Exercise 31 ECGHeartsounds.docx

NU – AP 2

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ECG & Heart Sounds

Exercise 31A (modifed) Electrocardiogram (ECG), Heart Sounds, and Exercise Activity 1. !" !"#S #SE E  To  To perform perform an ECG recordin recording g in a human human subject, identify identify and and interpret interpret the waveforms in terms of depolarization and repolarization. Calculate ECG parameters such as Q! interval, " and QT segments, and analyze their signi#cance E$perimentally correlate heart sounds to electrical conduction in the heart and phases of cardiac cycle. Compare and analyze ECG recordings in rest and after e$ercise. •

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 The ability ability of the cardiac cardiac muscle to contract is is intrinsic, e.g. e.g. it does not depend depend on the nervous system to initiate its contraction, and it continues even if all connections are severed. Two systems e$ert their e%ects on heart activity& one is the autonomic nervous system, and the other is the instrinsic conduction system or nodal system of the heart. This consists of autorhytmic non'contractile cells specialized to initiate impulses throughout the heart. This way, the heart depolarizes and contracts in an orderly se(uential manner, and beats as a coordinated unit. !ee )igure *+.+ of your lab manual for the components of the intrinsic conduction system.  The electrical electrical currents currents generated generated and and transmitted transmitted through through the heart heart spread spread throughout the body and can be recorded with an electrocardiograph.  graphic record of that activity is called an electrocardiogram -ECG. )or analysis, the ECG is divided into segments and intervals -)ig.+ eview your te$tboo/ for a detailed description of the waveforms. 0hile ECG is a record of voltage and time, it re1ects electrical events happening in relatively large amount of muscle, so it does not re1ect the activity of nodal tissue only. 0e can infer that muscle contraction will follow the e$citation of muscle tissue, this is something that is not recorded in an ECG.  The main goal goal of this e$er e$ercise cise is for students students to become become familiar with with recording recording and interpreting di%erent cardiovascular parameters. Electrocardiograms -ECGs re1ect the electric activity of the heart. Cardiac parameters involve di%erent ECG intervals, as well as the 'wave amplitude -e$pressing the force of ventricular contraction and the heart rate. The characteristic heart sounds correspond to the closing of the 2 and semilunar valves. 3n the #rst part of the e$periment students will relate phases of the ECG pro#le with the heart sounds. 3n the second part, students will compare the ECG parameters recorded in rest and after aerobic e$ercise. P a g e  | 1

Last Revised on 2 March 2017 

NU – AP 2

iworx

ECG & Heart Sounds

%n te frst *art of this lab activity you will record the electrocardiogram -ECG of a group member while listening to the characteristic 4lub'dub5 heart sounds at rest. The 4lu+5 sound occurs during the early phase of ventricular contraction and is produced by closing of the atrioventricular valves, which prevents blood 1ow into the atria. 0hen the ventricles rela$, the blood pressure drops below what is in the artery and the semilunar valves close, producing the 4 du+5 sound. %n te second *art, you will only record ECG at rest and immediately after a short aerobic e$ercise. Two di%erent subjects should be recorded for the #rst and the second part.

EXPERIMENTAL SET-UP

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