Final answer:
Photoreceptors such as rods and cones in the retina exhibit continuous tonic activity and do not produce action potentials directly. Instead, they adjust their inhibition of bipolar cells in response to light, which in turn affects the activity of retinal ganglion cells that generate action potentials. This system, along with lateral inhibition, contrasts with other sensory systems where receptors trigger action potentials upon stimulation.
Step-by-step explanation:
Photoreceptors in the retina, such as rods and cones, and hair cells in the auditory system are unique compared to other sensory receptors in that they do not normally produce action potentials themselves. Instead, photoreceptors undergo continuous tonic activity, being slightly active even in the absence of light. Upon light exposure, the rods and cones become hyperpolarized, which reduces their inhibition of bipolar cells. The activated bipolar cells then stimulate ganglion cells to send action potentials along the optic nerve, encoding visual signals for the brain. This relationship contrasts with other sensory receptors, which generally become depolarized and directly produce action potentials upon stimuli. In the case of hair cells in the inner ear, their movement induces action potentials in adjacent neurons rather than in the hair cells themselves.
Furthermore, lateral inhibition through horizontal and amacrine cells enhances visual contrast and sharpens the edges in the visual field, a process distinct to the visual system. These adaptations are crucial for the high sensitivity and specificity required for the proper functioning of the visual and auditory systems.