ECG+Lab - 125:315 BME MEASUREMENTS AND ANALYSIS LABORATORY...

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125:315 BME MEASUREMENTS AND ANALYSIS LABORATORY SPRING 2011 BIOMEDICAL SIGNAL PROCESSING & ECG Rutgers, The State University of New Jersey Department of Biomedical Engineering Room 121
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Lab 2: Biomedical Signal Processing & ECG Page 2 of 13 Biomedical Signal Processing & ECG I. Objectives The objectives of this laboratory exercise are to: 1. Develop an understanding of the electrophysiology of the heart and the principles of measurement & analysis of the electrical activity of the heart. 2. Use the BIOPAC data acquisition system to record and analyze your own ECG signal. 3. Design a data acquisition system using LabView to model or mimic the BIOPAC data acquisition system. 4. Modify the LabView setup to understand the effects of low, high, and band-pass filters on ECG signals. 5. Learn to interpret the ECG waveform and understand its biological and clinical significance. II. Introduction II.1 Origin of Bioelectric Signals Galvani demonstrated in the eighteenth century that most physiological processes are accompanied by electrical changes. Two internal sources, namely the muscles and the nerves, produce multiple electrical signals. The movement of ions generates potential differences that are related to normal muscular contraction. This difference in potentials can be measured by electrodes on the surface of the skin. Resting Potential Bioelectric signals are produced at a cellular level when cell ionic concentrations change with respect to concentrations outside the cell. Some of the most common ions inside and outside the cell are Na + , K + , Ca 2+ , and Cl . Ionic species are not distributed equally on the two sides of a membrane. Normally, when a cell is in its resting state, the inner surface of the cell membrane is negatively charged with respect to the outer portion of the membrane. This occurs because of ion channels and an “active Na/K ATP pump” that uses molecular energy in the form of ATP, to allow more positive ions leave the cell (3 Na + ) than enter the cell (2 K + ). The potential difference across the cell membrane caused by unequal charge distribution is called the resting potential . The internal resting potential within a cell is usually between -70 and -90 mV with respect to the outside of the cell. Depolarization When the cell is excited or stimulated, the inner side of its membrane becomes temporarily less negative, with reference to the outer surface of the membrane. This happens due to the opening of Na + channels, letting the Na + ions pass into the cell down its concentration gradient. As a result, the cell potential changes to be approximately +20 mV. This process of the cell becoming more positive inside is termed depolarization .
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Lab 2: Biomedical Signal Processing & ECG Page 3 of 13 Repolarization The return of the cell membrane potential to the resting potential where inner the surface of the membrane is again negative with respect to the outer surface in a short time is called repolarization . In skeletal muscle cells , repolarization occurs quickly as voltage-gated K + ion channels open, allowing K + ions to rush outside the cell down its concentration gradient. Ionic flow during excitation in
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