To Be or Not to Be a Neurotransmitter: Exploring the Nature of Common Neurotransmitters!

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Objective

Students will construct an argument that supports the categorization of common neurotransmitters and critique the categorization systems of others.

Big Idea

Neurotransmitters are chemicals that are specifically designed to control brain activity, but vary in their chemistry and physiological consequence.

Introduction

Lesson Background & Justification:

    Neurotransmitters are endogenous chemicals that transmit signals across a synapse from one neuron to another. Once released from the presynaptic neuron, these chemicals execute a conservative set of cyclic activities which include: a) the induction of a response in the receiving cell, b) re-absorption into the dispensing cell and/or c) processing by specialized proteins to ascertain adequate levels of the neurotransmitter for subsequent potentials. The overall goal being to reset the neurotransmission system for continuous homeostatic actions. In this lesson, students become familiarized with the chemical nature of six common neurotransmitters and learn to classify them based on their unique physical and physiological properties. 

Prerequisite Knowledge: It is recommended that students be familiar with the structure and function of a neuron and the action potential mechanism. 

Lesson Preparations:

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

a) A class set of Neurotransmitter information cards/sheets (1 set per student groups of 2). 

b) Student lab books.

c) Class set of "Discovered: The Molecule Responsible for Itchiness" articles. 

Common Core and NGSS Standards:

MP3-Construct viable arguments and critique the reasoning of others.

RST.9-10.1-Cite specific textual evidence to support analysis of science and technical texts, attending to the precise details of explanations or descriptions. 

RST.11-12.8-Evaluate the hypotheses, data, analysis, and conclusions in a science or technical text, verifying the data when possible and corroborating or challenging conclusions with other sources of information.

Standards Rationale:

      Argumentation in the science classroom is an essential skill to help students grapple with  tough concepts and to strengthen explanations of the explored material. When students construct their own arguments to support the material engaged in and/or critique arguments of other students, the grow in meaningful forms of scientific practices. They work to make sense of scientific phenomena rather than working to replicate the understandings communicated by a textbook or other authority. Collectively, engaging in this type of discourse can alleviate the pressure of teachers feeling fully responsible for attaching meaning to information presented in the classroom. In this lesson argumentation is used in concert with other science practices in the classroom to promote students’ reasoning and understanding of core science idea presented (explaining the nature of neurotransmitters).

Engage

10 minutes

Section Primer: 

      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 gains momentum, propagates down the axon and finishes with the release of neurotransmitters stored in vesicles at the end of the axon. Neurotransmitters are endogenous chemicals that transmit signals across a synapse from one neuron to another or target neuron.Their release initiates a cascade of chemical events which ultimately and consequently stimulates or inhibits the post synaptic cell to pursue a prescribed behavior. In this section of the lesson, students learn to define what neurotransmitters are based on a set of criterion. They later apply this criteria to assess whether or not a new chemical discovered is in fact a neurotransmitter or not.

Section Sequence: 

         In this section of the lesson, my goal is to introduce students to the distinct and specific criteria that defines a neurotransmitter. The idea is to equip them with a set of parameters so that they are in position to identify a neurotransmitter within variety of contexts thereafter.  This activity proceeds as follows:          

a) Slide 1: Say "Today we continue our understanding of neuron to neuron communication. Let's begin by reviewing what we know." Share that the class will analyze a diagram and watch a very brief video to review what was learned in the prior unit. 

b) Using simple recall activation prompts "what is this?", "what is its function?", review the parts and functions of the neuron on the screen and its relationship to the graph presented. 

c) Play the video animation below once and direct students to watch in silence and to think about what processes are occurring. Play for a second round but select a few volunteers to narrate the clips. Pause the video at 17 sec., 29 sec., and 59 sec. and give each student an opportunity to describe the actions being animated aloud to the class. Students should use precise terminology to properly annotate the specifics of action potential including chemical events (eg. diffusion of sodium ions into the axon to depolarize the cell and movement of potassium ions out of the cell to repolarize the axon & the downstream effects on the movement of neurotransmitters).   

                     

 d) Post video, discuss some elements of neuron to neuron communication that hadn't been elucidated or made clear at this point. Prompt the discussion until students articulate that details from the synaptic areas aren't as clear as the action potential within the axon of each neuron.

d)  Slide 2: Ask: "How do we know that the neurotransmitters secreted from the first neuron creates a biological response in the second?" Discuss. In the discussion, students should share or be verbally prompted to share the observations of the progression of an electrical impulse witnessed in the opening of the video as well as the the transmission of the "glow" at the end of the video observed from one neuron to the next when the neurotransmitters where released. This implies upstream dependency and that there is a factor (Nt) responsible for this transmission.  State: "The man seen here is the first person credited for discovering neurotransmitters and establishing its role in cell communication. Let's see how he came to this understanding without even seeing the actions that he proposed had taken place." Play the following video and pause at 2:12. Ask: What do you think that he discovered? Briefly discuss and resume video.

     

 e) Post video, ask students what they think “Vagusstoff” is now referred to as. Discuss and share as some point that is acetylcholine, a small molecule neurotransmitter.

Standards Covered:

MP3-Construct viable arguments and critique the reasoning of others.

Explore

30 minutes

Section Sequence:

        In this section of the lesson, my goal is to provide students with any opportunity to explore the diverse chemical nature and actions of several common neurotransmitters via a simple classification activity.The idea is to encourage students to independently build their own understanding of neurotransmitter potential prior to sharing the strict criteria that defines them in the subsequent section of this lesson and to see if they too uncover one the criterion accepted today. This activity proceeds as follows:

a) Slide 3: Say: "Now that we understand how neurotransmitters were discovered and are familiar with the activity of one, let us see how other discovered neurotransmitters compare and contrast." Distribute neurotransmitter cards/sheets to students in groups of 2 and read the directions for the exploration activity from the screen. Give students 15-20 minutes to complete this task. 

