FREE ESSAY ON ELECTROCARDIOGRAM

ELECTROCARDIOGRAM

Electrocardiogram Lab
Introduction
Electrocardiograms are used to obtain information about the function of the heart. An ECG
is a recording of the electrical activity of the heart made from electrodes placed on the
surface of the skin. Salt solutions are good conductors of electricity and can transfer
electrical activity to the skins surface. An ECG tracing shows the sum of the electrical
potentials generated by all the cells of the heart at any moment (Silverthorn, 1998).
Each point reflects depolarization or repolarization of a portion of the heart.
Depolarization is the signal for contraction. There are three major components of an ECG:
the p waves, which corresponds to depolarization of the atria (Silverthorn, 1998). The
qrs complex represents the progressive wave of ventricular depolarization (Silverthorn,
1998). And the t wave, represents the repolarization of the ventricles. When recording an
ECG, one active surface electrode is the positive and the other electrode is negative
while the third electrode is inactive. These electrodes are known as leads. Twelve leads
are now used to record ECG: the three limb electrodes plus the nine more electrodes
placed on the chest and trunk. ECG'S recorded from the different lead look different and
give information about different regions of the heart (Purves, 1998). An ECG provides
information on heart rate and rhythm, conduction velocity, and even the condition of the
tissues within the heart. Although obtaining and ECG is simple, interpreting some of its
subtleties can be quite complicated.
Purpose
To understand the electrical and mechanical events accociated with an ECG tracing
(DiFiori and Jarrell, 1998). To record and interpret ECG tracings under a variety of
physiological situations (DiFiori and Jarrell, 1998). To determine how changes in an ECG
can lead to changes in the heart rate (DiFiori and Jarrell, 1998).
1). What is the effect of the heart rate on a person who is sitting as opposed to
exercising?
Hypothesis
the heart rate is faster in a person who is exercising.
2) What is the effect of the heart rate on a person who is sitting as opposed to a person
demonstrating biofeedback?
Hypothesis
the heart rate could be the same if the individual is not totally relaxed, but if the
person goes to his or her special place that's very relaxing for them, the heart while
performing biofeedback could be lower than a person sitting down.
Methods
Set up an individual to record a normal ECG by placing a white electrode on the wrist, a
black electrode on the right ankle, and a red electrode on the lateral malleolus. Plug
the electrodes into port number two and choose lesson five and press setup. The biopac
unit will check the leads and adjust the recording on the screen. When your patient is
still, press the record button and the biopac unit will record for 60 seconds. If a
problem occurs, press the redo button and record again. After the setup is complete, take
the heart rate of the patient before each activity. The activities include sitting, lying
down, biofeedback, autonomic response, and response to exercise. During each activity,
record a ECG and make a record of the intervals and amplitudes.
Results
According to the t-test that compares the heart rate of the sitting and exercise
intervals, the person sitting has a lower heart rate than the person exercising. The
graph also, support the hypothesis. Also, in the chart and graph that compares the heart
rate of a person sitting and performing biofeedback, it shows that a person sitting have
a higher heart rate than a person performing biofeedback.
Discussion
During the early p-q intervals of an ecg, the atria and ventricles are relaxed while the
ventricles are passively being filled with blood. At the latter end of the p-q interval,
atrial contraction occurs forcing additional blood into the ventricles. At the beginning
of the qrs interval on an ecg reading, the mitral valve closes and the ventricles are at
edv (135ml). During the qrs interval, ventricular contraction occurs increasing the
pressure in the ventricle and the aorta. When the pressure continues in the ventricle
exceeds the pressure in the arteries, the aortic valve opens and blood is ejected. The
increased pressure continues through the t peak. The ventricles are now in esv (65ml) and
the aortic valve is closed. Now the ventricles are relaxed causing pressure to fall and
the cardiac cycle starts over again. This ecg reading was from a normal tracing. Keep in
mind that an ecg is easy to obtain, but there are some subtleties that are very complex.
Bibliography
LITERATURE CITED
Silverthorn, D.U.1998. Human Physiology: An Integrated Approach. Prentice Hall Press. NJ,
USA.
DiFiori, R.E. and P.E. Jarrell. 1998. Physiology Laboratory Book. Kendall/Hunt Publishing
Company. IA, USA.
Purves, W.K. 1998. Life: The Science of Biology. Sinauer Associates, INC. MA, USA.