CSI Neuroscience: The Case of the Acetylcholine Blocker!

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Objective

Students will analyze and interpret data from the inhibition of acetylcholine to elucidate it's activity as a neurotransmitter.

Big Idea

Like removing a part from a mechanical system, the job(s) of Acetylcholine neurotransmission can be elucidated by the introduction of a blocking or inhibitory agent.

Introduction

Lesson Background & Justification:

    Neurotransmitters are endogenous chemicals that transmit signals across a synapse from one neuron to another or target neuron. Acetylcholine is one of many neurotransmitters in the autonomic nervous system (ANS). It acts on both the peripheral and central nervous systems (PNS) and (CNS) and is the only neurotransmitter used in the motor division of the somatic nervous system. Once released from the presynaptic neuron, this chemical executes 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 is to evoke an excitatory response of its receiving cell in most cases (the exception is cardiac muscle cells). In this lesson, students become familiarized with both the normal and inhibited actions of acetylcholine through the process of deduction. 

Prerequisite Knowledge: It is recommended that students be familiar with the structure and function of a neuron, the concept of neurotransmission 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 CSI: Neurotransmitter Unit Printed and Laminated Sheets (Produce 5 of each for a class of 30).  

b) Lab Materials: plastic pipettes, 5, 1ml microcentrifuge tubes labeled Ach Indicator, (filled with phenolphthalein solution) and 5, 1ml microcentrifuge tubes labeled Ach Cell Serum (filled with pH 8 Buffer Solution). 5 Indicator tubes (filled similarly to the Ach Indicator) for each of the following neurotransmitters: Dopamine, Serotonin, Adrenaline, GABA, and Glutamate. 5 Cell Serum Tubes (filled similarly to the Ach Cell Serum) for each of the following neurotranmsmitters: Dopamine, Serotonin, Adrenaline, GABA, and Glutamate.  

c) Student lab books.

d) Class set of Acetylcholine Synpase Worksheets and Brain Outline half sheets

Common Core and NGSS Standards:

SP4- Analyzing and interpreting data.

SP2- Developing and Using Models.

HS-LS13: Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.

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:

      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 (mechanisms of maintaining homeostasis of the nervous via Acetylcholine transmission and activity).

Engage

10 minutes

Section Primer: 

        Succinylcholine (Sux), also known as suxamethonium or suxamenthonium chloride, is a nicotinic acetylcholine receptor agonist, used to induce muscle relaxation and short-term paralysis, usually to facilitate tracheal intubations or lung ventilation process during surgery of the critically injured. This agent acts a depolarizing neuro-muscular blocker and prevents the neurotransmitter acetylcholine from exciting the post-synaptic cell which can be another nerve cell or muscle cells. In this section of the lesson, my goal is to introduce students to the malicious utilization of succinylcholine and stimulate them to consider why this drug is considered the "perfect murder weapon" outside of its medicinal use.    

Section Sequence:

a) Slide 1: Read the opening question as seen on the screen. As students respond, list their adjectives in the class list column of the table. When possibilities are exhausted, advance the heading and list in the second column. Share that a chemical named Succinylcholine has been bestowed this name. Compare and contrast the class list with the Sux list. Ask students if they had ever heard of this agent. Discuss and elucidate their reference points.

b) Share that Sux is controlled in medical facilities, and is generally used as a murder weapon by those who have access to it. Ask "who might be considered as a potential suspect in this case?" Discuss and share the video example below.  

c) Post video ask students if they think that there is a relationship between sux and the nervous system. Discuss as class and through a series of leading questions, prompt students to clarify which system if not the nervous system that they believe the drug antagonizes and why.  

d)  Share that they will act as CSI Agents today to investigate which neurotransmitter that this potentially deadly chemical antagonizes. 

Explore

20 minutes

Section Sequence: 

       The goal of this section is to encourage students to utilize their deductive reasoning skills and command of content to investigate the blocking activity of succinylcholine. This activity proceeds as follows: 

a) Slide 2: Share with students that they will now play the role of Forensic Chemists to ascertain the identity of the neurotransmitter that is impacted by the presence of sux in a person's system. Specify that their jobs are to analyze several tests and find out what the "victim" to sux is. Since, the toxicologists in the video had already discovered the toxin (sux) that killed the victims (children), their jobs are to discover and explain which naturally occurring chemical in the body is stymied by its presence. 

Slide 2: Direct students to obtain 1 laminated CSI data/test card, corresponding lab materials (tubes and pipettes) and explain the specifics of the exploration activity as per the directions listed. Clarify the steps while students are viewing their first test card. Give students 15-18 minutes to complete the tasks stated on the slide.

b) Take 2-5 minutes to unveil their conclusions. Encourage students to support their conclusion with evidence from their exploration activity and refute other suggestions similarly.

