The Highs and Lows of Serotonin's Neurotransmission!

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Objective

Students will collect and interpret data from a simulation to explain the homeostatic activity of Serotonin in the human brain.

Big Idea

Serotonin serves as the brake system of the brain. Left unchecked, humans can be potentially susceptible to a host of negative behavioral responses.

Introduction

Lesson Background & Justification:

    Neurotransmitters are endogenous chemicals that transmit signals across a synapse from one neuron to another or target neuron. Serotonin is a neurotransmitter and chemical created by the gut of the human body that works as a neurotransmitter and intestinal regulator. In the brain, it is regarded by some researchers as a chemical that is responsible for maintaining mood balance, and that a deficit of serotonin leads to depression. Once synthesized from tryptophan and stored in vesicles, it is released from the presynaptic neuron and 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 inhibitory response of its receiving cell. In this lesson, students become familiarized with the standard neurotransmission activities of the serotonin circuit and learn to interpret data that implicates its this neurotransmitter in the addiction equation alongside another neurotransmitter dopamine, an excitatory chemical. 

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 Life Science Learning Center's Lab: Long Term Effects of Drug Addiction Print out and Materials (1 lab per student pair) Teacher Instructions  &  Student Print Outs 

b) Student lab books.

c) Class set of Serotonin note sheets, Brain Outline half sheets and Mind Map sheets (1 per student). 

Common Core and NGSS Standards:

SP4- Analyzing and interpreting data.

SP2- Developing and Using Models.

WHST.11-12.2.d- Use precise language, domain-specific vocabulary and techniques such as metaphor, simile, and analogy to manage the complexity of the topic; convey a knowledgeable stance in a style that responds to the discipline and context as well as to the expertise of likely readers.

HS-LS1-1- Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.

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 instructional practices such building analogies to promote students’ reasoning and understanding of the core science idea presented (mechanisms of maintaining homeostasis of the nervous via Serotonin transmission and activity).

Engage

5 minutes

Section Primer: 

         Addiction is a primary, chronic disease of brain reward, motivation, memory and related circuitry. It is characterized by inability to consistently abstain, impairment in behavioral control, craving, diminished recognition of significant problems with one’s behaviors and interpersonal relationships, and a dysfunctional emotional response to a number of items including drugs, food and relationships. In this section of the of the lesson, students minds are opened to an unconventional addiction habit of chronic rock noshing. The idea is to prompt them to think about how we should define addiction and opens the stage for them to internalize the similarities between persons being addicted to drugs versus unconventional & dangerous food preferences.

Section Sequence:

a) Ask students if they have any unconventional habits or perhaps addictions and request for them to share with the group if their comfort level permits. Once sharing is exhausted, ask why they think that people continue to  perform such behaviors, even if they may not contribute to their well being (as most behaviors are a function of survival). Discuss. Then inform students that they will look at another extreme example and to listen for anything that may help them to explain why this person feels compelled to continue with such unhealthy behaviors. Discuss responses post video until an understanding is reached that these behaviors almost seem involuntary because they are responding to an strong internal desire.

Note: You may want to encourage students to consider or arrive at the idea of something being wrong in the brain’s circuitry/functioning. 

b) Say: "Neuroscientists have discovered that no matter the action, be it rock noshing, or (list some examples from the student responses), obsessions, or even drug addictions that the brain and body utilizes three neurotransmitters to drive these perceived needs. They, together are the perfect equation for addictive behaviors. Today, we are going to figure out how they link together in this equation and will be able to by the end of the lesson fill in and explain the math symbols replaced by question marks seen on the screen." 

Explore

20 minutes

Section Primer: 

      mind map is a diagram used to visually organize information. It is often created around a single concept, drawn as an image in the center of a blank landscape page, to which associated representations of ideas such as images, words and parts of words are added. Major ideas are connected directly to the central concept, and other ideas branch out from those. In this section of the lesson, students will, via video presentation and mind mapping learn to explain how serotonin, endorphins and dopamine work synergistically in the addiction equation. 

Section Sequence: 

a) Slide 2: Distribute the mind mapping illustration sheet* to each student and share that they will learn how these three neurotransmitters work in the addiction equation by building a mind map of addiction using the images and words on the sheet in addition to their own. Explain the concept of a mind map using the image projected. Finally, share that they will use information from an explanatory video and discussion to develop their maps. 

*Alternatively, students can be given the sheet (full of terms and illustrations) for homework to cut out the items that they will use to build their maps in the effort to save time in class. 

b) Play the following video, and stop at the following times to give students time to add images and information to their mind map and to discuss the corresponding questions below:

0:00 Preface with instructing students to draw an image that they associate with addiction in the center of a page in their lab book. Ask, why did we record addiction here? Discuss.

