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5.2: Using Reflexes: Neurons in Action – Student Edition (Human Biology)

Difficulty Level: At Grade Created by: CK-12
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Discuss the role of models science-especially models of the brain and spinal cord.

Draw students' attention to the Key Ideas using means such as posters and transparencies.

Begin this section with Mini Activity: The Knee Jerk Reflex and relate to the first Did You Know?

Demonstrate and introduce the 5-part sequence of a reflex arc using your hand.

Do the Activity 4-1: How Fast Is Your Reaction Time?

The Knee Jerk Reflex If possible, borrow one or more physician's reflex hammers for students to try. Students elicit knee jerks by tapping on their own quadriceps tendons below the kneecap. Taps should be sharp and abrupt, but not too hard.

Questions and Answers

  1. What makes it easy to get a knee jerk reflex?
  2. Which muscles contract when your knee jerks?
  3. How hard must you tap to get your knee to jerk?
  4. What happens if you squeeze your hands together when someone else taps your knee?
  5. Can you stop your foot before it swings, if you want to?
  6. Name some other reflexes.
  7. Why are reflexes important?
  8. Have students draw a picture of the knee jerk reflex.

A suggested response will be provided upon request. Please send an email to teachers-requests@ck12.org.

How many reflexes can you think of? Work in small groups or in pairs to list as many as you can. Group them into categories that show how the reflexes protect you. Decide which are easier to control than others. Then share your list with the class.

Identifying Parts of a Reflex Students pick two reflexes from the list of reflexes they created in the Apply Your Knowledge question of page 32 and identify the five parts of those reflex arcs.

React First, Think Later Students calculate the time it takes for a nerve impulse to go from their big toe to their spinal cord and then from their spinal cord to their cortex.

A suggested response will be provided upon request. Please send an email to teachers-requests@ck12.org.

Sometimes in addition to tapping your knee to make sure you have healthy reflexes, the doctor tickles the bottom of your foot. Why is that?

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Date Created:
Feb 23, 2012
Last Modified:
Apr 29, 2014
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