receptor potentials of rod cells

in the DARK,  rhodopsin is inactive (CIS) and cGMP is bound to rod cell membranes;  

Na channel is open; rod cell is DEPOLARIZED and releases neurotransmitter GLUTAMATE which excites or inhibits adjacent Bipolar cells = no sensation of light.   

in the LIGHT  rhodopsin changes conformation (TRANS), which activated enzyme TRANSDUCIN;     
                transducin activates a PHOSPHODIESTRASE, converts cyclic-GMP to GMP;              
                GMP closes the Na channels, and HYPERPOLARIZES rod cells (RECEPTOR POTENTIAL);
                hyperpolarized rod cell stops releasing GLUTAMATE, allowing bipolar cells repsond*      











7e fig 49.14 & 8e fig 50.22 effect of light on rod cells