AP Biology Senses Lab Names Per. Our senses are constantly bombarded with various stimuli from the environment, which are relayed to the central nervous system where the information is interpreted. In the following activities you will investigate the sensitivity and limitations of your sense receptors including chemoreceptors, photoreceptors, and thermoreceptors. Sense receptors are sensitive to various stimuli such as heat, cold, pain, touch, pressure, chemicals, light, and sound. They change the energy of the stimulus into electrochemical energy. Traveling at a rate of 300 feet per second, nerve impulses move along neurons to the brain for interpretation. Not all stimuli are detected equally. In these activities you will discover some of the ways your senses are limited. **USE SPECIAL CAUTION DURING THIS LAB, PARTICULARLY WITH TASTING SOLUTIONS, TOUCHING THE SKIN WITH PROBES, AND MEASURING AROUND THE EYES. IF AT ANY POINT YOU FEEL YOU CANNOT PERFORM THIS LAB, DO NOT DO SO.** Part A: Flavor Discrimination 1. Have your partner place either a slice of potato or a slice of apple on your tongue without telling you which one it is 2. Leave the slice on your tongue for 10 seconds without sucking, chewing, or moving the slice. 3. Guess which food is in your mouth. Have your partner record whether the guess was correct. 4. Repeat steps 1-3 again under the same conditions, each time choosing either an apple or potato. Perform each trial twice, but be random in the order the trials occur. 5. Repeat steps 1-4 again for scenario 2 and scenario 3 Scenario Scenario 1 Eyes Closed No Sucking/Chewing No Nostril Breathing Scenario 2 Eyes Closed Chewing No Nostril Breathing Scenario 3 Chewing Nostril Breathing Trial (perform in random order) Apple trial 1 Apple trial 2 Potato trial 1 Potato trial 2 Apple trial 1 Apple trial 2 Potato trial 1 Potato trial 2 Apple trial 1 Apple trial 2 Potato trial 1 Potato trial 2 Guess: Correct or Incorrect
Part B: Touch Receptors Touch receptors are not evenly distributed over your skin; they are more concentrated in some areas of the body. Some touch receptors are more sensitive than others. A stimulus must be strong enough for a receptor nerve to notice and respond. This is called the threshold. 1. Tape 2 toothpicks together so they are 3mm apart. Make sure to use a ruler and that the tips of the toothpicks are even with each other. Write 3mm on the tape. 2. Prepare 5 additional sets at distances of 6mm, 9mm, 12mm, 15mm, and 18mm 3. Ask your partner to close their eyes. 4. Use the sets of toothpicks IN RANDOM order and touch your lab partner s skin GENTLY on the areas shown in Data Table 3. 5. Note whether your partner can distinguish that you are using one vs two toothpicks. Record the accuracy of their answers in the table below. 3 mm 6 mm 9 mm 12 mm 15 mm 18 mm Fingertip Back of Hand Palm of Hand Arm Back of Neck Part C: Vision Much of what you know about your surroundings is learned through sight. Your eye focuses light on the light-sensitive inner layer called the retina, which contains specialized photoreceptors called rods and cones. Rods are used mostly at night and to help you see black and white, while cones are used for color vision and sharp images. There are no rods or cones at the place where blood vessels and the optic nerve attaches to the retina; no vision occurs there. You do not see a hole in your field of vision because your brain fills in this hole as it receives information when you move your eyes 1. Sit facing your lab partner. Look into their eyes. 2. Have your partner close both eyes and hold their hand over them for 30 seconds. 3. Instruct your partner to open their eyes and quickly observe pupils and irises. Record observations in table below. Beginning Observations Pupil Reflex Observations Ending Observations
Part D: The Blind Spot 1. Hold the blind spot card (marked with + and *) at arms length with the dot on the left and the plus sign on the right. 2. Close your left eye and focus your right eye on the dot. 3. Keep focused on the dot and slowly bring the card closer to you. The plus sign will disappear when the image crosses the blind spot. Have your partner measure this distance and record it in Table 5. 4. Continue moving the card closer to your face until the plus sign reappears. Have your partner measure this distance and record it in Table 6. 5. Repeat this procedure with your right eye closed, the card flipped, and your left eye focused on the dot. Blind Spot Measurements (in cm) Distance to when + disappears Distance to when + reappears Right Eye Left Eye Part E: Afterimage When cones in the retina continually receive white or bright c colors, the chemicals in them become bleached out temporarily. The neurons in the cone cells cannot be used again until the photosensitive pigments are replaced. When this happens, your brain interprets this as darkness. Primary colors will appear as opposite colors in what is known as afterimage. 1. Stare at the red image on the index card for one minute without looking anywhere else. Try your best not to blink. Make sure your partner helps remove other distractions. 2. When the one minute is up, quickly look at the sheet of plain white paper. You should observe an afterimage. Record the color you observe in table below. 3. Repeat steps 1-2 using the blue, green, and yellow labels and record your results. Color of Label Color of AfterImage Red Blue Green Yellow
Part F: Reaction Time Reaction time is a measure of the time it takes for your brain to process information received from the sensory organs and transmit the information to the muscular system. 1. Sit facing your partner. Have your partner hold the top of a meter stick (the end with the highest numbers). 2. Hold your thumb and index finger about 2.5 cm apart at the zero mark without touch the stick. 3. Have your partner warn you verbally and then drop the stick. As soon as it begins to fall, catch the stick with your thumb and forefinger. 4. Note the distance the meter stick fell by recording the number underneath your thumb and index finger on Table X. 5. Repeat steps 1-4 two more times, recording the information each trial. 6. Repeat steps 1-5, only follow the requirements in the table. 7. Graph your results below. Include all necessary labels. Trial 1 Trial 2 Trial 3 Average Trial 1 Trial 2 Trial 3 Average Looking and with verbal warning No looking, but with verbal warning Looking, no verbal warning No look or warning (subconscious guessing)
Part G: Sound Sound causes vibrations of surrounding air. As sound waves reach the eardrum, they cause it to vibrate. These vibrations are passed along to three small bones which connect with the oval window in the inner ear. Fluid in the inner ear begins to vibrate, causing hairs to bend. Nerve endings at the hairs receive this stimulus and convert it to an electrical signal, which the brain interprets as sound. Most sounds you hear reach one ear before the other one and they sound louder in one ear than the other. Your brain can tell the difference between these sounds and tells you where the sound is coming from This procedure will be demonstrated in class. Condition Eyes Closed only Eyes and Left Ear Shut Eyes and Right Ear Shut Both Eyes/Ears Shut Guessing Direction (+ = right, - = wrong) Trial 1 Trial 2 Trial 3 Post Lab Questions 1. Which trial is easiest to distinguish between apple and potato? Which is hardest? Why is this the case for these two scenarios?
2. What do the results of the first experiment tell you about the relationship between your taste senses and olfactory senses? 3. Which skin areas tested showed the most sensitivity to touch? 4. What do you results tell you about the concentration of touch receptors in these areas? 5. Why does your blind spot not interfere with your vision? 6. Why should you wear sunglasses when the doctor dilates your pupils? 7. Interpret your reaction time graphs. What are they telling you about brain and eye and hand coordination and reaction times? 8. At which direction did you locate sound most accurately? Explain your answer Final question to be answered in a paragraph of no less than 6 sentences 9. Imagine you are in a totally darkened room so that your sense of sight is effectively eliminated. Describe how you would investigate this room using your other senses.