2:56 Share that stress and feelings of anxiety are feelings that people experience during their addictive cravings to put the initial part of the film into perspective. Give students a few minutes to update their maps based on the information presented to this point. 

3:12 Have students verbally predict which neurotransmitter of the ones initially listed serves the role of keeping dopamine in check. 

3:33 Ask:Why do you think people describe their agent of addiction as a need? Discuss & update.

5:18 Update maps.

6:06 Ask:What is chemical differences between a normal person and an addict? Discuss. Update.

7:00 Stop and wrap up mind maps by briefly giving their partners an overview of their thinking and/or patterns. Inform students that any remaining images will be used later as they learn more about serotonin and addiction. 

Standards Covered:

SP2- Developing and Using Models.

WHST.11-12.2.d- Use precise language, domain-specific vocabulary and techniques such as metaphor, simile, and analogy to manage the complexity of the topic; convey a knowledgeable stance in a style that responds to the discipline and context as well as to the expertise of likely readers.

Explain

10 minutes

Section Primer: 

        There are two kinds of neurotransmitters: Inhibitory and ExcitatoryExcitatory Nt's stimulate the brain as a result of a depolarizing event which induces the influx of sodium ions into the neuron, which generates an action potential. Conversely, when an inhibitory Nt like serotonin activates the receptor site, it causes additional potassium channels to open which causes potassium ions to flow out of the cell and makes the inside of the cell more negative. Consequently, this prevents an action potential from propagating even in the face of an excitatory Nt like dopamine. In this section of the lesson, students learn to compare and contrast the post synaptic events of INt's and ENt's and it's consequences in the brain and in the addiction equation. 

Section Sequence:

a) Slide 3: Distribute the Serotonin Note sheet to all students. Share that they will learn a little more about the inhibitory Nt serotonin and that they will use their half sheets as template to take notes on its neurotransmission process and use this information to build their mind maps more.  

b) Start by instructing students to color each box on their diagrams differently. Tell them that they will build their legend for the diagram as we describe the events on the corresponding image on the screen. Finally, use the diagrams on the screen to explain how serotonin is synthesized in the cell body, processed at the synapse and interpreted by the post-synaptic neuron. Emphasize how this prevents the excitatory Nt dopamine for acting on neurons. 

c) Discuss why low serotonin levels leads to addicting behaviors as in the rock example earlier. (This leaves no check system for dopamine which drives demanding behaviors to fulfill a "need")

d) Slide 4: Read and direct students to complete the outlined task projected. (See student work attached to clarify student activity)

e) Instruct students to update their mind maps to include new information.

Standards Covered:

WHST.11-12.2.d- Use precise language, domain-specific vocabulary and techniques such as metaphor, simile, and analogy to manage the complexity of the topic; convey a knowledgeable stance in a style that responds to the discipline and context as well as to the expertise of likely readers.

 

Extend

45 minutes

Section Primer:

      A DNA Microarray is a collection of microscopic DNA spots attached to a solid surface. Scientists use DNA microarrays to measure the expression levels of large numbers of genes simultaneously or to genotype multiple regions of a genome. This in addition to PET scans have used in neuroscience labs to make the genetic connections between drug addiction and changes in the brain's landscape. In this section of the lesson, students explore a simulation lab which helps them to build an understanding of how the brain changes when one has an addiction problem. 

Section Sequence: 

a) Slide 5: Read and direct students through the list of tasks projected. Students will complete tasks within the  Long Term Effects of Drug Addiction Activity:  Teacher Instructions  &  Student Print Outs 

Note: To minimize working space issues, direct students to glue or tape their notes from the explain section in their lab books and to stack their mind maps in the center of the table before they obtain their materials for the extension lab. 

Standards Covered:

SP4- Analyzing and interpreting data.

SP2- Developing and Using Models.

WHST.11-12.2.d- Use precise language, domain-specific vocabulary and techniques such as metaphor, simile, and analogy to manage the complexity of the topic; convey a knowledgeable stance in a style that responds to the discipline and context as well as to the expertise of likely readers.

HS-LS1-1- Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells 

Evaluate

10 minutes

Section Sequence: 

a) Slide 6: Share with students that they will revisit and complete the initial addiction equation and use the information from their mind maps to develop an analogy for serotonin's normal role in the body or/and its role in the addiction equation. Read and direct students to complete the prescribed evaluation tasks seen on the screen. 

Standards Covered:

SP2- Developing and Using Models.

WHST.11-12.2.d- Use precise language, domain-specific vocabulary and techniques such as metaphor, simile, and analogy to manage the complexity of the topic; convey a knowledgeable stance in a style that responds to the discipline and context as well as to the expertise of likely readers.