Sense OrgansCambridge IGCSE Biology: Flashcards

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What is a sense organ?

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What is a sense organ?: A group of receptor cells that responds to a specific stimulus, e.g. light, sound, touch, temperature, chemicals.
What is the function of the cornea?: It refracts (bends) light as it enters the eye.
What is the function of the iris?: It controls how much light enters the eye through the pupil.
What is the function of the lens?: It focuses light onto the retina.
What is the function of the retina?: It contains light receptors, some sensitive to different colours of light.
What is the function of the optic nerve?: It carries impulses from the retina to the brain.
What happens to the pupil in bright light, and which muscles cause it?: The pupil constricts (gets smaller); circular muscles in the iris contract.
What happens to the pupil in dim light, and which muscles cause it?: The pupil dilates (gets bigger); radial muscles in the iris contract.
What is accommodation?: The process by which the eye changes the shape of the lens to focus on objects at different distances.
Describe the changes in the eye when focusing on a near object.: Ciliary muscles contract, suspensory ligaments slacken, and the lens becomes fatter.
Describe the changes in the eye when focusing on a distant object.: Ciliary muscles relax, suspensory ligaments become tight, and the lens becomes thinner.
What is the difference between rods and cones?: Rods are sensitive to dim light for night vision; cones are responsible for colour vision and there are three types, each sensitive to a different colour.
What is the fovea, and why is it important?: A region of the retina with a high concentration of cones, giving the sharpest, most detailed colour vision.