DO NOW :

1. DO NOW: 4/11 List the 5 senses and an organ associated with each sense. Then list an object detected by each sense. (Ex. Ear and a bell) • Objectives: • List 4 sensations that are detected by receptors in the skin. • Describe how a feedback mechanism works. • Explain how light relates to sight. • Describe how the senses of hearing, taste, and smell work.

2. Sense of Touch • Stimuli and Receptors • There are various sensory receptors on your skin that allow you to feel. • The different types of receptors respond to different stimuli.

3. Responding to Sensory Messages • Pain receptors in your skin activate immediate, involuntary actions called reflexes. • Reflexes help you move quickly out of the way of danger.

4. Responding to Sensory Messages (continued) • Feedback Mechanisms are cycles of events in which information from one step controls or affects a previous step. • Feedback Mechanisms allow our body to maintain homeostasis. • Examples: • Heart rate increases with vigor exercise but returns to normal after you slow down. • When we get hot we sweat to cool down. • When we eat something our pancreas releases insulin to regulate our blood sugar levels.

5. Sense of Light • Reacting to Light • You see an object when it reflects light toward your eyes. • Your eye is covered by a cornea that protects the eye but allows light to enter the eye. • Your pupil is an opening that lets light enter the eye. • The pupil is surrounded by the iris, a ring of muscle that controls the amount of light that enters the eye. • Light then travels through the lens to the retina, a layer of light-sensitive cells.

6. Sense of Light • Focusing the Light • Light travels in straight lines until it passes through the cornea and the lens. • Muscles in the eye change the shape of the lens in order to focus light onto the retina. • The retina has many photoreceptors to change light into electrical impulses that allow our brain to recognize the images we see. • Rods: Allow us to see black and white and in the dark. • Cones: Allow us to see color and fine detail. • http://www.youtube.com/watch?v=15P8q35vNHw&feature=related

7. Sense of Hearing • Each ear has an outer, middle, and inner portion. • Sound waves reaching the outer ear are funneled into the middle ear and then into the inner ear before being converted into nerve impulses that can be interpreted by the brain. • Cochlea: A fluid-filled organ of the inner ear that change sound waves into electrical impulses that can be interpreted by the brain.

8. Sense of Taste • Your tongue is covered with tiny bumps called papillae. • Most papillae contain taste buds. • Taste buds contain cluster of taste cells, or receptors for taste. • Taste buds respond to sweetness, sourness, saltiness, and bitterness.

9. Sense of Smell • Receptors for smell are located on olfactory cells in the upper part of your nasal cavity. • An olfactory cell is a nerve cell that responds to chemical molecules in the air.

10. True or False • Rods help you see color and detail in bright light. • Cones provide a colorful view of the world. • Your brain combines signals from the senses of smell and hearing to give you a sensation of flavor.

11. Do you hear colors? • About one out of every 25,000 people has synesthesia. These people experience bled of senses. For example, one person sees blue when a particular note is played on a piano. Another person gets a very bitter taste in his mouth when he makes hamburger patties with his hands.

12. Sense of Light • http://www.youtube.com/watch?v=jdsH370Hf3s