Opsin-containing disks lie at the end of the cell adjacent to the retinal pigment epithelium, which in turn is attached to the inside of the eye.

The stacked-disc structure of the detector portion of the cell allows for very high efficiency.

Glutamate can depolarize some neurons and hyperpolarize others, allowing photoreceptors to interact in an antagonistic manner.

The retinal exists in the 11-cis-retinal form when in the dark, and stimulation by light causes its structure to change to all-trans-retinal.

As a result, the alpha subunit is now free to bind to the cGMP phosphodiesterase (an effector protein).

The entire process by which light initiates a sensory response is called visual phototransduction.

Activation of a single unit of rhodopsin, the photosensitive pigment in rods, can lead to a large reaction in the cell because the signal is amplified.

This opens the cGMP sensitive channels and causes a depolarization of the plasma membrane.

[10] When the rods are exposed to a high concentration of photons for a prolonged period, they become desensitized (adapted) to the environment.

Since rods require less light to function than cones, they are the primary source of visual information at night (scotopic vision).

Additionally, multiple rod cells converge on a single interneuron, collecting and amplifying the signals.

Rod cells also respond more slowly to light than cones and the stimuli they receive are added over roughly 100 milliseconds.