Download Cardiac Activities

Cardiac Activities
Introduction
The vertebrate heart is myogenic; that is the beat originates within the heart without the need for an external
stimulus to be delivered by the nervous system or the endocrine system. Although the heart generates its own
beat, external agents can alter the rate of the heartbeat and in some cases the strength of the heartbeat. Agents
that either increase or decrease the heart rate are called chronotropic agents. Chemicals that alter contractility of
cardiac muscle are called inotropic agents.
In this laboratory the surgically exposed frog heart will be used to study the effects of autonomic control of
heart rate. The effects of sympathetic stimulation can be simulated by applying epinephrine directly on the
heart. Indirectly, sympathetic effects on heart rate can be observed by blocking parasympathetic input with
atropine, a chemical that prevents acetylcholine action.
The effects of parasympathetic stimulation will be observed by applying acetylcholine directly on the heart.
Objectives
To observe and record ventricular systole and diastole in the frog heart.
To observe and record the effects of acetylcholine, atropine, and epinephrine on the frequency and
amplitude of cardiac muscle contraction in the frog heart.
To observe and record the inotropic effect of calcium and potassium on the frog heart.
Equipment
Force transducer
Shook
Calibration weight
BSL Pro template file: FrogHeart.gtl
Drug preparations:
Atropine 5%
Epinephrine 1:10,000
Acetylcholine 5%
Calcium chloride 1%
Potassium chloride 1%
Live frog
Amphibian Ringer’s solution
Droppers
Surgical gloves
Dissection scalpel
Dissection forceps
Dissection scissors
Dissection pins
Dissection probe
Dissection pan
Thread
Setup
Hardware:
Connect the SS12LA to Channel 1 on the MP30 as shown:
1. Turn on the MP30.
2. Launch the BSL Pro software on the computer.
3. Close the untitled window that opens.
4. Bring up the Frog Heart template by choosing File menu>Open>choose Files of type:
GraphTemplate (*gtl)>File Name: FrogHeart.gtl.
5. Close the stimulator window.
6. Hide channel 2.
7. Adjust the force transducer such that the hook holes are pointing down and so that the transducer is
level both vertically and horizontally.
8. Attach the small S hook to the transducer in the hole marked 0-50 grams.
Calibration:
1. Select MP30 > setup channels > channel 1 wrench icon (
) > scaling button.
2. With only the S hook attached to the transducer, click on the Cal1 button.
3. Attach the 50 gram weight to the S hook and stop any swinging motion.
4. Click on the Cal2 button.
5. Click OK to exit the scaling window.
6. Close out of setup channels.
Frog preparation
Dissect the double pithed frog as described below:
1. Place the frog on its dorsal surface in the dissecting pan.
2. Pin the upper and lower extremities of the frog securely to the rubber mat in the pan.
3. Cut the skin from the pelvic region to the throat of the frog.
4. Make a mid ventral incision along the linea alba starting in the pelvic region and continuing cranially
through the pectoral girdle.
5. Secure the segments of the sternum in such a way as to provide access to the heart.
6. Expose the frog heart by opening the pericardial sac.
7. Cut a piece of thread approximately 6 inches long.
8. Attach one end of the thread to the small hook provided using a secure knot.
9. Insert the hook into the apex of the heart.
10. Attach the other end of the thread to the S hook on the force transducer using a secure knot.
11. Carefully adjust the height of the force transducer so that the connection between the heart and the
transducer is relatively taut. BE CAREFUL NOT TO TEAR THE HOOK OUT OF THE HEART.
12. When the line is taut there should be approximately 4 inches of thread between the S hook and the
frog heart.
13. Make certain the thread is completely vertical.
Running the Experiments
Note: This recording is set up for the Append mode, so when the acquisition is stopped then restarted, data will
be added onto the previous data. A marker will automatically be inserted with a time stamp to indicate the new
segment start time. Change the marker identification to indicate the chemical preparation being applied to the
heart.
1. To save recorded data, choose File menu>Save As…>file type: BSL Pro files (*acq) File name:
(enter a name)>Save.