Students should deduce the following from their results:

    1) Test 1 (serum secreted from stimulated Ach neuron)- Acetycholine is being actively synthesized by the neuron being naturally stimulated. 

    2) Test 2 (addition of secreted serum to neuron with Ach receptors)- Determine that the cell is being stimulated by acetycholine in the serum extracted from test 1. 

     3) Test 3 (sux + serum + neuron with Ach receptors)- Determine that the activity of the acetylcholine has been impeded by the sux.

Collectively, they should deduce from the data that Ach is the victim to sux's actions. 

Standards Covered:

SP4- Analyzing and interpreting data.

SP2- Developing and Using Models.

HS-LS13: Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.

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.


Explain

20 minutes

Section Primer:

      The Neuromuscular Junction is the synpatic area that connects the nervous system to the muscular system. Similar to neuron to neuron interactions,  the muscles receive the neurotransmitter aceytylcholine via action potential generation in the pre-synpatic neuron and subsequent neurotranmssion events. In contrast,  the binding of ACh to the receptor on the muscle fiber depolarizes it, causing a cascade that eventually results in muscle contraction. The goal of this section of the lesson is provide students with a set of illustrations and corresponding content to elucidate the general set of activities driven by acetylcholine in the neuromuscular junction. This information will then be used to help students to understand the mechanisms of succinylcholine actions later in the lesson.

 Section Sequence:

a) Slide 3: Say "Now that we understand that acetylcholine producing cells are the victims of sux activity, we need to understand how this happens." Introduce students to the neuromuscular junction using the image and prompt students to use the information from the medical label above the image to infer where sux docks to perform its actions.

b) Slide 4: Share that in order to understand the dangers of this drug, we must understand the mechanics of the system that is under siege. Distribute the Acetylcholine Synapse Worksheet to all students and give them 10 minutes to study and address the questions of the sheet with a partner. Review for accuracy. 

c) Ask: based on the activities listed on the sheet, can you predict which parts of the brain that are loaded with acetylcholine receptors? Take responses, and make certain that students edify their responses with information from the worksheet. 

d) Slide 5: Distribute Brain Outline half sheets to each student and share that the diagram on the screen highlights the impacted areas of the brain. Instruct for them to highlight these areas on the illustration to record the abbreviation Ach next to each part listed that employs Ach as an excitatory neurotransmitter. Validate correct predictions of students. 

Extend

30 minutes

Section Sequence:

      In this section of the lesson, my objective is to encourage students to infer specific blocking mechanisms of sux based on its structure compared to that of acetylcholine (sux is the fusion of two acetylcholine molecules). They then create visual predictions of prevented actions in either the pre or post synaptic cells. This activity proceeds as follows:

a) Slide 6: Share that we are examining the molecule Ach on the left and Sux on the right. Based on structure alone, can you predict why Sux is as indicated by our lab results, an antagonist in the Ach nuerotranmission pathway? Discuss and allow students to use the board clarify their thoughts.

b) Slide 7: Ask: Based on our discussions from the previous slide, describe the actions that are prevented in the diagram when a person is exposed to Sux? Discuss 

c) Slide 8: Distribute two copies of the blank synapse diagram to each student. Instruct them to cut out the outline of each image and glue into their lab books side by side (with some spacing) as seen on the screen. Distribute one copy of the sux molecule to each student from the Succinylcholine Molecule sheet and instruct students to create a visual representation of normal Acetylcholine neurotranmission on one diagram and one that expresses Ach transmission when introduced to Sux on the other. Students at this point are to explicitly infer the position (bound to a specific protein) of the sux molecule to explain the activity being illustrated. Students should annotate illustrations for transparency of thought.

d) Slide 9: After 20 minutes, use the diagram on this slide to clean up any misrepresentations that students may have. Help students to understand the nature of an antagonist. Check with students to see if they had predicted the drug's actions correctly and if not, prompt for an understanding of those who had incorrect predictions. 

Standards Covered:

SP2- Developing and Using Models.

HS-LS13: Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.

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

10 minutes

Section Sequence:

a) Slide 10: Read the expectations of the students exit ticket activity and collect at the conclusion of class. Grade based on students scientific justification of their asserted opinions. 

Note: In addition to their opinion, students should be able to support their responses with meaningful content. For example if they say yes that it should be regulated, they too should be able to state that sux interferes with an important and specific excitatory molecule (indicating that they acknowledge that there are other excitatory molecules) that stimulates neurons to communicate with muscle cells in the heart and the body. This consequently leads to the compromised activity of these muscles and ultimately death. 

Standards Covered: 

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.