1. Living Systems
Investigation 4, Part 1 –
Stimulus/Response

2. Behaviors
What kinds of behaviors do you know about that help an organism survive?
Living Systems, 4.1: Stimulus/Response
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3. Instinctive vs. Learned Behavior
Most behaviors involve a response to something in the environment. Some behaviors are instinctive; an animal exhibits an instinctive behavior from birth, such as when a rabbit runs away from a predator. Other behaviors are learned, such as a bear learning to jump into a river in response to seeing a salmon swimming by.
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4. The Respiratory System and Breathing Response
When you exhaled all your air into the lung volume bag, what was your body's response?
Living Systems, 4.1: Stimulus/Response
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5. The Respiratory System and Breathing Response
Why did you immediately take in a big breath? Exhale completely and hold your breath. What does this feel like?
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6. The Breathing Response
How do your lungs know when to breathe?
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7. The Breathing Response
Breathing is an instinctive response to a signal, called a stimulus, sent by your brain stem in response to a buildup of carbon dioxide in the blood. The carbon dioxide-sensing system in your brain stem works continuously to send stimuli to your respiratory system, which commands, "Breathe, breathe, breathe."
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8. Stimulus and Response
A stimulus is an interaction between some action in the environment and a receptor in the central nervous system. The nervous system is a complex collection of interacting organs and tissues made of cells called neurons.
When sensory input triggers (starts) an action, that input is a stimulus, and the action it triggers is the response.
What kinds of things might be a stimulus to trigger an action?
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9. Reading in Science Resources
Living Systems, 4.1: Stimulus/Response
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10. The Brain and Nervous System
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11. Focus Question How do humans respond to dangers in the environment?
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12. Falling Cup
What was the stimulus that caused the student to start moving the hand?
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13. Falling Cup
We call this kind of stimulus a visual stimulus. Pulling the hand out of the way is a response.
Name some examples of other stimuli. What response might you expect to happen with each stimulus?
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14. Build a Falling-Cup Device
Materials 2 cups 2 lids 2 dowels 2 binder clips
Procedure
Work in pairs to construct a falling-cup system.
Practice responding to the falling cup.
Use both your right and left hands.
Switch partner roles.
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15. Change the Drop Distance
Work with your partner to see how close to the desktop you can position the cup and still escape when you see it start to fall. Use a meter tape to measure the distance from the desktop to the cup. Reposition the binder clip so you can return to the same starting point. Record the distances you have tried. Work on releasing the cup smoothly. Don't give any clues to the responder that you are about to drop the cup! You can tape a piece of paper to the cup to hide your hand.
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16. Standard Release Height
We need to set a standard release height so that it is a challenge to get your hand out of the way. Discuss in your groups what our class standard should be. Average suggested height: _______ . We will use this height as our standard release height for future investigations.
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17. Stimulus/Response Recording
Fill in the height of drop, stimulus, and response.
One person is the cup releaser; the other is the responder.
Record an "X" in the "Hit" column if the cup hits the responder's hand; record misses in the "Miss" column.
Start recording at the bottom of the column and move up. The releaser records on the responder's data sheet.
Drop and record until there are either five hits or misses.
Change roles and repeat the investigation.
Use a new data box to record results for your left hand.
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18. Foot-Response Time
Do you think your foot-response time is faster or slower than your hand-response time? Design an investigation to find out. Standard Release Height: ______
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19. Stimulus/Response Data
Which body part responded more quickly to the falling cup? Which was slower? Why might that be the case? Is there a difference between your right and left hand? Why might that be? Is there anything you could do to improve your response time?
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20. Clean Up! Return the materials to the materials station.
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21. Sense-Making Discussion
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22. Stimulus/Response
Discuss the relationship between a stimulus and a response in your groups. Describe the system that allows you to move out of the way of a falling object. Does it take the same amount of time for hands and feet to respond to a visual stimulus? Why or why not?
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23. Stimulus/Response
What are some examples of stimulus/response with other animals? How might a quick response time benefit an organism? Can you think of an example of a plant responding to a stimulus?
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24. Vocabulary Review
behavior the things organisms do to survive and reproduce response a reaction of a living thing to a stimulus instinctive an inherited behavioral trait that an animal displays from birth stimulus something that causes an action or response
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25. Vocabulary Review
receptor cell that sends messages to the brain when it receives stimuli central nervous system where sensory impulses pass through the brain and spinal cord neuron a communication cell found in the brain and nervous system response time the length of time it takes for a person to act in response to a stimulus brain part of the central nervous system protected by the skull
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26. Focus Question How do humans respond to dangers in the environment?
Discuss the focus question in your group and then respond on your own.
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27. Does Practice Make Perfect?
Did practice make a significant difference in response time? If so, why do you think it did? What factors besides practice might affect response time?
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28. Does Practice Make Perfect?
Practice can improve response time by strengthening arm and leg muscles and reinforcing neural pathways that carry the stimulus/response message. Sometimes sickness, poor conditioning, or fatigue can slow response time. When a person's bones, muscles, nerves, and brain are working well together, we say they are well coordinated.
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29. Multimedia
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30. How do humans respond to dangers in the environment?
Wrap-Up/Warm-Up
How do humans respond to dangers in the environment?
Pair up with a partner to
share your answer to the focus question;
discuss how your firsthand investigations provided information to answer the focus question.
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Notebook image: © photastic/Shutterstock TM
Living Systems, 4.1: Stimulus/Response