Final answer:
Sustained responses similar to parvocellular ganglion cells occur in tonic photoreceptors in the retina and the autonomic nervous system's control of the pupillary light reflex. These mechanisms ensure a steady visual experience by making continuous adjustments to lighting conditions.
Step-by-step explanation:
Cells and receptors in different systems which have a sustained response like parvocellular ganglion cells include tonic photoreceptors in the retina and cells involved in the pupillary light reflex. Tonic photoreceptors are always slightly active, adapting to baseline activity in the absence of stimuli, whereas the pupillary light reflex involves the sympathetic and parasympathetic systems controlling pupillary size in response to light levels, ensuring homeostatic control.
The pupillary light reflex is a prime example of sustained response, which adjusts the amount of light entering the retina through pupil dilation or constriction mediated by the autonomic nervous system. Like the parvocellular ganglion cells, these reflex mechanisms maintain consistent activity levels to ensure visual acuity and contrast in varied lighting conditions.