vision• Eyes respond to light stimulus • Convert stimuli into impulse • Brain interprets impulses • Enables you to see
Cornea clear tissue in front of eyePupil opening thru. which light enters eye Iris surrounds pupil & gives eye its regulates amt. of light color entering eyeLens focuses lightRetina layer of receptor cells 2 types of that line back of eye receptor cells: • rods- black, white, grey http://studyjams.scholastic.com/studyjams/jams/science/human-body/ • cones- colors
Because of the way in which the lens of the eye bends light rays, the image produced by the lens is upside down.
Vision problems• Nearsightedness= trouble seeing far away – Use glasses with concave lenses• Farsightedness= trouble seeing near objects – Use glasses with convex lenses
Farsightedness is usually corrected by placing a convex lens in the front eye. BEFORE AFTER
hearing• sound produced by vibrations• 3 parts of ear:• outer ear- part you can see• middle ear- eardrum-vibrates• inner ear- cochlea, semicircular canals
Sense of balance• controlled by ears- semicircular canals- full of fluid
Senses of smell & taste• Work together• Determine flavor• Chemicals trigger receptors• smell- 50 odors• 5 main taste sensations- sweet, sour, bitter, salty, umami (meatlike taste)
Test your senses of taste and smell to find out which sends the clearest message to the brain.• Materials• 6 small paper bags• 6 small scoops of mini jelly beans in three different flavors (lemon, grape, cherry)• marking pen• With the marking pen, identify the bags as either taste or smell bags. Write "taste #1," "taste #2," and "taste #3" on three of the sacks and "smell #1," "smell #2," and "smell #3" on the other three sacks.• Divide jelly beans among the bags so that you have a "taste" bag and a "smell" bag for each of the three flavors. Taste #1 and smell #1 jelly beans should be the same, taste #2 and smell #2 should be the same, and so on. Crush a few of the "smell" jelly beans so the odor molecules can escape into the bag. Close the bags by folding down the top.• Before Testing: Choose three of your classmates as testers and give them each a sheet of paper. Instruct them to draw a data table with three columns and three rows. The columns should read: "smell only"; "taste only"; and "taste and smell." The three rows should read: "flavor 1"; "flavor 2"; and "flavor 3."• Taste Test: Instruct the testers to close their eyes and plug their noses. Choose one of the taste bags and instruct each tester to chew on a sample from this bag. In five seconds, ask them to record on their data table what flavor they believe the sample to be. Repeat the procedure for the remaining taste bags. A small sip of water between samples will help clear away the previous flavor and provide a more accurate test. If they cannot tell the flavor, have them record "unknown."• Smell Test: Choose one of the "smell" sample bags. Have testers close their eyes, open the bag, and inhale the aroma for 10 seconds. Remove the bag and close the top tightly. Have your testers record the flavor of the sample on the data table. Make sure each of them repeats this procedure for the other two samples.• Smell and Taste Test: Use the "taste" bags again. Repeat the procedure as in step # 4, "Taste Test," but do not have your testers hold their noses shut. Be sure, however, that they have their eyes closed. Ask them to record their guesses in the appropriate column on their data table.• Questions• Which sense, taste or smell, identified the correct flavor most often?• How were the "taste" messages your brain received different from the "smell" messages?• How do you think candy makers simulate fruit flavors?• Why do you taste more flavor when you chew a jelly bean than when you suck on it? 5. If you took the Smell and Taste Test with your eyes open, do you think you could recognize the flavor of a purple jelly bean that has an orange flavor? What data from your tests support your conclusion?
• Think of all the wonderful sensations taste can impart to us - the delicious Thanksgiving turkey and gravy, mashed potatoes, cranberry sauce and pumpkin pie! Coffee, chocolate, lush strawberries - the list goes on and on! Receptors on our tongues bind to chemicals in our food and relay the information about the chemicals to our brain. Surprisingly, all those wonderful tastes are transmitted to our brains through only four types of receptors on our tongues - those for sweet, sour, salt and bitter. How can this be so?• MATERIALS: Life Savers or other flavored candies Have students work in pairs. One student closes their eyes and holds their nose, while another feeds them a lifesaver, without telling them the flavor. The student should try to guess what flavor the life saver is, without letting go of their nose. Observations should proceed for a minute or so as the candy dissolves in their mouth. Is there any change in the taste of the candy from the beginning to the end of the experiment? Describe the tastes. There are only four different types of true tastes - sour, sweet, salt and bitter. Each of these types of receptors bind to a specific structure of a "taste" molecule. Sweet receptors recognize hydroxyl groups (OH) in sugars, sour receptors respond to acids (H+), the metal ions in salts (such as the Na+ in table salt. Alkaloids trigger the bitter receptors - alkaloids are nitrogen containing bases with complex ring structures which have significant physiological activity. Some examples of alkaloids are nicotine, quinine, morphine, strychnine, and reserpine. Many poisons are alkaloids, and the presence of receptors for the bitter taste at the back of the tongue may help to trigger the vomiting response. Approximately 80-90% of what we perceive as "taste" actually is due to the sense of smell. Just think about how dull food tastes when you have a head cold or a stuffed up nose. At first students may not be able to tell the specific flavor of the candy, just perhaps a sensation of sweetness or sourness. If students are patient, some may notice that as the candy dissolves they can identify the specific taste. This is because some scent molecules volatilize and travel up to the olfactory organ through a "back door" - that is up a passage at the back of the throat and to the nose. Since we can only taste four different true "tastes", it is actually smell that lets us experience the complex, mouth watering flavors we associate with our favorite foods.
TRY THIS ACTIVITY• Recapture a "smell" memory. Put a number of different, fragrant items in separate paper bags--a pine bough, broken cinnamon sticks, mothballs, a cloth sprinkled with baby powder, lemons. Sniff each bag until one brings a strong memory to mind. Write about this memory.• Create a survey to identify the favorite smells and tastes of your friends. Conduct your survey and display the results on a graph. Which smells and tastes were most popular? Now place your results in a Venn diagram. Do you see any overlap between favorite smells and favorite tastes?• Can you tell the difference between an apple and a potato by using only the sense of taste? Cut an apple and a potato into the same size pieces. Close your eyes, plug your nose, and lick one of the pieces. Can you tell what it is? Next, unplug your nose and eat the piece. Can you identify it now?• Animals and insects use smells to send messages. Cats and dogs, for example, put their own personal smell stamp on objects to communicate the message "no trespassing." Ants lay down odor trails to mark the pathway to food. The monarch butterfly and ladybug produce odors that say, "I dont taste as good as I look." Research an animal by reading and thinking about how it uses smell to communicate.
sense of touch• skin= largest sense organ• contains different receptors- respond to light, touch, & pain• pressure receptors found in dermis