Lights, Camera and Action Mechanisms of Neurotransmitters

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Objective

Students will interpret neurotransmitter data to deduce how one neuron influences the action of another.

Big Idea

Neurotransmitters have the potential to exude inhibitory or excitatory actions on neurons which control the traffic of signals in the brain's roadways.

Introduction

Lesson Background & Justification:

    Neurotransmitters are endogenous chemicals that transmit signals across a synapse from one neuron to another or target neuron. Once released from the presynaptic neuron, these chemicals can confer an excitatory or inhibitory effect on neurons by executing 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. The overall goal is to provide both up and down regulatory activity within the nervous system. In this lesson, students become familiarized with the action mechanisms of six common neurotransmitters and learn to classify them based on their unique abilities. 

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) Teacher preparation instructions for extension lab. See Extension Lab Instructions.

b) Student lab books.

c) Class set of Neurotransmitter Actions and Neurons in Series worksheets. (1 per student) 

d) Virtual Neuron Lab from DNALC.

Common Core and NGSS Standards:

HS-LS1-3-Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.

SP4- Analyzing and interpreting data. 

XC-P-LE-1. Patterns in the natural and human designed world can be observed, used to describe phenomena, and used as evidence.

Standards Rationale:

       In the science classroom, students are regularly charged with tasks to collect and make sense of data from readings and investigations. What makes these science experiences powerful enough to retain however, is an instructor's ability to access, stimulate and develop students' higher order thinking capacities for cognitive growth and subsequently establishing sound learning practices. In this lesson, students access, analyze & interpret scientific data and construct an argument for their personal positions on the topic of intelligence and gender. They utilize higher level Blooms thinking skills and modeling exercises which in tandem serve to intimately connect students to the tangibles and intangibles throughout the lesson. This promotes higher engagement and time on task as students absorb the content at hand.  

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 (a mechanical response), as a result gained momentum, propagates down the axon and finishes with the release of neurotransmitters (a chemical response) stored in vesicles at the end of the axon. This ultimately and consequently stimulates the post synaptic cell and repeats the process so that a message may transmitted from short and long distances within the body. To quantify said activity, an oscilloscope can be used to give us data for a better understanding of neurotransmitter activity.An oscilloscope, is a type of electronic test instrument that allows observation of constantly varying signal voltages or action potentials in many organisms from the venus fly trap to humans. In this section of the lesson, students gain an understanding of how this tool is utilized to give us insight on neurotransmitter activity. 

Section Sequence:

           In this section of the lesson, my goal is to develop students appreciation for scientific tools that measure activity that can not be readily visualized. The idea is to expose them to an discrepant experience that shows the versatility of the oscilloscope's capacity as it relates to neuroscience studies. This activity proceeds as follows:

a) Slide 1: Pose the challenge written on the screen and verbally collect students responses. Ask if not brought about: Does anyone know the neuroscience connection between this plant and you? Discuss. Share that we will view a clip to give us a little more insight & play the following:

b) Post video clip re-ask: "Does anyone know the neuroscience connection between this plant and you? Discuss until action potential or the ions need to propagate it are mentioned. Introduce the differences between a mechanical and chemical response to the students verbally and ask for them to modify their responses with the integration of these terms. 

c) Introduce the Oscilloscope Image to the class. Prompt students to infer how it works and then ask how they think this tool (the oscilloscope) impacts our understanding of the action potential similarities between humans and the venus fly trap. Finally, ask what are the tool's limitations in human neurotransmission. Discuss until someone mentions the activity of the neurotransmitters.  (Use leading questions that help for students to develop responses that lead to mentioning the identification of neurotransmitters)

Standards Covered:

SP4- Analyzing and interpreting data. 

XC-P-LE-1. Patterns in the natural and human designed world can be observed, used to describe phenomena, and used as evidence. 

Explore

20 minutes

Section Primer:

                GABA is an inhibitory neurotransmitter that is widely distributed in the neurons of the cortex. GABA contributes to motor control, vision, and many other cortical functions.  Glutamate is a major excitatory neurotransmitter that is associated with learning and memory. Neurons that use GABA and glutamate as neurotransmitters are used by more than 80% of the neurons in the brain and constitute the most important inhibition and excitation systems, respectively. It was long thought that a given neuron released only one kind of neurotransmitter. But today, many experiments show that a single neuron can produce several different neurotransmitters. In this section of the lesson, students learn how to discern the differences between the two major post-synaptic actions/outcomes of the receiving neuron.

 Section Sequence: 

a) Slide 2: Ask: "If the venus flytrap doesn't require neurotransmitters to perform this life functions, then what is the neurotranmitter's significance in the human body? Discuss until students mention that the neurons have synpases and that these chemicals are needed to jump start stimulation of the next neuron and continue the message over great distances (learned in Neuron Structure and Function Unit) This is not required of the plant and therefore, chemical signals that propagate electrochemical signals are not needed in the plant. Continue the discussion but fold in the stimulating activity that occurs once the post-synaptic neuron receives the chemical message. 

