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Teaching Guide
Coordinated Control
Nuclear Transplants
Uncovering a Signal
Quiz
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As you learned in "Nerves of Steel" Functional electrical stimulation, or FES, for short is a technique that uses external electrical signals to stimulate muscle contraction. Electrodes are implanted into target muscle groups. When impulses are discharged into these sites, the muscles behave as if they had been stimulated by neurons.

In the past, scientists had hoped that FES might offer a bank of controlled movements to paraplegics. These days, however, the goals are more conservative. Through coordinated impulses, FES is aimed at elevating a person from a chair, allowing he or she to "stand and transfer". Although the action may not seem lofty, this simple movement opens an arena of independence for those restricted to wheelchairs.

In this activity, you'll observe how split second timing is essential to coordinated control. First, you'll assemble two electromagnet circuits. Then, you'll apply coordinated control to direct the roll direction of a steel bearing.

Note to educators

 

OBJECTIVE
This activity page will offer:

  • background in Functional Electric Stimulation
  • an opportunity to integrate physical science (circuit construction) with life science (coordination and technology application)
  • a hands-on experience in defining coordination

MATERIALS

  • bell wire
  • 2 button switches*
  • two iron nails
  • 2 "D" Batteries
  • steel bearing (1/4" or larger)
  • cardboard or scrap foam core
  • tape

* Any type of pressure switch or doorbell button will do.

SAFETY: Review all safety procedures associated with heat generated by this type of electromagnetic circuit. Remind students to keep the circuit closed for ONLY short periods of time. With the current flowing, the wire will heat to temperatures that can cause burns.

 


PROCEDURE

PART 1 - Building the Coordinated Clip Fall

  1. Work in teams of two. Examine both the schematic drawing and the set-up illustration.
  2. Gather the materials needed to assemble the two electromagnetic circuits and the support board.
  3. With your instructor's approval and guidance, assemble the wiring and platform. Wrapping insulated bell wire around an iron nail forms each of the two electromagnets. Each nail should have 15 wire wrappings.
  4. Position the magnets as shown in the illustration. Use tape to secure the magnets to a base made of either foam core or packing cardboard. Remember that the magnets need to be placed so that they can direct the falling ball into the target zone.
  5. Slightly prop up the release edge of the ramp. Only a small rise is needed to insure a slow-moving ball. If the angle is too steep, the ball may roll too fast to be affected by the electromagnets.

PART 2 -Coordination Challenge

  1. Place a steel ball in the release location as indicated in the diagram.
  2. Release the ball and observe its slow roll down the incline. Turn on the upper electromagnet. The ball's path will be diverted towards the magnet. HINT: Here's where you'll need to fine tune your setup. The critical balance between the magnetic attraction and ball's roll depends upon several things such as the battery strength and mass of the steel ball. You'll have to reposition the magnets until the ball follows a path that is influenced by the attractive force of both magnets.
  3. As the ball rolls past the first magnet, switch on the lower circuit. The ball should be further diverted as it is attracted to this second magnet.
  4. Practice the release and the coordinated switching between circuits. Your goal is to have the ball roll into the target area.
  5. Practice, practice, practice. How far you can divert the ball's downward roll? Have you developed any tricks or techniques to improve your control?
QUESTIONS

  1. What caused the ball to move down the ramp?
  2. What force diverted the ball's downward roll?
  3. What produced the magnetic force?
  4. Suppose no magnetic attraction affected the ball's movement. Describe its path.
    How can this laboratory experience be applied to the challenges faced by FES?

COMMANDING COORDINATION
Even the simplest actions require an incredible amount of coordination. To explore this concept, identify a class leader. The leader stands in front of the class. Each student unlaces a shoe or sneaker. The leader must then instruct the class on how to tie a shoelace. The instructions can only be given orally. The leader is not allowed to physically assist anyone or demonstrate an action. The students are limited to only voice commands and must follow these commands as best they can. After this experience, discuss the elements of a coordinated sequential movement. Compare and contrast this experience with a "standing transfer" movement? How is it similar? How is it different?

SCIENCE IN YOUR WORLD
Have you ever examined an electric toothbrush? If so, you know that this device has its built-in battery located in the brush handle. Although the stand has an electrical connection to the wall outlet, the handle isn't wired to an electricity carrying wire. Its batteries charge through induction. Electricity that pulses through the stand produces an electromagnetic field. This field induces a current in a coil located in the toothbrush handle. This current charges the batteries in the toothbrush. Think about it. What is the advantage of this type of charging?
Why is this type of charging utilized for meeting the electrical demands of biotech devices implanted beneath the skin?

WEB CONNECTION

The Cleveland FES site
http://feswww.fes.cwru.edu/

An overview of the current clinical applications of FES
http://www.mpbe-sdh.demon.co.uk/fes.htm


The FES Society Homepage

http://www.bme.med.ualberta.ca/~fes/fes.html


Answers

The activities in this guide were contributed by Michael DiSpezio, a Massachusetts-based science writer and author of "Critical Thinking Puzzles" and "Awesome Experiments in Light & Sound" (Sterling Publishing Co., NY).

Academic Advisors for this Guide:

Corrine Lowen, Science Department, Wayland Public Schools, Wayland, MA
Suzanne Panico, Science Department, Fenway High School, Boston, MA
Anne E. Jones, Science Department, Wayland Middle School, Wayland, MA

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