Of Love and Addiction: Understanding Dopamine's Physiological Impact!

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Objective

Students will interpret data from an addiction model to explain how dopamine functions in the human brain.

Big Idea

Dopamine is the "rewarding" agent of the brain that can lead to both repetitive positive and negative behaviors.

Introduction

Lesson Background & Justification:

    Neurotransmitters are endogenous chemicals that transmit signals across a synapse from one neuron to another or target neuron. Dopamine is a neurotransmitter that helps control the brain's reward and pleasure centers to provide a premium for reward seeking behaviors in humans like sex and eating foods in addition to providing stimulation in other brain systems. 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 this lesson, students become familiarized with the standard neurotransmission activities of the dopamine circuit and learn to interpret data that implicates its this neurotransmitter in the addiction equation. 

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 Science Take Out's Brain Reward Pathway and Addiction Lab. (1 lab per student pair) 

b) Student lab books.

c) Class set of Understanding How Dopamine Works note sheets and Brain Outine half sheets (1 per student) 

Common Core and NGSS Standards:

SP4- Analyzing and interpreting data.

SP2- Developing and Using Models.

XC-P-UE-3-Patterns can be used as evidence to support an explanation.

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 Dopamine transmission and activity).

Engage

10 minutes

Section Primer: 

        Heroin is a highly addictive analgesic drug derived from morphine, often used illicitly as a narcotic producing euphoria by hijacking the Dopamine reward pathways of the brain. In this section of the lesson students are introduced to the rewarding affects of dopamine through comparing and contrasting the implications of dopamine presence in a movie trailer focused on the emotional euphoria experienced through love and a news brief focused on the physical euphoria associated with using heroin. The goal is to motivate students to open their minds to the molecular activity evoked by dopamine in the human brain which they will learn in subsequent sections. 

Section Sequence:

a) Slide 1: Ask:"When you hear the word dopamine, what effect would you believe that it has on the brain based on name alone?" Allow students to share out and to explain why they thought of the articulated adjectives and/or impacts. 

b) Share that much like the variety of responses produced, dopamine stimulates a variety of behaviors in humans. Tell students that they will view two clips that eludes to the behaviors manifested from dopamine in the brain & that they are to share what the clips suggest post clip. 

c)Play the following and discuss thereafter.  

 d) Play the following and discuss thereafter.   

e) Initiate a discussion to compare and contrast the behaviors seen in the videos. Finally, share that we will learn more about how this molecule can generate very different behaviors. 

Standards Covered:

XC-P-UE-3-Patterns can be used as evidence to support an explanation.

Explore

30 minutes

Section Primer: 

        The brain is divided into several distinct regions that are each responsible for performing different functions. In the center of the brain sits the Reward Pathway, which is responsible for driving our feelings of motivation, reward and behavior. Such behaviors include positive ones such as consuming tasty foods and negative such as developing dependency on a chemical stimulus or addiction. In this section of the lesson, students via a simulated addiction study explore the connection between the brain reward pathway system, dopamine and addiction. 

Section Sequence:

Slide 2: Read and direct students to complete the tasks associated with the addiction lab. Discuss students trends and what those trends suggest about connections between the brain reward pathway system, dopamine and addiction.

For Fun: After we as a class completed the exploration activity and discussed the results, we added arbitrary data to our graphs based on personal experiences. To gauge students level of understanding of the relationship between the quantity of dopamine, time and stimulants, I instructed them to add predicted values of dopamine levels & time on their graphs in response to the following stimulants:

a) Being in the presence of someone that they were "in love with" or had strong emotions for.

b) April's experience with injecting heroin into her system (the case study in the engage video).

See student graphs for their predicted results! 

Standards Covered: 

SP4- Analyzing and interpreting data.

SP2- Developing and Using Models.

XC-P-UE-3-Patterns can be used as evidence to support an explanation.

Explain

20 minutes

Section Primer:

      A protein-coupled receptor (GPCR), also called seven-transmembrane receptor or  heptahelical receptor, is a protein located in the cell membrane that binds to extracellular substances such as neurotransmitters and transmits signals from these substances to an intra- cellular molecule called a G protein or guanine nucleotide-binding protein. Once bound, a specific neurotransmitter such as dopamine triggers a conformational change of the protein which subsequently triggers downstream factors that ultimately initiate an action potential in the post- synaptic neuron. In this section of the lesson, students learn to describe this activity as a part of the dopamine neurotransmission process and compare and contrast it to the initiation of a direct ion channel in other systems such as the acetylcholine system.  

Section Sequence:

a) Slide 3: Distribute the guided note sheet: Understanding How Dopamine Works to each students. Share that they will watch a series of videos to explain the synthesis and general synaptic transmission of dopamine, and how it it employs a unique protein in its neurotransmission system called GPCR. Review the layout of their note sheets and inform them that they will update/layer their sheets with content as it is present in the videos and discussed by the class. 

b) Play the following video, but stop it at 1:18. Discuss unveiled content and illustrate this on the screen. (The goal of this video is to visually articulate the the neurotransmission cycle of dopamine at the synapse level.)

c) Repeat step b, with the following video. However preface by showing students where the video starts on the diagram projected (G-Protein Coupled Receptor on the post synaptic neuron). (The goal of this 2nd tier/layer video is demonstrate and explain the specific biochemical changes and processes experienced by the dopamine receptors once they interface with the Nt.)

 d) Repeat step b with the following video, but stop at 54 seconds. (The goal of this video is to visually articulate how dopamine is reabsorbed and treated post release and synapse level activity.)

e) Complete an overview of the dopamine neurotransmission system by filling in the illustration on the screen. 

f) Slide 4: Use the diagram on this slide to compare and contrast how the protein receptors of the receiving cells differ in structure and function with the dopamine system to the left and the acetylcholine system to the right. Stress that both evoke excitatory actions within the neuron but vary in timing. Direct students to the structures of each (ask questions such as how many constituents of the receptor system are present and how might this impact processing time to focus and move students along) Ask: Might it take longer for you to contract a muscle or to feel the effect of drug? Are there advantages to the differences in timing? Discuss. 

Note: The goal is to show students the significance of specialized structures and functions in the nervous system, particularly in excitatory systems such as those that employ dopamine. 

Extend

20 minutes

Section Sequence: 

       In this section of the lesson, the goal is to demonstrate to students how to quantify behavioral responses of addiction and thus, dopamine chemical influence on the brain. This data is then used to guide a class discussion on the molecular events within the brain reward system of the organism that is exhibiting addictive behaviors. 

a) Slide: Read the instructions projected and guide students through the set of tasks. After step 4, help students to develop and articulate responses that not only state the behavioral trends but include a molecular explanation (dopamine pathways and neurotransmission) for each variation in the graph.  

Standards Covered:

SP4- Analyzing and interpreting data.

SP2- Developing and Using Models.

XC-P-UE-3-Patterns can be used as evidence to support an explanation.

Evaluate

10 minutes

Section Sequence:

    In this section of the lesson, students apply their content to interpret a graph from an addiction study. The goal is to see if students can generate correlations between data and biological events. This activity proceeds as follows:

a) Slide 6: Instruct students to observe the graph on the screen and produce information that reasonably articulates what the designated (yellow boxes) areas on the graph should convey. Share that their explanations/terms should include molecular activity or vocabulary in or from the dopamine system studied today. 

Note: Students should provide answers similar to the following:

a) X axis= activity level of rat

b) Y axis= level of dopamine

c) other boxes= degree of response 

Standards Covered:

SP4- Analyzing and interpreting data.

XC-P-UE-3-Patterns can be used as evidence to support an explanation.