Final answer:
Photoreceptors like rods and cones convert light into a neural signal by utilizing photopigments such as rhodopsin. Light triggers a shape change in the retinal molecule causing hyperpolarization and altered neurotransmitter release. This process initiates a visual signal that is sent to the brain.
Step-by-step explanation:
Photoreceptors, such as rods and cones in the retina, contain photopigments like rhodopsin which are crucial in the transduction of light into neural signals. Upon absorption of light, the retinal molecule within the photopigment undergoes a shape change, transitioning from a bent (cis) form to a linear (trans) configuration. This change activates the rhodopsin, leading to a cascade of events that hyperpolarizes the photoreceptor cells by closing Na+ channels. This hyperpolarization causes the photoreceptors to release less neurotransmitter onto the bipolar cells, which results in the activation of the bipolar cells.
This process contrasts with other sensory neurons which typically depolarize upon stimulus. Instead, the hyperpolarization triggers a decrease in the baseline tonic activity of the photoreceptor, allowing a signal to be sent to secondary neurons like bipolar and ganglion cells. This signaling is essential for the perception of light and forms the basis for visual information that is transmitted to the brain. After the retinal isomerization, various enzymatic changes are necessary to revert retinal to its original shape, allowing the photoreceptor to reset and respond to new light stimuli.