Light stimulus
- 1. A receptor receives information from the environment. They can be classified according to the type pf stimulus they respond to. Receptors are traducers: they convert the Energy of the stimulus into the kind of energy the nervous system can deal with (electrical impulses). Receptor type Responds to stimulus Example in humans Photoreceptor Light Rod cells in retina of eye Chemoreceptor Chemicals Taste buds Thermoreceptor Changes in temperature Thermoreceptors in skin Mechanoreceptor Mechanical changes Hair cells in ear.
- 3. Unicellular organisms and plants. Photoreceptor pigment inside the cell.
- 4. Worms
- 5. Planarian Light sensitive eyespots (ocelli) Only sense variations in light´s intensity. They can detect where the light is coming from.
- 6. Mollusks Discriminates simple shapes.
- 8. Receptors may need help in receiving the stimulus. They are often grouped together with other tissues to form a sense organ. The other tissues allow the receptor cells to work efficiently.
- 9. Simple eye Processes some images and detects shapes.
- 10. Insects Compound eyes: consists of numerous separate light- sensitive units (ommatidia). All these images generate an overall picture. Very useful in detecting movement.
- 11. Vertebrates
- 13. Laterally located eyes: the animal perceives a wide picture of its surroundings.
- 14. Frontally located eyes. 3D imaging allows better asessment of target´s position and field´s depth.
- 15. Find the function for the underlined structures: