ANAT 321 Lecture Notes - Lecture 15: Transducin, Ganglion Cell, Retina Horizontal Cell
12 Oct 2016
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Summarize: light is transformed into a biological signal by a g-protein cascade mechanism: rhodopsin (gpcr) --> transducin (g-protein, transducin is an intracellular protein. Inside the rod, there is a high concentration of cgmp in the dark: depolarized, degrading of cgmp, ion channels close, cell hyperpolarizes. Activation of a single rhodopsin molecule initiates this amplification cascade, and can actually. It can change in any amount in between these extremes. Bipolar cells connect photoreceptors to retinal ganglion cells: neurotransmitters are released in the dark by the cones (when they are depolarized) The neurotransmitter is glutamate (usually excitatory: at the synapse between the cone and the bipolar cell, the glutamate is inhibitory. The cone inhibits the bipolar cell - it is hyperpolarized. The bipolar cell is similar to the cone in that the membrane potential changes are graded - changes continuously over a range: these cells are hyperpolarized in the dark.
