14.2 Sense organs

Sense organs as receptor cells responding to specific stimuli (light, sound, touch, temperature, chemicals) — focused on the human eye. Identify the seven Cambridge parts (cornea, iris, pupil, lens, retina, optic nerve, blind spot) and state each function. Explain the pupil reflex (bright = small, dim = large) as protection of the retina. HL extension: antagonistic action of circular and radial iris muscles, plus accommodation (ciliary muscles + suspensory ligaments + lens shape) to focus on near vs far objects, and the distribution + functions of rods (night vision, periphery), cones (three types for colour vision), and the fovea (cone-packed pit for sharpest vision).