Of Cellular Transport and the Cerebrum! (Day 1)

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Objective

Students will be able develop and use models to simulate the causes of brain dehydration.

Big Idea

Brains require adequate hydration to perform to execute its regular functions!

Introduction

Lesson Background & Justification:

    Cell transport is the movement of materials across cell membranes. Cell transport can be performed via passive and active transport depending on whether the action does or does not require energy. Passive transport (eg. diffusion and osmosis) is an example of diffusion does not require energy whereas Active Transport (eg. ion transport) requires energy to proceed. Passive transport will be initially be explored in this first of a two part lesson sequence in the effort to scaffold the materials gradually and logically to comprehend how and why materials can be transported in and out the cell at varied frequencies.  

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 Kit: Cell Membranes: Diffusion and Osmosis (1 per student pair)

b) A class set of plasma membrane practice strips and glue sticks. 

c) Student lab books.

Common Core and NGSS Standards:

SP4- Analyzing and interpreting data.

SP2- Developing and Using Models.

HS-LS13: Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.

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).

Engage

5 minutes

Section Sequence:

          In this section of the lesson, my goal is to draw students interest into the impact of the over consumption of alcohol on the human brain. The idea is to introduce students to the concept of osmosis and then later provide them with tools to model the dehydration process of the neurons and cells in general. This activity proceeds as follows:

a) Ask: "What are some immediate problems that people encounter when they drink excessively?" Discuss. "What do you think the alcohol does to the brain? Body?" Discuss.

b) Slide 1: State "Due to its chemistry, alcohol is known to dehydrate the brain." Discuss the implications of the MRI results presented. Focus on brain structure and function. Draw students attention to the blue areas if they don't recognize these emphasized areas. Review the parts of the brain impacted (eg. cerebellum, brain stem, mid-brain, and occipital lobe), their respective functions (See previous Brain Anatomy Lesson) and the inferred consequences of their less than optimal hydration status. 

c) Ask rhetorically: "As important as our brains are, how do we lose water to alcohol?". Let's explore how water moves in and out of cells in general.

Standards Covered: 

SP4- Analyzing and interpreting data.   

Explore

60 minutes

Section Primer:

           Osmosis is the spontaneous net movement of water (solvent molecules) through a semipermeable membrane into a region of higher solute (ions, monomers, etc.) concentration, to an area of lower solute concentration. This natural mechanism is utilized in the body to equalize and stabilize water volumes to maintain the organism's homeostatic processes, including those required by the human brain. Unbalanced fluid levels in the human brain typically lead to problems with control over balance, thinking and responding to environmental stimuli.

Section Sequence: 

          In this section of the lesson, my goal is to give students an opportunity to discover how the process of osmosis works via a simulation. The idea is to build students' vocabulary & contextual understanding of osmosis & how it leads to the swelling and shrinking of materials in general so that they may explain its impact on the brain. This activity proceeds as follows:

a) Slide 2: State "This is a cross section and enhanced view of a specific area of our brains. Your objective will be to explain how materials move in between the areas illustrated on the image". Emphasize via pointing, the specific areas of movement between cells. 

b) Distribute Cell Membranes: Diffusion and Osmosis student kits & instruct them to complete section 1, part A. Review solute movement questions (page 7 #'s 11-14) with the class as a whole after 20 minutes. 

c) Restate the overall goal of the exploration activity and verbally instruct them to complete section 1, part B. Review the section's question responses (page 8 #'s 1-4) with the class after 5 minutes. 

d) Verbally instruct students to complete section C and review after 15 minutes. 

e) Remind students that we are using a model to explain how alcohol encourages water movement out of the brain before verbally instructing them to complete Part 2: Osmosis (1-4). After 5 minutes, discuss how diffusion and osmosis compare and contrast to one another. 

f) Instruct students to discuss the images that accompany Part 2, section A, using the instructions of the section only as guide to direct their discussions. Give students 5 minutes to complete and then discuss as a class. 

Standards Covered:

SP2- Developing and Using Models.

HS-LS13: Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis. 

Explain

25 minutes

Section Sequence:

          In this section of the lesson, my goal is to give students the opportunity to review, illustrate and articulate their understanding the cellular transport process of osmosis and diffusion. The idea is to empower students to use the knowledge acquired in their exploration activities to explain how alcohol moves in and out of brain cells and creates problems for those who consume it heavily. This activity proceeds as follows:

a) Slide 3: Instruct students to produce an outline of neuron as it appears on the screen inside of their lab books. 

b) Provide students with a plasma membrane practice strip and instruct them to glue it in their lab books close to their neuron outline to represent a zoom in section of the neuron's membrane as it appears on the slide. Instruct students to use the images to record a full explanation of osmosis and diffusion using the video as a guide or virtual instructor. Play the following video:     

       

c) Post video, clarify any questions that students may have about their notes. 

d) Return to section B of the Cell Membranes: Diffusion and Osmosis kits and discuss as a class. Finally, instruct students to use their note images to illustrate and summarize how and why alcohol shrinks the brain overall (see reflection for student examples)

Wrap up: Solicit volunteers to verbally summarize to the class how and why the processes of diffusion and osmosis influences changes in the brain when one consumes a great deal of drinking alcohol. Encourage the student audience to cross reference their illustrations to either add to the presentation or modify their models to reflect more accurate information.  

Standards Covered:

SP2- Developing and Using Models.