Purely depolorizing cells in optic pathway ?
Ans. is 'a' i.e., Amacrine cells The responses of the rods, cones and horizontal cells are hyperpolarizing. Bipolar cells may show either hyperpolarization or depolarization. All these cells develop only graded local potentials, i.e., nonpropagated, decremental, does not follow all or none law. These cells do not develop action potential. The only cell which develops propagated action potential is ganglion cells and the response is always depolarizing. Otherwise, they remains in inactive state. Amacrine cells produce depolarizing potential and spikes. Rods and cones release glutamate at their synapses with the bipolar cells. Amacrine cells secrete at least eight types of transmitter substances, including GABA, glycine, dopamine, acetylcholine and indolamine, all of which normally function as inhibitory neurotransmitters. The transmitters of the bipolar cells and horizontal cells are unclear.
Amacrine cells
Rods & cones
Bipolar cells
Horizontal cells