Photoreceptor cell cell depends upon only the number of photons absorbed. The different responses of the three types of cone cells are determined by the likelihoods that their respective photoreceptor proteins will absorb photons of different wavelengths. So, for example, an L cone cell contains a photoreceptor protein that more readily absorbs long wavelengths of light (i.e., more "red"). Light of a shorter wavelength can also produce the same response, but it must be much brighter to do so. The human retina contains about 120 million rod cells, and 6 million cone cells. The number and ratio of rods to cones varies
Retina horizontal cell However, when recordings are made from parts of the cone that are distant from the cone terminals that synapse onto bipolar cells, center-surround antagonism seems to be less reliable in cones than in bipolar cells. As the invaginating synapses from horizontal cells are made onto cone terminals, the center-surround antagonism of cones is thought to be more reliably present in cone terminals. Retina horizontal cell Horizontal cells are the laterally interconnecting neurons having cell bodies in the inner nuclear layer of the retina of vertebrate eyes. They help integrate and regulate the input from multiple photoreceptor cells. Among their functions,