Teacher Notes
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Teacher Notes![]() Human Reflex StudyStudent Laboratory KitMaterials Included In Kit
Cotton balls, 20
Reflex hammers, shared, 5 Transparency sheets, 15 Additional Materials Required
Gloves
Stopwatch or watch with second hand Safety PrecautionsExercise caution when performing these activities. Do not strike your partner with excessive force when using the reflex hammer. If a reaction is not observed, try again in a slightly different location but do not hit harder. Do not throw any other objects besides cotton balls at the transparency sheets. Wash hands thoroughly with soap and water before leaving the laboratory. Please follow all laboratory safety guidelines. DisposalAll materials may be stored for future use. Lab Hints
Teacher Tips
Correlation to Next Generation Science Standards (NGSS)†Science & Engineering PracticesConstructing explanations and designing solutionsDisciplinary Core IdeasMS-LS1.D: Information ProcessingHS-LS1.A: Structure and Function Crosscutting ConceptsCause and effectStability and change Performance ExpectationsMS-LS1-3. Use argument supported by evidence for how the body is a system of interacting subsystems composed of groups of cells. Answers to Prelab Questions
Sample Data{11011_Data_Table_1}
Answers to Questions
ReferencesSilverthron, D. Human Physiology: An Integrated Approach; Pearson Benjamin Cummings: San Francisco, CA; 2004; p. 437. Recommended Products
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Student Pages
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Student Pages![]() Human Reflex StudyIntroductionYou pick up a pan by the handle and almost simultaneously you realize it is hot and drop it. The act of letting go of the pan is a reflex. Investigate several common reflexes to learn how the nervous system works to deliver messages. Concepts
BackgroundA reflex is a response to a stimulus that works to return the body to homeostasis. Reflexes can occur both consciously and subconsciously. An example of a conscious reflex would be quickly removing your hand from scalding water. A subconscious reflex would be the pancreas increasing or decreasing enzyme secretion in response to changes in the concentration of the enzyme. {11011_Background_Figure_1}
To perform a test of the knee jerk reflex, the subject sits on the edge of a table so that his or her lower legs hang freely. The patellar tendon below the knee cap is lightly struck with a reflex hammer causing the quadriceps muscle to stretch. As this muscle stretches, sensory fibers send a message to the CNS via interneurons. In response, the CNS sends a signal to the motor neurons that control the contraction of the quadriceps muscle. This signal causes the quadriceps to contract and we observe the lower leg kicking outward. Flexion reflexes are pathways that trigger us to avoid painful stimuli such as a hot stove or sharp object. When a bare foot steps on broken glass, the pain receptors, called nociceptors, in the foot send the sensory message to the spinal cord portion of the CNS. The signal diverges into multiple interneurons. The interneurons activate motor neurons which trigger withdrawal from the painful stimulus. For safety reasons flexion reflexes will not be tested in this activity. Experiment OverviewThe purpose of this activity is to observe the innate reflexes our body performs to maintain homeostasis. Materials
Cotton ball
Gloves Reflex hammer (shared) Stopwatch or watch with a second hand Transparency sheet (acetate) Prelab Questions
Safety PrecautionsExercise caution when performing these activities. Do not strike your partner with excessive force when using the reflex hammer. If a reaction is not observed, try again in a slightly different location but do not hit harder. Do not throw any other objects besides cotton balls at the transparency sheets. Wash hands thoroughly with soap and water before leaving the laboratory. Please follow all laboratory safety guidelines. ProcedureNote: The reflex hammers are shared among all groups. Observe each reaction and record the responses on the Human Reflex Study Worksheet.
Student Worksheet PDF |