Explaining Electrical Conductivity in Neurons!

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Objective

Students will plan and conduct an investigation to describe why dissolved ions are good conductors of electrical impulses in the axon of the neuron.

Big Idea

Neurons are specialized to conduct electrical impulses using varied ion concentrations.

Introduction

Lesson Background & Justification:

       An Action Potential is the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell. This impulse generated, as a result gained momentum, propagates down the axon and finishes with the release of neurotransmitters stored in vesicles at the end of the axon. This ultimately and consequently stimulates the post synaptic cell and repeats the process so that a message may transmitted from short and long distances within the body.

        An Electrical Conductor is a substance in which electrical charge carriers, usually electrons, move easily from atom to atom with the application of voltage. As propagator electricity, the neuron requires materials that serve as good conductors to sustain function. Positive ions such Na+ or Ca+ make great conductors of the cell and are therefore utilized and demanded for the body regularly. 

         In this lesson, students explore the power of positive ions within an conductivity investigation in order to gain an appreciation for the movement of ions present (calcium, etc.) as they carry electrical impulses and to further iterate their understanding of how electrical impulses are perpetuated and sustained over great distances within the human body.

Lesson Preparations:

 In the effort to prepare for this lesson, I make certain that I have the following items in place: 

a) Materials listed on page 4 of the Neural Network Signals Lesson Plan. 

b) Student lab books.

Common Core and NGSS Standards:

SP2- Developing and using models.  

RST.11-12.3- Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or performing technical tasks; analyze the specific results based on explanations in the text.

Standards Rationale:

      Modeling is the process by which scientists represent ideas about the natural world to each other, and then collaboratively make changes to these representations over time in response to new evidence and understandings. It is intimately connected to other scientific processes (asking questions, communicating information, etc.) and improves students ability to recall scientific jargon through association. In the classroom, it is important that teachers engage students in modeling practices, to set the foundation of success in a lesson or instructional unit. In this lesson modeling is used in concert with other science practices in the classroom to promote students’ reasoning and understanding of core science idea presented (neuron transmission of impulse via chemical energy). 

Engage

10 minutes

Section Instructional Sequence: 

         In this section of the lesson, my goal is to jog students' memories of the molecular events that are required to ensue an action potential. This activity proceeds as follows:

a) State: We are going to take a look back at the action of nerve cell per video and serve as narrators for the video that we see. Play the following video Neural Impulse Video with muted audio and allow for one student to narrate. 

b) Repeat video 2-3 more times with other student volunteers. Fill in any holes that were left unfilled when students are done.  

Explore

40 minutes

Section Instructional Sequence: 

         In this section of the lesson, my goal is to guide students through the inquiry process and allow for them to investigate via simulation the relative conductivity strengths of ions and encourage students to apply their discoveries to explain why and how these ions are ideal to propagate an action potential in the cell (an ion dependent action). This activity proceeds as follows:

a) Slide 1: Take students through the timeline of discovery of how our brain sends messages. Advance one row at a time as you read to the students. Explain that we are going to utilize some common materials to explore this concept.  

b) Follow set up procedures and experimental procedures as described on Neural Network Signals Lesson (page 6) and provide all student pairs with a copy of this sheet. 

c) Using the materials, loosely guide students through the investigation as prescribed in the Neural Network Signals Lesson. Facilitate the investigation by posing questions to students that aid in organizing their thoughts and consequently their investigations . This should accompany questions that promote scaffolding of their activities, processes and developing conclusions. (What did you discover from step X? Do you need to run another trial? Why or why not? What are your next steps?) Discuss their discoveries as they progress from one ion solution to the next. (See Exploration in Action Video Clip)

Standards Covered:

SP2- Developing and using models.  

RST.11-12.3- Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or performing technical tasks; analyze the specific results based on explanations in the text. 

Explain

15 minutes

Section Instructional Sequence: 

         In this section of the lesson, my goal is to help students comprehend why positive ions are great conductors of electricity as witnessed in their exploration activities. This activity proceeds as follows:

 a) State: Now that we understand that positive ions make for great conductors of electricity, let's gain an understanding of why this is. Play the following video and discuss post video as it relates to their experiments. Allow student teams to report out their findings and their connections to the video and to succinctly verbally explain, using both evidence from the video and their exploration findings why and how they know that positive ions are ideal conductors of electricity. 

Ions and Conductivity:

                    

Standards Covered:

RST.11-12.3- Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or performing technical tasks; analyze the specific results based on explanations in the text.

 

Extend

15 minutes

 Section Instructional Sequence: 

         In this section of the lesson, my goal is to promote student comprehension of the relationship between and the benefits of consuming sport drinks and neural health. This activity proceeds as follows:

a) Tell students: "I heard that sports drinks like Gatorade are not only great for restoring hydration levels in athletes, but they are also good for neural health". Ask students: "Do you think that this statement has any validity? Why or Why not?" "What would we have to do in order to find out if this hypothesis is in fact truth?" Take comments and suggestions from the class. 

b) Chronicle student suggestions based on best scientific practices on the board. If the student generated list doesn't lead with research or to seek background information, affix to the top of the list and explain why. 

c) Encourage students to research the constituents of sports drinks on their phones and produce a a refined hypothesis regarding the relationship between sport drinks and neural health. Ask students:  "Based on what we have learned, what would you predict about the conductivity potential of sports drink if we tested them? Discuss. 

d) Allow for students to design a quick investigation that compares/contrast the conductivity potential of sports drink to something known to have great conductivity potential.

e) Allow students to run their investigations and discuss their results among the class. Instruct students to share if their hypothesis could potentially be refuted or supported and if more work needed to be done to solidify their findings. 

Standards Covered:

SP2- Developing and using models.  

RST.11-12.3- Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or performing technical tasks; analyze the specific results based on explanations in the text.

Evaluate

10 minutes

Section Sequence:

      In the section of the lesson, my goal is to evaluate student's understanding of conductivity in general and its relationship to powering the neuron electrically so that it can executive its specific function. I proceed as follows:

a) Direct students attention to page 4, question #5 of the  Neural Network Signals Lesson and instruct for them to respond to the question prompt individually in their lab books.

b) Once all students have completed the assignment, instruct students to swap responses and review responses with students as they peer edit and grade.

Standards Covered:  

RST.11-12.3- Follow precisely a complex multistep procedure when carrying out experiments, taking measurements, or performing technical tasks; analyze the specific results based on explanations in the text.