Heavy Metal, It's Not your Neuron's Music!

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Objective

Students will develop a model that explains how heavy metals like mercury circulate in the environment and accumulate to toxic levels in the human brain.

Big Idea

Mercury is a heavy metal that when accumulated and ingested in high quantities disrupts the Central Nervous System of humans.

Introduction

Lesson Background & Justification:

    Mercury poisoning is a type of metal poisoning and a medical condition caused by exposure to mercury or its compounds. Mercury is a heavy metal occurring in several forms. All of these, except elemental liquid mercury produce toxicity or death with less than a gram. Toxic effects include damage to the brain, kidneys and lungs. Mercury poisoning can result in several diseases, including acrodynia (pink disease)and Minamata disease. In this lesson, students become acclimated to content that demonstrates mercury's point of entry in the ecosystem, and it's accumulative affect on the organism's nervous systems that reign at the top of food chains. 

Prerequisite Knowledge: It is recommended that students be familiar with the structure and function of a neuron, the concept of neurotransmission, the action potential mechanism and metabolic process of cellular respiration, enzyme structure and function and organelle function. 

Connection to the End of Year Student Research Project: This lesson has been inserted upstream of student research project execution to satisfy the following objective:

1) Expose students to the chemical nature and physiological effects of heavy metals in organisms so that they are able to develop research questions and hypothesis for their research projects if they elect this chemical over their other options of BPA, or Nicotine. (See student Brainstorming Ideas Attached)

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 Science Take Out's Mercury Poisoning Lab (1 copy of the student lab per student pair) 

b) Student lab books.

Common Core and NGSS Standards:

SP1- Asking questions (for science) and defining problems (for engineering).

SP2- Developing and Using Models.

SP4- Analyzing and interpreting data.

MS-LS1-3-Use argument supported by evidence for how the body is a system of interacting subsystems composed of groups of cells. 

MS-LS2-3-Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem.

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 (understanding mercury poisoning.)  

Engage

10 minutes

Section Primer:

         Minamata disease  is a neurological syndrome caused by severe mercury poisoning. Symptoms include ataxia, numbness in the hands and feet, general muscle weakness, narrowing of the field of vision, and damage to hearing and speech. In extreme cases, insanity, paralysis, coma and death follow within weeks of the onset of symptoms. A congenital form of the disease can also affect fetuses in the womb. In this section of the lesson, students are introduced to an overview of the source, cycling and impact of mercury metals on the nervous system of humans and animals. The goal, is to provide students with an example of how metals in the environment can impact how our CNS and PNS systems so that they may be informed when presented with selections for their end of year research projects.  

Section Sequence:

a) Slide 1: Present the image to the student and ask the question that accompanies the image. Allow students to only provide one word responses and collect a total of ten. Share that they will watch a clip that can help to add clarity to the events surrounding the picture. Then proceed to play the following video:

                    

b) Post video, repeat step a and ask students to compare and contrast their lists to see if their experiences pre video prepared them to interpret the image based on its history. Share that they will further their understanding of how this metal is cycled and impacts the nervous system in detail. 

Explore

45 minutes

Section Sequence:

     In this section of the lesson, my goal is to provide students with a simulation experience that helps them to refresh their memories on energy transfer in an ecosystem, while simultaneously introducing them to the passage of a nervous system antagonist (heavy metal in this scenario) within the same system. Students experience this through a myriad of activities including reading and discussing a Minamata Disease case study, constructing a food web with images/labels and simulating the accumulation of metals through trophic levels constructed in the food web. This activity arsenal is intended to raise students awareness on the mechanisms and effects of metal toxicity in the human body. This section proceeds as follows: 

Slide 2:

a) Share with students that they will execute a set of tasks that will that will further their understanding of how the metal mercury and other heavy metals are cycled through the environment and how it they consequently impact the nervous system humans. Indicate that in order to understand how this works they must learn more about ecological dynamics at the same time. Ask students if they have any idea why understanding ecosystem flow might be essential to them understanding the presence of mercury in humans. Take a few responses from the class before moving into the lab tasks outlined on the slide. 

