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Sense Receptors Sense Receptors How can you use your senses to experience an orange? Which of your senses do you use? Of course, you use your sense of sight. You can see the orange against the green leaves of the tree. Your sense of touch lets you feel the orange’s slightly bumpy skin. You hold the orange to your nose to smell it. As you peel the orange, you can hear the rind pulling off. You can see the juices as they squirt from the orange, and the smell gets even stronger. Finally, you taste the orange and feel the juices run down your chin. Every day, you rely on your senses to help you experience sense receptors the world around you and to keep you safe. Your body – things that contains sense receptors that send information to your brain detect changes in so your body can take in information and respond an organism’s appropriately. environment What are some special sense receptors? While we talk about the five senses—taste, touch, sight, hearing, and smell—we actually have other senses. Do you have to put your hand in the fire to feel the heat? No, of course not! You can be sitting several feet away and still feel the heat from the campfire! Your skin contains special sense receptors, called thermoreceptors, that gather information about the temperature of the environment and inform your brain. Thermoreceptors can register both heat and cold. This ability protects you from possible danger, such as being burned. Many animals use thermoreceptors to help them find prey and protect themselves from predators. Pit vipers, including all rattlesnakes, are a group of snakes that use thermoreceptors. You can see the thermoreceptors located on either side of the pit viper’s head, halfway between the eyes and the nostrils. These pits help the snake figure out the distance and direction of its prey. The snake can sense the body temperature of its prey. The snake knows where its prey is based on which pit is warmer. 1 Sense Receptors Your sense of taste uses other specialized sense receptors, called chemoreceptors, that sense the different chemicals in the food you eat and send the information to your brain. The chemoreceptors help you identify what you are eating and provide you with a memory of the flavor. Can you imagine being a butterfly? Their chemoreceptors are in their feet! This way they are able to “taste” if a flower is a good place to lay their eggs. Catfish have chemoreceptors over their entire bodies so they can “taste” everything around them, including chemicals in the water. Many aquatic animals, such as sharks, have very special sense receptors, called electroreceptors. Electroreceptors allow the shark to sense other creatures in their environment. The shark has electroreceptors in pores surrounding its head and lower jaw. These receptors can sense the weak electric fields given off by other creatures. The electroreceptors are especially important in the final stages of an attack, when the shark zeros in on its prey. Shark pups, and even sharks still in the egg, use their electroreceptors to protect them from becoming another animal’s prey. The pups will hold still when they sense an electrical signal from a predator. Many aquatic creatures have electroreceptors, because electricity conducts better through water, but bees and cockroaches also have electroreceptors. Even plants have special sense receptors. The Venus flytrap is a meat-eating plant. Its two leaves are covered with little hairs. When an insect irritates two of the hairs, the Venus flytrap snaps shut, capturing a meal. Why do two hairs need to be touched? It’s in order to save the plant’s energy. Before it wastes energy to snap its leaves shut, the plant wants to be certain there will be food. 2 Sense Receptors No one likes to feel pain, but it is a protective tool for your safety. If you picked up a hot pan but did not feel the pain, you could be very badly injured. The pain signals you to let go of the hot pan. Nociceptors are the sense receptors that give you pain signals. Nociceptors are in your skin. They register dangerous pressure or temperature. The information goes to the brain, then the brain sends messages to the body part in danger. Nociceptors can register levels of hot and cold as well as levels of pressure. Even some chemicals, such as those found in chili peppers and spider toxins, can be detected by nociceptors. Now the next time you feel pain, remember it is for your own good. The pain is telling you to stop doing something harmful. Many animals travel great distances each year in migrations. The need for the animals to migrate can be caused by seasonal changes to temperature and the amount of sunlight each day. A change in the food supply can also alert animals that it is time to migrate. Many animals migrate for mating and having their young. You might be most familiar with birds such as geese that fly south during cold weather, but all kinds of animals migrate. On Christmas Island, red crabs migrate. In the Pacific Northwest, salmon leave the salt water and migrate up freshwater rivers to mate. In Africa, huge herds of wildebeest travel for food and water. The winner of migratory travel is the Arctic tern, which flies from its breeding ground in the Arctic to Arctic tern Antarctica and back every year. This is an average round trip of over 40,000 miles! Scientists are still researching how animals are able to make these journeys. Some believe there is some form of internal compass that allows the animals to use Earth’s magnetic forces. Other animals are taught the route by parent and adult animals, and they hold the information in their memories. A brown bear taking advantage of the salmon migration 3 Sense Receptors Take some time to explore how plants have their own type of receptors: 1. You will need a packet of morning glory seeds, a garden pot, soil, and a water dropper. 2. Add soil to the pot so the pot is about three-fourths full. Plant the morning glory seeds. The seeds should be spread out evenly on the surface of the soil. 3. Place the pot in a sunny place. Squeeze a few drops of water into the soil until damp. Keep the soil damp by adding a little water each day. 4. Watch the growth of the morning glories for at least 1 week. Record your observations. 5. What did you notice about how the morning glories grew? Why do you think this is so? What happens if you turn the pot around? 6. Research plants to find out the name of this activity. Do plants have any other responses to their environment? 4.
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