When a photoreceptor cell is stimulated by light:

Question

Quizplus · Accepted Answer

When a photoreceptor cell is stimulated by light, the photoreceptor hyperpolarizes as sodium ion channels close. This occurs because light causes the breakdown of cis-retinal into trans-retinal, which activates the enzyme rhodopsin kinase, leading to the closure of sodium ion channels and hyperpolarization of the photoreceptor cell. This hyperpolarization then triggers a series of events that ultimately lead to the transmission of visual information to the brain. Sodium ions do not enter the outer segment of the photoreceptor and depolarize it, and transducin and phosphodiesterase (PDE) are actually activated when rhodopsin is phosphorylated by rhodopsin kinase. Opsin and cis-retinal do combine to form rhodopsin, but this occurs before the photoreceptor is stimulated by light.

When a Photoreceptor Cell Is Stimulated by Light