Sense Organs
Overview
Your eyes are remarkable light detectors. They bend incoming light, focus it onto a screen of light-sensitive cells, and adjust automatically to bright sunshine or a dim room, all without you noticing. The eye is the best-known example of a sense organ.
In this lesson you will learn what a sense organ is, name the parts of the eye and their jobs, and explain the pupil reflex. For the extended curriculum you will also master accommodation (how the lens changes shape to focus) and the roles of rods and cones in the retina.
Objectives
- Describe sense organs as groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals
- Identify in diagrams and images the structures of the eye, limited to: cornea, iris, pupil, lens, retina, 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 on to the retina (d) retina - contains light receptors, some sensitive to light of different colours (e) optic nerve - carries impulses to the brain
- Explain the pupil reflex, limited to changes in light intensity and pupil diameter
- [Supplement] Explain the pupil reflex in terms of the antagonistic action of circular and radial muscles in the iris
- [Supplement] 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
- [Supplement] Describe the distribution of rods and cones in the retina of a human
- [Supplement] Outline the function of rods and cones, limited to: (a) greater sensitivity of rods for night vision (b) three different kinds of cones, absorbing light of different colours, for colour vision
- [Supplement] Identify in diagrams and images the position of the fovea and state its function
Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Sense Organs. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- Which part of the eye refracts light as it enters? A. retina B. cornea C. optic nerve D. blind spot Answer: B
- The part of the eye that controls how much light enters the pupil is the: A. lens B. retina C. iris D. cornea Answer: C
- In bright light the pupil: A. gets larger B. gets smaller C. stays the same D. disappears Answer: B
- To focus on a near object the lens becomes: A. thinner B. fatter C. flatter D. it does not change Answer: B
- Cones in the retina are mainly responsible for: A. night vision B. colour vision C. detecting sound D. controlling the pupil Answer: B
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Recommended Books
Practice Mock Questions
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