🌕
🌑Dark in center + light in surround🌕
Hyperpolarizes cells in surround
Horizontal cells stop releasing GABA
🌑Both center + surround == dark🌑
Surround cells hyperpolarizes + center cells depolarize
🌕Both center + surround == light🌕
Surround cells depolarizes + center cells hyperpolarize
🌕Light in center + dark in surround🌑
Hyperpolarizes cells in center
Function
Detect dark objects in lighter background
Function
Detect light objects in darker background
Control responses of "center" photoreceptor
Indirectly produce bipolar cell receptive field surround effect
Horizontal cells further hyperpolarize