Mammalian sense organs

What the syllabus asks of you

• Describe sense organs as groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals
• Identify, on a diagram, the structures of the eye, limited to: cornea, iris, pupil, lens, ciliary muscles, suspensory ligaments, retina, fovea, optic nerve and blind spot
• Describe the function of each part of the eye, limited to: (a) cornea – refracts light (b) iris – controls how much light enters the pupil (c) lens – focuses light onto the retina (d) ciliary muscles and suspensory ligaments – control the shape of the lens (e) retina – contains light receptors, some sensitive to light of different colours (f) fovea – contains the greatest density of light receptors (g) optic nerve – carries impulses to the brain
• Explain the pupil reflex in terms of light intensity and antagonistic action of circular and radial muscles in the iris
• Explain accommodation to view near and distant objects in terms of the contraction and relaxation of the ciliary muscles, tension in the suspensory ligaments, shape of the lens and refraction of light