Download Cardio6Activity5A.pdf

6th Grade Activity 5: “The Rhythm of the Beat”
Learning goals:
After completing this exercise students should be able to:
• Understand the purpose of an EKG.
• Explain that an EKG records the electrical activity of the heart.
Have you ever watched a television show or movie about doctors and hospitals and seen a patient
hooked up to a machine that makes a pattern like this?
Did you remember ever hearing about something called and EKG or ECG?
In this activity, you will learn about something called an electrocardiogram or EKG (sometimes
called ECG). An electrocardiogram records the electrical activity of the heart. Doctors use EKGs to
detect and diagnose heart problems.
In the last activity, you learned about the structure of the heart. You learned that heart has four
chambers:
• Right atrium
• Left atrium
• Right ventricle
• Left ventricle
The heart pumps blood in a regular rhythm. Blood is moved through the heart, to the lungs, and to the
rest of the body by the force of the heart muscles contracting. When the atria contract, they squeeze
blood into the ventricles. When the ventricles contract, they squeeze the blood into the arteries leaving
the heart. The heart muscles contract, on average, about 72 times every minute. This is called the
heart rate. The heart rate is controlled by electrical charges generated by nodes in the heart. These
electrical charges stimulate the heart muscles to contract. Did you know that cells in your body can
generate electrical charges? The heart has two centers of specialized cells that generate regular
electrical charges:
• Sinoatrial or SA node
• Atrioventricular or AV node
The SA node is sometimes called the heart’s pacemaker because it sends the electrical signal that cause
the atria to contract in a regular rhythm and rate.
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The AV node transfers the electrical signal from the atria to the ventricles, causing the ventricles to
contract.
SA Node
AV node
The SA node is sometimes called the heart’s pacemaker because it sends the electrical signal that
cause the atria to contract in a regular rhythm and rate. The AV node transfers the electrical signal
from the atria to the ventricles.
You will now have the opportunity to take your own EKG!
I. EKG Procedure:
1.) Divide the class into groups of three or four. Each group should gather the following materials:
• Computer
• EKG sensor
2.) Start the computer.
3.) Plug the USB Link into the computer.
4.) Plug the EKG sensor into the USB Link.
5.) A window will appear on the computer display that says, “I found a new EKG Sensor. How would
you like to use it?”
6.) Click “Launch Data Studio”.
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7.) Close the “Digits” window by clicking the red circle in the upper left corner.
8.) Click “OK” in the message dialog box.
9.) Do the following for each person in the group:
a.) Stick three EKG electrode tabs to your skin. Stick one on the inside of your left arm just below the
elbow. Stick one on the inside of your right arm just below the elbow. Stick one to the inside of your
right wrist.
Green (negative)
Black (ground)
Ä
Red (positive)
b.) Using the diagram above to match the colors to the right locations, connect the EKG electrode clips
to the tabs.
c.) Click the “Start” button. The start button is in the top left corner and has a green triangle.
d.) After about 20 seconds, click the “Stop” button.
e.) Print your EKG.
10.) Repeat Step 9 for the rest of the people in your group.
11.) Disconnect your EKG sensor and shut down the computer.
II. Questions:
Write your answers on a separate sheet of paper.
1.) What is the EKG sensor sensing from your body?
2.) What parts of the heart create the electrical charge that is record by the EKG?
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III. Situation in the ER:
Imagine that you are an emergency room doctor. You are working on a patient, who collapsed during
a family barbeque. The patient is unconscious. When the patient is first brought in, the nurses hook up
an EKG monitor.
This is what the patient’s EKG looks like when he is first hooked to the monitor at 4:17 PM.
4:17 PM
1.) Does this appear to be a normal pattern?
Write your answer on a separate sheet of paper.
At 4:26 PM, the patient’s EKG changes and looks like this:
4:26 PM
2.) Is this a normal EKG pattern? What is different about it?
Write your answer on a separate sheet of paper.
3.) What do you think will happen to this patient if the heart continues to create an EKG pattern that
looks like this?
Write your answer on a separate sheet of paper.
4.) What could you do to restore the normal EKG pattern? (Think about things you may have seen on
TV or in the movies.)
Write your answer on a separate sheet of paper.
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Health care professionals sometimes use an electrical shock to restore normal heart rhythm. You may
have heard of a “crash cart” or seen doctors on TV yell “Clear!” and apply paddles to someone’s chest
to give them a shock. This machine is called a defibrillator.
At 4:28, you use a defibrillator on your patient, and the EKG monitor shows the following pattern:
4:28 PM
Defibrillator
applied
5.) Does the patient’s EKG appear to return to normal?
Write your answer on a separate sheet of paper.
EKG traces adapted from: ECG Library. (http://www.ecglibrary.com/ecghome.html) 1995-2002. Dean Jenkins and Stephen
Gerred.
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