Clarification of Task: As it relates to the following tasks:

Using the information on each card, explore three different ways to classify your neurotransmitters. Record your diagrams/classification charts  in your lab books.

Share with students that they can take various approaches to develop their classification systems. This includes but is not limited to: molecular structure, molecular make up, function in the body, potential toxic affects, medical conditions that the Nt is implicated in, etc. Verbally direct them to and physically demonstrate where this information can be found as well. The goal here is for students to gain an appreciation of chemical form and specialized function of neurotransmitters. 

Switch lab books and critique another’s system.  

Student critiquing should be limited to the level of ease that they experience when navigating someone else's system and presentation of factual information. For example, students can be instructed to select the names of one of the Nt's presented at the end of the key being critiqued and work backwards to assess the validity and accuracy of the categories used to specifically classify the Nt in question as they move about the dichotomous key. 

b) Slide 4: Verbally request for students to share out their categorization criteria and record them on the board or screen. Encourage student participation by selecting specific students and requesting for them to share one way that they categorized their Nts and eventually make all calls for students to share who haven't prior to the classroom all call. Discuss overlapping ideas and instruct the class to build a set of criteria (based on the stronger of the terms list on the board) that may potentially define what a neurotransmitter is. Record this list on the board and instruct students to record the list in their lab books. 

Standards Covered:

MP3-Construct viable arguments and critique the reasoning of others.

Explain

15 minutes

Section Primer:

        Neurotransmission also referred to as Synaptic Transmission, is the process by which signaling molecules called neurotransmitters are released by a neuron (the presynaptic neuron), and bind to and activate the receptors of another neuron (the postsynaptic neuron). Chemical Neurotransmission specifically subscribes to the life cycle of the neurotransmitter itself. The steps in chemical neurotransmission are as follows:

Step 1. Neurotransmitter Biosynthesis
Step 2. Neurotransmitter storage
Step 3. Neurotransmitter release into synaptic/junctional cleft
Step 4. Interaction with neurotransmitter receptors
Step 5. Termination of neurotransmitter action (uptake, metabolism)

Section Sequence: 

         In this section of the lesson, my goal is to edify the definition of a neurotransmitter and describe the cycle of chemical neurotransmission. This activity is presented via a set of scientifically accepted criterion and proceeds as follows:

a) Slide 5: Share with students that they will learn how their ideas align with those in the scientific community. State: "If someone like Loewi discovers a molecule nowadays and then claim it to be a neurotransmitter, then the chemical must meet the following chemical and behavioral criterion". Advance each line individually. Read and address questions for each statement. 

b) Slide 6: Say "As neurotransmitters are extremely important to us for processing our environmental stimuli and regulating our internal systems, we must utilize, conserve and recycle them. We achieve this through a process called chemical neurostransmission." Draw students attention to the image on the screen and explain that they will interpret the diagram as a class to build an understanding of the process. Lead by starting to the left of the diagram and share that neurotransmitters are synthesized in the cell body and work the class's attention to the right of the screen. In the end, be certain to label the distinct steps of the neurotransmission process correctly as students interpret and record their corresponding activities.  

Standards Covered:

RST.9-10.1-Cite specific textual evidence to support analysis of science and technical texts, attending to the precise details of explanations or descriptions

Extend

20 minutes

Section Primer: 

        An itch is defined as an uncomfortable sensation on the skin that causes a desire to scratch. In 2013, scientists discovered the root of this perturbation to be Nppb (natriuretic polypeptide b), a neurotransmitter. As it is it counter intuitive for students to relate such a sensation with something that is responsible for brain activity (although there are other responsibilities), it serves as a great example to put the neurotransmitter criterion to the test. In this part of the lesson, students read a brief article on the chemical and assess its position as a neurotransmitter. 

Section Sequence:

           In this section of the lesson, my goal is to extend and challenge student's understanding of what neurotransmitter is by investing them in a scientific read which presented an explanation to the biology of an itch. This activity proceeds as follows:

a) Slide 7: Ask: What is an itch? Discuss. Where do you think it comes from and why they persist? Discuss Do you think itching is related to your nervous tissue? Explain. Discuss. Share that you are now going have them address these questions via a brief scientific article. Distribute the following article Discovered: The Molecule Responsible for Itchiness to each student. Direct their attention to the question at the bottom of the screen and instruct them to read the article, record their claim and to highlight their evidences in the physical article. After 10 minutes, share out as a class with emphasis on supporting their claims. 

Standards Covered:

MP3-Construct viable arguments and critique the reasoning of others.

RST.9-10.1-Cite specific textual evidence to support analysis of science and technical texts, attending to the precise details of explanations or descriptions

RST.11-12.8-Evaluate the hypotheses, data, analysis, and conclusions in a science or technical text, verifying the data when possible and corroborating or challenging conclusions with other sources of information.

Evaluate

15 minutes

Section Sequence:

           In this section of the lesson, my goal is to see if students comprehend the nature of neurotransmitters and how they are recycled for continued propagation in the body. This activity proceeds as follows:

a) Distribute the Classifying Neurotransmitters Evaluation hand out to each student. Instruct for them to work independently and submit as an exit ticket for the day. (See student examples for correct responses)

Standards Covered:

MP3-Construct viable arguments and critique the reasoning of others.

RST.9-10.1-Cite specific textual evidence to support analysis of science and technical texts, attending to the precise details of explanations or descriptions