How do Rods have high visual sensitivity

DIM LIGHT stimulates the rods , light absorbed by pigments ACH RELEASE ach released from each rod receptor diffuses across post sypatic membrane as multiple rods are connected to one bipolar neurone , ach builds up so more NA+ gated channels open so NA+ diffuse in causing AS SPATIAL SUMMATION so THRESHOLD TO BE PASSED. Action potentials move along the bipolar neurone to the optic nerve , causing high visual sensitivity BUT CONES IT IS THE OPPOSITE AS CONNECTED TO THEIR OWN BP SO THRESHOLD NOT PASSED