b) Step 1: Instruct students partner pairs to obtain the Science Take Out's Mercury Poisoning  bagged kit. 

c) Step 2: Announce to the class that they will first take the opportunity to gain a little bit of background on how mercury impacts the human nervous system so that they can gain a stronger appreciation for why we are concerned about its ecological passage and/or accumulation. Instruct students to proceed with Step 3, Part 1 of the lab kit. Encourage students to use colored highlighters to discern symptoms in the reading passage for better visualization. Note that the Nervous System Function Chart comes with the kit and is only seen in the kit's content page in the attached pdf (page 3). Students should be given 10 minutes to complete this part of the activity.   

d) Step 3: Instruct students to complete task 3/part 2 of the lab from their packages and to record their responses in their lab books. Direct students to verbally summarize the results of their completed tasks to you as you circulate around the class to monitor their progress.Students should be given 15 minutes to complete this part of the activity.  (See Attached Student Sample)         

e) Step 4: In this section, students are limited on their amount of guided instruction for this activity  for the purposes of being encouraged to think their way through the modeling process. Specifically, students are directed to read and highlight pertinent information that explains the representations of a food web and mercury on page 8 which also addresses how energy and mercury travels and change through the various trophic levels of a food web. Students then utilize this information to address questions 1-5 on the same page of the manual. Thereafter, they should be instructed to make the remaining pages invisible and use the manipulatives to model the flow of energy and mercury through an ecosystem with their partners. Permit 15-20 minutes for students to work through this task. When observing students demonstrations, be certain to hold them accountable for specific terminology learned (autotrophs, etc.)  and to apply the consequences of metal poisoning to what they've learned from the video to their model and verbal explanations. 

Standards Covered:

SP1- Asking questions (for science) and defining problems (for engineering).

SP2- Developing and Using Models.

SP4- Analyzing and interpreting data

MS-LS1-3-Use argument supported by evidence for how the body is a system of interacting subsystems composed of groups of cells. 

MS-LS2-3-Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem.

Explain

20 minutes

Section Sequence:

a) Slide 3: Share with students that since they now have a descent understanding of how heavy metals cycle and accumulate in human systems to create CNS problems, that they will further gain a deeper understanding of what occurs on the cellular and molecular levels of these impacted cells. 

b) Present and explain the chart on the slide. Instruct students to read the list of impacts and for each impact and in the second column produce an intricate image that reflects the general statement as it would appear in a nerve cell (students can use any example to express the words visually). In the third column, indicate the probable consequence of each problem brought about by mercury poisoning. An example includes: if the protein inhibited is an enzyme that catalyzes the production of a specific neurotransmitter such as serotonin, then inhibitory actions of the organism will be compromised. Students  should record their work in their lab book. 

 c) To jump start students on completing the chart, play the following video and fill in the first line with them on the board:

                           

Standards Covered:

SP2- Developing and Using Models.

MS-LS1-3-Use argument supported by evidence for how the body is a system of interacting subsystems composed of groups of cells. 

Extend

10 minutes

Section Sequence:

a) Present students with the following image Mercury Damage Versus Alzheimers and instruct them to observe the differences and similarities in Alzheimer's Patients versus those who suffer mercury toxicity.

b) Slide 4: Read the question prompt to the class and instruct them to complete the writing tasks as outlined in the WRITE part of the slide. 

c) Complete the DISCUSS section of the slide as a class. Draw parallels to the responses articulated and clarify any misconceptions using the image in step a. 

Standards Covered:

SP1- Asking questions (for science) and defining problems (for engineering).

SP2- Developing and Using Models.

SP4- Analyzing and interpreting data.

Evaluate

5 minutes

Section Sequence:

a) Slide 5: Provide students with index cards and instruct for them to place their names on and complete the task on the slide. Specify that they should think of some of the terminology reflected throughout the exercises performed. If needed, students can produce 2 word statements to articulate what they've learned.

Standards:

MS-LS1-3-Use argument supported by evidence for how the body is a system of interacting subsystems composed of groups of cells. 

MS-LS2-3-Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem.