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Lab 3
Conduction System of the Heart and Electrocardiography
Monitoring an ECG(EKG) - Introductory Information
The figure below identifies the deflections on an ECG. Figure 18.16 in the
text.
Refer to Exercise 31 in the lab manual for more information. The
deflections on the ECG are called the P wave, QRS complex and T wave.
Pulse – Introductory Information. See Exercise 33A in the lab manual
for more information.
The pulse refers to the surges of pressure and recoil in the large arteries
near the heart as the left ventricle contracts and relaxes. To palpate the
pulse, put the tips of the first two or three fingers over the radial artery on
the lateral part of the wrist, just above the thumb.
Estimating Systole and Diastole Using the ECG
This exercise is designed to estimate the length of time any part of the
heart (either atria or ventricles) is in systole and the length of time both are
in diastole (the quiescent period). In a typical 0.8-second cardiac cycle,
systole is about 0.4 second and complete diastole is about 0.4 second. The
actual resting lengths will depend on the length of the cardiac cycle of
each individual at rest.
Atrium
Cardiac
Cycle
75 BPM
0.8 s
Ventricle
S
.1s
D
.1s
D
.1s
D
.1s
D
.1s
D
.1s
D
.1s
D
.1s
.1s
.1s
.1s
.1s
.1s
.1s
.1s
.1s
D
.1s
S
.1s
S
.1s
S
.1s
D
.1s
D
.1s
D
.1s
D
.1s
Quiescent Period
Here are estimated times for some parts of the ECG. You can see that
typically the systole estimate (beginning of P to beginning of T ) is about 0.4
seconds.
Feature
Description
The PR interval is measured from the beginning of the P wave to the
beginning of the QRS complex. The PR interval reflects the time the electrical
PR or P-Q
impulse takes to travel from the sinus node through the AV node and entering
interval
the ventricles. The PR interval is therefore a good estimate of AV node
function.
The QRS complex reflects the rapid depolarization of the right and left
QRS
ventricles. They have a large muscle mass compared to the atria and so the
complex
QRS complex usually has a much larger amplitude than the P-wave.
S-T
The ST segment connects the QRS complex and the T wave. The ST segment
segment represents the period when the ventricles are depolarized. It is isoelectric.
Duration
.12-0.2 s
.08-.12s
08-.12s
When you do your measuring, if your numbers seem to be extremely
different, consider re-measuring.
Monitoring an ECG (EKG) Using Vernier Equipment
Record Computer MCC Asset Tag Number here ________________
(This is on the top of the computer.)
Directions for Using the Vernier System
Starting Up
1. Turn on the computer and follow directions to log on.
2. On the Windows desktop, select Logger Pro and close the “tip of the
day” window
3. Select File, Open
4. Select Biology With Computers
5. Select Experiment 28: Monitoring EKG
Note: these directions may be slightly different on some of the laptops
and I will help you sort it out in lab.
On the screen is a recording chart and above the chart are menu choices
and control buttons. You will need to use File, Analyze, Insert and
<Collect> in this exercise.
Directions for Recording the ECG
1. Open the Insert menu and select Text Annotation. Move the cursor to
the box and type in a title to identify the ECG when it prints.
2. Recording ECG While Sitting Quietly. This is the baseline data
against which you can compare data from the exercise experiment.
Select a subject who is willing to exercise to a point that causes heavy
breathing. Ask the subject to sit quietly at the computer in a relaxed but
upright position with arms at the side or on the lap. Attach electrode
tabs firmly on the insides of the right and left forearms, just below the
right and left elbows. Also attach an electrode tab on the inside of the
right wrist.
3. Attach the green clip to the tab on the right forearm, the red clip to the
tab on the left forearm and the black clip to the tab on the right wrist.
Note: There are picture directions for attaching the EKG electrodes on
the electrode box.
4. When everything is ready, click on the <Collect> button. The computer
will collect data for five seconds. If the data look similar to Figure 31.2,
continue on. If the data look different, check the electrodes, remind the
subject to relax, and not to move, laugh or talk. Repeat the data
collection until you get four good tracings on a single screen.
While you are recording the ECG, record the pulse rate per minute.
5. When data collection ends, select File, Save As, and select My
Documents and save the file as subject's initials baseline. For example,
Linda S. Kollett would be lsk baseline.
Data Analysis
1. Once you have saved the data, click on the Analyze menu and choose
Examine. A cursor line will appear on the graph and a box will appear
in the upper left corner displaying voltage (V) and time (sec.). Moving
the line allows you to measure voltage and time (distance) on the
graph. We are only interested in time in this experiment.
