Exercise Physiology Section 6 Cardiovascular Response to Exercise PDF

Section 6 Cardiovascular response to Exercise prof.dr.heba shawky Electrocardiogram ECG - Depolarization & repolarization of cardiac myocytes results in electrical currents. - These currents can be recorded by electrodes on the body surface(good conductor). - Each wave...

Section 6 Cardiovascular response to Exercise prof.dr.heba shawky Electrocardiogram ECG - Depolarization & repolarization of cardiac myocytes results in electrical currents. - These currents can be recorded by electrodes on the body surface(good conductor). - Each wave of ECG has characteristic shape, direction, duration and amplitude. Apparatus: Electrocardiograph: It consists of: 1- A sensitive galvanometer and amplifier to amplify the picked electrical current from the body surface. 2- Writing machine which has electrically heated stylus which inscribes on chemically treated graph paper. 3- The recording paper moves out of the apparatus at a constant speed of 25 mm/sec. The paper is divided into small squares 1 × 1 mm. Each 5 small squares are bounded by a heavier line. Each small square = 0.04 second. The horizontal calibration gives the amplitude of the waves in mV. 1 mV = 10 mm. 4- Connector cable: connects the electrode leads to the body surface. ECG machine  Description of the Normal ECG: 1-The P wave: represents atrial depolarization. 2-The QRS Complex: represents ventricular depolarization. It is formed of: a-Q wave which represents the depolarization of the interventricular septum. b-R wave which represents the depolarization of the 2 ventricles simultaneously. c-S wave which represents the depolarization of the thick posterobasal part of the left ventricle. 3-The T wave: represents ventricular repolarization. 4-U wave (which is usually absent) represents repolarization of the papillary muscles N.B.: Atrial repolarization is masked by ventricular depolarization. Important of PR interval: It is the interval from beginning of P wave to beginning of QRS complex. It represents the atrial depolarization and the duration of the atrioventricular conduction. Important of ST Segment: From the end of the S wave to the beginning of the T wave. During this time the heart is completely depolarized, and therefore the record is isoelectric. ECG Recording Analysis 1- Determination of the heart rate: HR = 1500/ Number of small squares between 2 successive R - Or HR = 300 / number of large squares in between each consecutive R wave. **60–100 beats/min (Normal) **>100 beats/min (Tachycardia) **