Strategies and Lesson Plans
The goal for this unit is to not only give students an understanding of the nervous system, but to also connect them to the kinds of research being done in universities they might be attending, and prepare them to participate in that research. In order for them to be ready, they must have an understanding of what it takes to design and conduct an investigation. During this unit students will read about research, "dissect" the research, replicate the research, and design their own investigation related to research in neurobiology. If you cannot access the journal articles used in this unit, find others that will be of interest to your students and prepare "dissection" guides for them.
Day 1—The unit will begin with a lecture on the structure of a neuron. Neurons are cells, and I will have students review cells by asking them to describe how this type of cell might be like the generic cell they diagrammed in IB Biology II. What organelles might it need and why? Where would organelles be found in a neuron? The lesson will continue with a lecture on the propagation of an action potential. To help students understand that the action potential does not involve movement of molecules down the axon, we will act out an action potential by doing "The Action Potential Wave". (See Activity 1)
Day 2— Students will review membrane structure and transport and relate it to the previous day's lecture on the action potential. In order for them to get a feel for how scientists might have studied the changes in membrane potential in a neuron, students will use conductivity probe-ware to measure the flow of ions as salt water diffuses through dialysis tubing. A good description of this type of lab can be found at http://cms.upb.pitt.edu/uploadedFiles/About/Sponsored_Programs/Science_In_Motion/Biology_Labs/bio019_%20Vernier%20-%20Diffusion%20Through%20Membranes.doc. After a lecture on synaptic transmission, students will investigate the effects of the drugs cocaine, amphetamines, benzodiazepines, nicotine, cannabis, THC, and alcohol on synaptic transmission and make short reports to the class on the effects of the drug they researched.
Day 3—Having looked at the smallest unit in the nervous system, students will be given a short introduction about the evolution of the brain. After going over the parts of the brain and their functions, students will be given pictures of various vertebrate brains and told to match them to the animal they came from based on what they know about phylogeny and the characteristics of the animals and what parts of the brain the animal might use most. Students will then make a three-dimensional model of the human brain from a series of MRI images, labeling all important areas, and providing an annotated key with their model. (See Activity 2) For homework, students will read a Scientific American article, "Origins of the Left & Right Brain", and answer questions from a reading guide in preparation for dissecting and replicating an experiment described in the article. (See Activity 3)
Day 4—The article, "Origins of the Left & Right Brain" describes the evidence collected for the evolution of lateralization of the brain in vertebrate animals. Several behavioral studies are described in the article. Having read about them the previous night, I will give the students a copy of the one of the original reports—"Complementary right and left hemifield use for predatory and agonistic behavior in toads" by G. Vallortigara, L.J. Rogers, and others—along with "Dissection Instructions". (See Activity 4) There are a few vocabulary words in the report that students might not be familiar with, and we will go over these in class, trying to define them using context. Students will then work with lab partners to "dissect" the report and discover how the experiment was designed to control for variables, to test for the hypothesis, and to collect sufficient data.
Day 5—Students will replicate the predatory behavior experiment with toads described in the Vallortigara paper. The experiment involves presenting prey—worms or crickets—to toads from a clockwise or counter-clockwise direction and recording the point where the toad strikes at the prey. Having read, and thoroughly worked through the steps of the experiment, they should have a good idea about why they are doing what they are doing, and what outcome they should expect. Safety and animal care procedures must be reviewed before beginning the lab. We will discuss any deviations we will have to make from the methods described in the report due to budgetary, time, and equipment constraints, and come up with the methods for collecting data that each lab group will use. However, they will be working with live toads. I will have students do a test run of our procedures and make adjustments before going any further. We will discuss whether the adjustments might make a difference in the validity of our results. The toads will be kept in the classroom following the experiment.
Day 6—(Possible second day of the toad experiment) Following the collection and analysis of class data from the experiment, students will compare their results to the results reported in the original report, and discuss possible sources of error and ways to improve the procedure for classroom use.
Day 7—A power point presentation on various imaging techniques used to study the brain will be presented to the students, using several disorders as the focus of those images—schizophrenia, Parkinson's disease, and Alzheimer's disease. Students will then be given a summary of a study done at UNC on the effects of a cell membrane receptor protein—NCAM—involved in helping neurons in the pre-frontal cortex form synapses. Individuals with schizophrenia have unusually high levels of fragments of this protein in the brain. Transgenic mice, with a gene that creates similarly high levels of NCAM fragments, are being used to study the effects of these fragments on synapse development. 32 Because the article is very technical, I have summarized it for the students, leaving in the essential information on the methodology used. One of the authors provided me with images of neurons and brain tissue from the wild and knockout mice for my students to look at and compare. Students will identify and count the number of neurons on each slide, count the number of processes from each neuron and the number of branches, and come up with a branching index for each slide. They will then compare their results with the results reported in the article. For access to this activity, see Teacher Resources.
Day 8—A behavior study was also done with the mice in conjunction with the brain tissue analysis. Wild and knockout mice were made to swim in a T-maze to test the decision making ability of their pre-frontal cortex. Students will be given a description of the experiment to dissect, and data from the experiment to analyze.
Day 9 and 10—Students will draw and label a diagram of the human eye, dissect a sheep eye and compare the structures in the two. Following a lecture on how vision occurs from the retina to the vision centers in the brain, students will explore a variety of visual tests and optical illusions. They will then be given an assignment to research the sensory organs and behavior of either crickets, mealworms, or earthworms.
Day 11-12—As a culminating activity, each students will design a lab testing or investigating the senses of the animal they have selected to research. They will be expected to incorporate all they have learned about good experimental design, conduct their experiment, analyze the results, and make a presentation to the class.
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