2. To erase all recorded date (make sure you have saved it first), and begin from time 0, choose:
MP30>Setup acquisition>Click on "Reset" button.
3. Record 5-10 cycles per segment. You do not need a continuous record; you do not need to record the
onset of the effects. A marker will appear each time you start the recording. Change the marker label
to indicate which conditions are being recorded.
4. Apply Ringer’s solution.
5. Click on the Start button and record 10 cycles of the normal heart rate.
6. Click on the Stop button.
7. Apply a few drops of epinephrine directly to the heart.
8. Wait approximately 5 minutes for the effects to become visible then click on the Start button and
record 10 cycles.
9. Click on the Stop button.
10. Flush the heart with Ringer’s solution and remove from the body cavity using the dropper provided.
Repeat 3 times then wait approximately 5 minutes for the heart to return to normal.
11. Apply 1 drop of acetylcholine directly to the heart.
12. Wait for the effects to become visible then click on the Start button and record 10 cycles.
13. Click on the Stop button.
14. Apply a few drops of atropine directly to the heart.
15. Wait for the effects to become visible then click on the Start button and record 10 cycles.
16. Click on the Stop button.
17. Flush the heart with Ringer’s solution and remove from the body cavity using the dropper provided.
Repeat 3 times then wait approximately 5 minutes for the heart to return to normal.
18. Apply a few drops of calcium chloride solution directly to the heart.
19. Wait for the effects to become visible then click on the Start button and record 10 cycles.
20. Click on the Stop button.
21. Flush the heart with Ringer’s solution and remove from the body cavity using the dropper provided.
Repeat 3 times then wait approximately 5 minutes for the heart to return to normal.
22. Apply a few drops of potassium chloride solution directly to the heart.
23. Wait for the effects to become visible then click on the Start button and record 10 cycles.
24. Click on the Stop button.
Analysis
Heart rate and force of contraction:
1. Set one channel 40 measurement window to bpm. Set all others to none.
2. Use the I-beam tool to measure a complete beat in the first part of the recording. Paste the
measurement in the journal.
3. Measure a few additional beats and paste their measurements in the journal.
4. Manually calculate the mean heart rate it in the journal.
5. Scroll to the recording showing the effects of epinephrine.
6. Measure a few beats in the recording and paste their measurements in the journal.
7. Calculate the mean heart rate and enter it in the journal.
8. Scroll to the recording showing the effects of acetylcholine.
9. Measure a few beats in the recording and paste their measurements in the journal.
10. Calculate the mean heart rate and enter it in the journal.
11. Scroll to the recording showing the effects of atropine.
12. Measure a few beats in the recording and paste their measurements in the journal.
13. Calculate the mean heart rate and enter it in the journal.
14. Scroll to the recording showing the effects of calcium.
15. Measure a few beats in the recording and paste their measurements in the journal.
16. Calculate the mean heart rate and enter it in the journal.
17. Scroll to the recording showing the effects of potassium.
18. Measure a few beats in the recording and paste their measurements in the journal.
19. Calculate the mean heart rate and enter it in the journal.
Duration of systole and diastole
1. Set one channel 40 measurement window to delta T and all others to none.
2. Measure the duration of systole and diastole for several beats in each part of the experimental
recordings.
3. Manually calculate the mean values for each phase and enter them in the journal where you
previously entered the measurements for heart rate.
4. Save the file to the hard drive.
Printing
1. Open a Word document.
2. Return to the BIOPAC file and highlight the areas of the graph to be printed.
3. Select Edit>Clipboard>Copy Graph.
4. Bring up the Word document.
5. Select paste.
6. To copy additional areas of the graph, return to BIOPAC, highlight the areas, copy them to the
clipboard, and paste into the Word document.
7. Copy the BIOPAC journal entries and paste them into the Word document.
8. When all graphs and journal entries have been transferred, save the Word document to the floppy
drive using your special group name.
9. Close Word and take the disc to the computer attached to the printer.
10. Select File>Print>choose number of copies>Print.
Use these data to complete the lab report.