Life Science 4.2 : Responding to the Environment

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Life Science 4.2 : Responding to the Environment

  1. 1. Life Science 4.2<br />Responding to the Environment<br />
  2. 2. Objectives:<br />List four sensations that are detected by receptors in the skin.<br />Describe how a feedback mechanism works.<br />Describe how light relates to sight.<br />Describe how the senses of hearing, taste, and smell work.<br />
  3. 3. Sense of Touch<br />Stimuli and Receptors<br />Touch is what you feel when sensory receptors in the skin are stimulated. <br />Each kind of receptor responds mainly to one kind of stimulus.<br />
  4. 4. Responding to Sensory Messages<br />Reflexes <br />Immediate involuntary actions activated by pain receptors in your skin.<br />Help you move quickly out of the way of danger.<br />Feedback Mechanisms <br />Cycles of events in which information from one step controls or affects a previous step.<br />Example : Cooling of body<br />
  5. 5. Sense of Sight<br />Reacting to Light<br />Your pupil is an opening that lets light enter the eye.<br />The pupil is surrounded by the iris, a ring of muscle that controls the amount of light that enters the eye.<br />Focusing the Light <br />Light travels in straight lines until it passes through the cornea and the lens.<br />Muscles in the eye change the shape of the lens in order to focus light onto the retina.<br />Retina is packed with photoreceptors, which are special neurons that change light into electrical impulses.<br />2 photoreceptors are rods and cones<br />Rods – sensitive to dim light – good for night vision<br />Cones – sensitive to bright light – fine details and colors<br />Impulses travel to axons in optic nerve – to the brain to be interpreted.<br />
  6. 6. Parts of the Eye<br />Common Vision Problems<br />Convex lens – nearsightedness<br />
  7. 7. Sense of Hearing<br />Each ear has an outer, middle, and inner portion.<br />Sound waves reaching the outer ear are funneled into the middle ear and then into the inner ear before being interpreted by the brain.<br />Converted to electrical impulses by neurons in the fluid of the cochlea.<br />
  8. 8. Sense of Taste<br />Your tongue is covered with tiny bumps called papillae. <br />Most papillae contain taste buds.<br />Taste buds contain cluster of taste cells, or receptors for taste. <br />Taste buds respond to sweetness, sourness, saltiness, and bitterness.<br />
  9. 9. Sense of Smell<br />Receptors for smell are located on olfactory cells in the upper part of your nasal cavity. <br />An olfactory cell is a nerve cell that responds to chemical molecules in the air.<br />

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