Note: Students can be stimulated to recall information to address the questions ask by asking leading questions such as: Does distance of the impulse make a difference? When are chemical signals needed most, over short distances? Or longer distances in the organism? 

b) Ask: As we have witnessed a diversity of these transmitters in the previous lesson, why is such a diverse group of chemicals needed to essentially generate the same affect on the receiving cell? In other words, what is the payoff for such diversity? Discuss until students articulate that the chemicals generate different behavioral responses depending on where it is produced in the brain. 

c) Slide 3: Share with students that we are going to explore one of the major benefits of neurotransmitter diversity by taking on two challenges. Organize students into partner pairs and give each student a copy of the activity Neurotransmitter Actions. Instruct students to record the first challenge question from the board (in red) in their lab books, perform the task (using the separate handout), and then return to their books to address the challenge question using data collected from the separate worksheet.

d) Instruct students to complete the second challenge using the activity Neurons in Series and to record the answer to the second challenge question (in blue) in their lab books. 

e) Discuss student discoveries. Be certain that students are clear on what it means to be an inhibitory molecule versus excitatory. 

Standards Covered: 

HS-LS1-3-Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.

SP4- Analyzing and interpreting data. 

XC-P-LE-1. Patterns in the natural and human designed world can be observed, used to describe phenomena, and used as evidence.

Explain

15 minutes

Section Primer:

         There are two major kinds of action classes of neurotransmitters: Inhibitory and Excitatory. Excitatory neurotransmitters are what stimulate the brain.  Those that calm the brain and help create balance are called inhibitory.  Inhibitory neurotransmitters balance mood and are easily depleted when the excitatory neurotransmitters are overactive. Together, they maintain a checks and balance system to ascertain full functional capacity of the nervous system. In this section of the lesson, students revisit and review the benefits of this system and learn to classify six neurotransmitters based on their post-synaptic action effects. 

Section Sequence: 

a) Slide 2: Direct students attention to the chart at the bottom of the screen. Share that our objective of this unit is to understand how 6 of the 100 different discovered neurotransmitter compare and contrast. Ask students to recall and record in their books the list of the six molecules that they worked with in the previous lesson and list them in the first column on the board.

b) Ask students to hypothesize the action mechanism of each based on what they have learned about each from the previous day. Hypothesize and record I for Inhibitory and E for Excitatory in the second column. Finally project each neurotransmitter sheet from lesson 1 up one by one on the screen, read aloud as a class and fill in the remaining column based on the stated information.

c) To reinforce and expand students understanding of how these neurotransmitters impact the actions of neurons that they make contact with, proceed to the following slides and address their corresponding points of discussion: 

Slide 3: Instruct students to articulate the differences between I and E actions as it relates   to cell polarity and the chemical consequences (ion influx, etc.) of each. 

Slide 4: Instruct students to articulate whether or not if excitability and/or inhibition implies a standard level of neuron activity. Direct them to the graph to justify their responses. 

Slide 5: Instruct students to consider that the pie graph represents the type and relative quantity of neurotransmitters produced in a specific region of the brain. Discuss the implications of the data. For instance, does it have a checks and balance system?, Is it mostly E or I?, and so on. 

Extend

30 minutes

Section Sequence: 

       In this section of the lesson, students utilize a variety of clues (in the form of a wet lab simulation and recorded information) to help them identify each of the six neurotransmitter discussed thus far. This activity proceeds as follows:

a) Slide 6: Share with students that we are now going to see how well they are able to identify the six major neurotransmitters based on two properties alone: 1)their chemical responses or luminescence abilties (as a result of electrical activity) and 2) descriptions of their functions.

b) Proceed to explain the directions to the students as it appears on the board and allow for them to execute the activities according to the information on the screen as well as specific instructions within the Extension Lab Instructions (attached). (See Extension Pics 1-3 to observe student work and execution. Picture 1 shows the luminescence experienced by the "cultured neurons" during the lab)

Standards Covered:

HS-LS1-3-Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.

SP4- Analyzing and interpreting data. 

XC-P-LE-1. Patterns in the natural and human designed world can be observed, used to describe phenomena, and used as evidence.

Evaluate

15 minutes

Section Sequence:

     In this section of the lesson, the objective is to have students apply their knowledge neurotransmitter actions to various tiers of neuron circuitry. This comes in the form of five virtual challenges and students can complete this as a class (with an appointed student to execute commands from the class) or in smaller groups if the technology is available to accommodate these groups. This activity proceeds as follows:

a) Slide 7: Read and explain the goal of the evaluation activity as it appears on the screen. Share with students that this virtual activity will help to assess what they understand about several neurotransmitter actions in different scenarios.  

b) Instruct students to submit their explanations at the conclusion of class and grade based on how well they communicate the significance of the synergy between both the I and E type of chemicals. 

Standards Covered:

SP2- Developing and using models.

SP4- Analyzing and interpreting data. 

XC-P-LE-1. Patterns in the natural and human designed world can be observed, used to describe phenomena, and used as evidence.