This investigative case module was prepared as part of a BioQUEST faculty development workshop entitled NSF Chautauqua Short Course: Investigative Cases at Christian Brothers University in July 2004. The cases, resources, and implementation strategies were developed by participants for use with their own students. We invite you to adopt and adapt the following materials.

The BioQUEST Curriculum Consortium is committed to the reform of undergraduate biology instruction through an emphasis on engaging students in realistic scientific practices. This approach is sometimes characterized as an inquiry driven approach and is captured in BioQUEST's three P's (problem-posing, problem-solving, and peer-persuasion). As part of this workshop groups of faculty were encouraged to initiate innovative curricular projects. We are sharing these works in progress in the hope that they will stimulate further exploration, collaboration and development. Please see the following links for additional information:

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Investigative Cases
   
The Case: Low Calcium Tetany

Part 1:
Lori notices that David keeps nodding off during Dr. Whaley’s lecture. At the break she begins to tease him about having a late night. “What did you do last night?" Lori asked, "... a hot date?”

“I wish,” replied David. "I woke up at three in the morning with a bad leg cramp. I jumped out of bed and yelled so much I woke up my roommate. And it's the second time this week.”


Colin listened to David’s story and responded, "When that happened to me my mom told me to drink more milk.”

Other students begin to give David advice and agree that he needs to eat more bananas.

David wonders, “Can something I eat really relieve my leg cramps?”

Part 2:

After doing a Google search on muscle cramps, David learns that deficiencies of calcium and potassium can both cause leg cramps. He also reads in his text book that the voltage-gated sodium channels in neurons require calcium for their complete closure.

"So," he thinks, "How do low levels of calcium and potassium cause my muscles to cramp?"

Case Author:
Brenda Whaley Houston Baptist University

Case Analysis

Part 1
WHAT WE KNOW:

Muscle cramps are an uncontrolled muscle contraction.
Muscle contractions are generated by an action potential in a somatic motor neuron.
Action potentials are generated when sodium enters the neuron through voltage-gated sodium channels.
An action potential is normally followed by a return to the resting potential.

WHAT WE NEED TO KNOW

What would cause an undesired action potential to be generated in a somatic motor neuron?
Is there something in milk that can affect the generation of an action potential?
Is there something in bananas that can affect the generation of an action potential?

Part 2

WHAT WE KNOW:

Calcium is needed for the normal function of voltage-gated sodium channels.
Milk is good source of calcium.
Potassium is pumped into the cell by the sodium-potassium pump during the generation of a resting potential.

WHAT WE NEED TO KNOW

Do bananas contain high levels of one of the ions that are important to normal neuron function?
How would low levels of calcium affect the function of a neuron?
How would low levels of potassium affect the function of a neuron?

Option: Include a know / need to know chart like the one below:

What do you know?
What do you need to know?
   

Learning Goals

Goal(s)

In evaluating how low levels of calcium would alter the function of neurons students will reinforce their understanding of the function of voltage-gated sodium channels in the initiation of the action potential.
In evaluating how low levels of potassium would alter the function of neurons students will reinforce their understanding of the function this ion plays in the generation of the resting potential.
In investigating the variety of disease states that can lead to low electrolyte levels students will better understand the complexities involved in homeostasis.

Standards

 

Investigations and Activities

1. Students will be required to use their knowledge of the function of voltage-gated sodium channels to explain why low levels of calcium might induce leg cramps.
2. Students will be required to use their knowledge of the function of potassium in the generation of the resting potential to explain why low levels of calcium might induce leg cramps.
3. Students will be asked to identify and describe the pathology of three different disease states which are characterized by muscle cramps induced by low levels of either calcium or potassium.

 

Resources

1. The textbook.
2. Class lecture notes.
3. Internet access to health.discovery.com.

Students will usually obtain additional references or resources
to help answer or explore their questions.

Special Data Items

 

Student Products

Each students will be ask to turn in a completed worksheet that asks the following:

1. Explain on a molecular level how low levels of calcium might induce muscle cramps.
2. Explain on a molecular level how low levels of potassium might induce muscle cramps.
3. Identify three disease states that are characterized by muscle cramps induced by low levels of calcium (hypocalcemia) or low levels of potassium (hypoalkemia).
4. For each of the disease states you identified explain why calcium or potassium levels are less than normal homeostatic levels.

Assessment and Evaluation Plan

 

Implementation

The case study will be introduced at the end of the first course module covering muscle contraction and neural function.

Course name:
General Biology 3
Likely sequence in syllabus:
Following study of muscle contraction and neural action potential
Time during term:
Following first exam
Duration:
One week
Setting:
In class small group discussion and out of class internet searches.
Students in course:
First-year Biology Majors
Collaborative elements:
Students will fill out Know/Need to Know tables in small groups
Additional notes:

 

Credits

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