3. Measuring Systole. Select one of the tracings and put the cursor line at
the beginning of the P wave and note the time. This is A. Then move it
to the beginning of T and note the second time. This is B. Leave the
cursor in place here, as it will be the starting point for the next
measurement. Record the two times in the workbox below.
Subtract the first time at beginning of P (A) from the second time at the
beginning of T (B). The difference between the first time and the second
time is the amount of time the heart is in atrial and ventricular
depolarization and is a reasonable measurement of time in systole.
After you have done the calculations, record the data in the Systole
Data Work Table as Length of Systole for ECG 1.
4. Measuring Diastole. Using the time value at the beginning of T as a
starting point (B), move the cursor to the beginning of the next P wave
and record the time. This is C. This represents repolarization and
diastole. Record the two times in the workbox below. The first time
should be identical to the second time of the first measurement (B).
Subtract the time at the beginning of T (B) from the time at the
beginning of the next P wave (C) to calculate the approximate length of
diastole.
Record the time difference under Length of Diastole for ECG 1 in the
Diastole Work Table.
5. Repeat the measurements with two other tracings on the same graph.
Record on the Data Tables as
 Length of Systole ECG 2
 Length of Systole ECG 3


Length of Diastole ECG 2
Length of Diastole ECG 3.
Baseline Pulse Rate _________________ beats per minute
Work Table - Baseline Systole Data
Tracing
A
Start
Time
B
B-A
End Time Length of
Systole
ECG 1
ECG 2
ECG 3
Average
time for
systole
Work Table - Baseline Diastole Data
Tracing
B
Start
Time
C
End Time
C-B
Length of
Diastole
ECG 1
ECG 2
ECG 3
Average
time for
diastole
Note: If the pulse rate seems high for a resting pulse, let
the subject relax and repeat the baseline recordings.
(Average pulse rate is 70-76 beats per minute.)
Name________________________________ Lab Session _____________
Experiment 1 The Effect of Exercise on the Heart
Write the hypothesis you have proposed in your introduction about the
effect of strenuous exercise on the lengths of systole and diastole in the
heart and the change in pulse rate immediately after exercise, and after 1
minute and 4 minutes of recovery. Pulse rate and length of time for
systole and diastole are the only things we are measuring. Be sure your
hypothesis is complete – has 3 parts to it. Use “I think”, not “I believe.”
Hypothesis:
Method
1. Use the same subject as you used for the baseline recording.
2. Remove the electrodes, but do not remove the electrode tabs.
3. Ask the subject to exercise strenuously for 3 minutes and then sit
down.
4. Immediately reattach the electrodes and begin recording an ECG.
5.
Record at least 4 ECG tracings on the screen immediately after
exercise (label as initials_0 min and Save in My Documents)
Record the pulse rate.
6. Record at least 4 ECG tracings on the screen one minute after
exercise (label as initials_1 min and Save in My Documents)
Record the pulse rate.
7. Record at least 4 ECG tracings on the screen 4 minutes after
exercise (label as initials_4 min and Save in My Documents)
Record the pulse rate.
8. Do the same systole and diastole measurement calculations for 3 of
the tracings that you did for the baseline recording. Record the
data.
9. Calculate the average times for systole and diastole for each event
and record in the charts below.
10. Use the data from the Baseline Systole and Diastole Work Tables
as Baseline Data
11.
Work Tables. Record Raw Data Here for the Experiments
Immediately After Exercise
Pulse Rate ___________________
Systole
Tracing
Systole Data Work Table
A
B
Start
End Time
Time
B-A
Length of
Systole
ECG 1
ECG 2
ECG 3
X
Diastole
Tracing
ECG 1
Average
time for
systole
Diastole Data Work Table
B
C
C-B
Start
End Time Length of
Time
Diastole
ECG 2
ECG 3
X
One Minute After Exercise
Average
time for
diastole
Pulse Rate ___________________
Systole
Tracing
Systole Data Work Table
A
B
Start
End Time
Time
B-A
Length of
Systole
ECG 1
ECG 2
ECG 3
X
Diastole
Tracing
ECG 1
ECG 2
Average
time for
systole
Diastole Data Work Table
B
C
C-B
Start
End Time Length of
Time
Diastole
ECG 3
X
Average
time for
diastole
Four Minutes After Exercise
Pulse Rate ___________________
Systole
Tracing
Systole Data Work Table
A
B
Start
End Time
Time
B-A
Length of
Systole
ECG 1
ECG 2
ECG 3
X
Diastole
Tracing
Average
time for
systole
Diastole Data Work Table
B
C
C-B
Start
End Time Length of
Time
Diastole
ECG 1
ECG 2
ECG 3
X
Average
time for
diastole
Combined Average Data – Use This in Results
Pulse Data Table
Baseline
Immediately after
beats/min. Exercise b/min.
