Lab 3. Conduction System of the Heart and Electrocardiography

Transcription

1 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 in the text. arson Education, Inc., publishing as Benjamin Cummings 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.

2 Estimating and 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 S D D D D D D D.1s.1s.1s.1s.1s.1s.1s.1s Cardiac Cycle 75 BPM 0.8 s.1s.1s.1s.1s.1s.1s.1s.1s Ventricle D S S S D D D D.1s.1s.1s.1s.1s.1s.1s.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 Duration PR or P-Q interval QRS complex S-T segment 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 impulse takes to travel from the sinus node through the AV node and entering 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 ventricles. They have a large muscle mass compared to the atria and so the QRS complex usually has a much larger amplitude than the P-wave. The ST segment connects the QRS complex and the T wave. The ST segment represents the period when the ventricles are depolarized. It is isoelectric s s s When you do your measuring, if your numbers seem to be extremely different, consider re-measuring.

3 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.

4 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. 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 Data Work Table as Length of for. 4. Measuring. 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 for in the Work Table. 5. Repeat the measurements with two other tracings on the same graph. Record on the Data Tables as Length of Length of Length of Length of.

5 Baseline Pulse Rate beats per minute Work Table - Baseline Data A Start B End B - A Length of systole Work Table - Baseline Data B Start C End C - B Length of diastole Note: If the pulse rate seems high for a resting pulse, let the subject relax and repeat the baseline recordings. ( pulse rate is beats per minute.)

6 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 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.

7 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 and Work Tables as Baseline Data 11. Work Tables. Record Raw Data Here for the Experiments Immediately After Exercise Pulse Rate Data Work Table A B Start End B-A Length of X systole Data Work Table B C C - B Start End Length of X diastole

8 One Minute After Exercise Pulse Rate Data Work Table A B Start End B-A Length of X systole Data Work Table B C C - B Start End Length of X diastole

9 Four Minutes After Exercise Pulse Rate Data Work Table A B Start End B-A Length of X systole Data Work Table B C C - B Start End Length of X diastole

10 Combined 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. Data Table time for systole Baseline Immediately after Exercise One Minute after Exercise Four Minutes after Exercise Data Table Baseline Immediately after Exercise One Minute after Exercise Four Minutes after Exercise time for diastole

11 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. Title Page b. Introduction including a clearly stated hypothesis. c. Methods d. Results e. Discussion f. 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.

12 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.

13 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.

14 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 Rhizobium: Refined parasite of legumes. Annual Review of Phytopathology 25: Jones, I. J. and B. J. Green Inhibitory agents in walnut trees. Plant Physiology 70: Books MacArthur, R.H. and E.O. Wilson The Theory of Island Biogeography. Princeton University Press, Princeton, N.J. Internet Sources For web sites, provide name and URL.