One Minute after
Exercise b/min.
Four Minutes after
Exercise b/min.
Systole Data Table
Baseline
Systole
Immediately
after Exercise
One Minute
after
Exercise
Four
Minutes
after
Exercise
Immediately
after Exercise
One Minute
after
Exercise
Four
Minutes
after
Exercise
Average time
for systole
Diastole Data Table
Baseline
Diastole
Average time
for diastole
Please note: A lab report is not an exercise in creative writing. It has a
very specific format. Please read over the directions carefully and talk
with me if you have questions. I will collect these reports, read them and
return them with comments and suggestions. The next time I read it will
be for a grade. You are welcome to discuss it with me, but I will not read
it again.
Preparing a Modified Lab Report
1. Prepare a modified lab report. It must be typed or word-processed.
This will be worth 5% of your grade.
2. Be sure it has a cover sheet with the title 1/3 from the top of the
sheet, centered and your name, the date and the class at the bottom
right.
3. Be sure it contains all the parts of a scientific paper and uses the
correct citation format. Label each section in bold
a.
b.
c.
d.
e.
f.
Title Page
Introduction – including a clearly stated hypothesis.
Methods
Results
Discussion
Literature Cited
4. The report should have at least 3 citations and at least 2 citations
from outside sources (not the text, lab manual or class notes).
5. The rough draft of this report is due ___________________. This
will give you time to review my comments and submit a final draft.
6. The final draft is due the last day of classes, 5/11/11 but I suggest
that you turn it in well before that date.
The Modified Lab Report
Grading Rubric
Title or Cover Page
Introduction
Methods
Results
Discussion
Literature Cited
Grammar and Spelling
5 points
30 points
10 points
30 points (text, table and graph)
10 points
5 points (at least 3, at least 2 outside sources)
10 points
Title or Cover Page
1. Title 1/3 from the top of the sheet, centered and your name, the date and
the class at the bottom right.
2. Sections of the paper should be clearly marked with headings.
(Introduction, Methods, etc.)
Introduction
You should have handed in a draft introduction with the sections numbered.
After my comments you should rewrite this in paragraph form for the lab report
Methods
This section provides all the methodological details necessary for another
scientist to duplicate your work. We will use a bit of a shortcut here.
For this exercise, include the type and length of exercise your subject chose to do.
Then write “Refer to instructions in the lab handout” for the rest of the methods.
Results
This section presents the results of the experiment but does not attempt to
interpret their meaning. The trick to writing a good Results section is knowing
what information to include or exclude. You will not present the raw data that
you collected, but rather you will summarize the data with text, tables and/or
figures. Write out the results of your study in this section (10 points). Prepare a
table (10 points and a graph (10 points).
Refer the reader to a table or figure where they can see the data for themselves.
Use the parts of the tables highlighted in red, and also include a graph. Give the
table a title above the table. Label the graph as a figure below the graph.
Example of a Table
Example of a Graph
Table 1. Title
Figure 1. Title
Number tables and figures separately beginning with 1 (i.e. Table 1, Table 2,
Figure 1, etc.).
Do not evaluate the results in this section. Report only what you found; hold all
discussion of the significance of the results for the Discussion section.
Brief or Modified Discussion
In this section look back on your hypothesis in the Introduction section. State
whether your data supports or does not support your hypothesis. Do not use
the words prove or disprove here!
If your data do not support your hypothesis, state what hypothesis they do
support.
If necessary, note problems with the methods and explain any problems you
suspect in the data. Describe how the problems might affect the conclusions.
Literature Cited
This is the last section of the paper. Here you should provide an alphabetical
listing of all the published work you cited in the text of the paper. Only include
the works you actually cited in the text of your paper.
For papers published in journals you must provide the date, title, journal name,
volume number, and page numbers.
For books you need the publication date, title, publisher, and place of
publication.
Please include at least 3 references. You may use your text as a reference, but be
sure that at least 2 sources are outside sources (neither text, lab manual or
handout).
Literature Cited format examples.
Papers in Journals
Djorjevic, M., D.W. Gabriel and B.G. Rolfe. 1987. Rhizobium: Refined parasite of
legumes. Annual Review of Phytopathology 25: 145-168.
Jones, I. J. and B. J. Green. 1963. Inhibitory agents in walnut trees. Plant
Physiology 70:101-152.
Books
MacArthur, R.H. and E.O. Wilson. 1967. The Theory of Island Biogeography.
Princeton University Press, Princeton, N.J.
Internet Sources
For web sites, provide name and URL.