3 Types of Cells the Heart Needs to Beat

EGELECTROCARDIOGRAPHY I I. Data and Calculations A: Heart Rate Complete the following tables with the lesson data indicated, and calculate the Mean as appropriate; TABLE 5.3 Recording: Condition 1. Supine 2. Seated 3. Start of Inhale 4. Start of Exhale Cardiac Cycle (40 Value) Mean (Calculate ) 1 80.21 79.58 83.33 2 81.85 78.33 85.83 3 79.26 77.51 85.83 80.44 78.47 84.99 84.74 83.79 85.95 84.83 B. Ventricular Systole and Diastole Condition 1. Supine 4. After Exercise C. Components of the ECG ECG Component Waves P QRS Complex T Intervals P-R Q-T R-R Segments P-R S-T T-P Normative Values Duration (seconds) .07-.18 .06-.12 .10-.25 Duration (seconds) .12-.20 .32-.38 .80 Duration (seconds) .02-.10 <.20 0-.40 Duration (ms) 1 Delta T Ventricular Systole 0.27400 0.38300 Ventricular Diastole 0.47500 0.22900 Duration (ms) 1 Delta T Recording 1 Cycle 1 2 3 Rec 1 Mean (Calc.) 0.064 0.14700 0.11900 0.07300 0.19200 0.16500 0.09100 0.155 0.16500 0.076 0.165 0.15 0.17300 0.28300 0.79400 0.17400 0.36500 0.74000 0.16500 0.34700 0.77600 0.171 0.332 0.77 0.05500 0.01800 0.42900 0.04500 0.01800 0.43800 0.05500 0.01900 0.24600 0.052 0.018 0.371 Rec 4 (One Cycle ) II. Questions A. Using data from table 5.3: 1) Explain the changes in heart rate between conditions. Describe the physiological mechanisms causing these changes. Although usually laying down has the lowest constant mean heart rate because of how the parasympathetic was in control, a possible reason why it is unlike the other group’s data is because of varying emotional states. For the seated data, it can be seen that in the first column under the cardiac cycle, it is higher compared to the two following data. This shows the brief sympathetic control at the beginning before parasympathetic took over while continuing to stay seated on the chair. In accordance with table 5.3, during inhalation, the heart rate mean is slightly higher than the exhalation because it is accommodating the increased venous return. On the other hand, during expiration, there is a progressive slowing in rate (Verrier et al., 2005). 2) Are there differences in the cardiac cycle with the respiratory cycle (“Start of inhaleexhale” data)? Yes, there are differences in the cardiac cycle with the respiratory cycle based on the start of inhale-exhale data, with the inhale slightly higher than the exhale. It is because the HR increased, which consequently increased O2 into the lungs, so the heart works faster to pump the blood during inhale, and the opposite happens during exhale. B. Using data from table 5.4: 1)What changes occurred in the duration of systole and diastole between resting and postexercise? As shown in the data, the duration of diastole decreased much larger when it transitioned from resting/supine to post-exercise. It is because the heart rate increased, which shortened the diastolic period significantly. On the other hand, the duration of systole between resting and post-exercise increased in the individual, based on the data. C. Using data from table 5.5: 1) Compared to the resting state, do the durations of the ECG intervals and segments decrease during exercise? Explain. The ECG intervals and segments during exercise decreased because the heart pumps fast, which consequently, the diastole has less time. In other words, the lowered ECG intervals and segments occurred due to shorter time for rest. 2) Compare your ECG data to the normative values. Explain any differences. All the ECG data were either in the range or near the normative values. The only data that was out of range were the R-R and QRS complex which could be due to the difference in the age of our subject and fitness level in comparison to the individuals who participated, to determine the normative values. 3) Compare ECG data with other groups in your laboratory. Does their data differ? Explain why this may not be unusual. Yes, the data of the two individuals differ. It is normal because individuals may have different heart sizes, which leads to cardiac output varying. Additionally, they have different fitness levels, height, age, and weight, which contributes as well. D. In order to beat, the heart needs three types of cells. Describe the cells and their function. 1) rhythm generators – they produce an electrical signal (SA node or normal pacemaker) 2) conductors – they spread the pacemaker signal 3) contractile cells – they mechanically pump blood (myocardium) E. List in proper sequence, starting with the normal pacemaker, elements of the cardiac conduction system. 1) SA node 2) Internodal pathway 3) Atrial Fibers 4) AV node 5) Bundle of His 6) Right bundle branch 7) Left bundle branch 8) Purkinje fibers F. Describe three cardiac effects of increased sympathetic activity, and of increased parasympathetic activity. Sympathetic The three cardiac effects of increased sympathetic activity are increased HR (heart rate) and SA node excitability, conductivity of electrical impulses through AV conductions, and the force of AV contractions. Parasympathetic The three cardiac effects of increased parasympathetic activity are decreased HR, conductivity of electrical impulses through AV conductions, and the force of AV contractions. In other words, the opposite of increased sympathetic activity cardiac effects. G. In the normal cardiac cycle, the atria contract before the ventricles. Where is this fact represented in the ECG? The PR segment represents in the ECG the fact that shows that in the normal cardiac cycle, the atria contract before the ventricles. In other words, it could also be represented in the P-wave and PR segment because it is the time impulse conduction from the AV node to the ventricular myocardiogram. Furthermore, the PR interval shows the time between the onset of atrial depolarization and the onset of ventricular depolarization (Klabunde, 2019). H. What is meant by “AV delay” and what purpose does the delay serve? AV delay is short for the atrioventricular delay, which determines the longest time interval between an atrial and ventricular excitation (Cardiocases, n.d.). It is important to have a delay between those two to allow time for the atrial contraction to complete the filling of the ventricles (Temple et al., 2013). I. What is the isoelectric line of the ECG? The isoelectric line of the ECG refers to the baseline of ECG tracing and showcases the resting membrane potentials. More specifically, it is the flatline of the end of the P-wave and the onset of the QRS complex, which is the PR segment that reflects the slow impulse conduction through the AV node (Rawshani, 2021). J. Which components of the ECG are normally measured along the isoelectric line? The components of the ECG that are normally measured along the isoelectric line are P-wave, QRS complex, and T-wave. K. Compared to the resting state, do the durations of the ECG intervals and segments decrease during exercise? Explain. The ECG intervals and segments during exercise decreased because the heart pumps fast, which consequently, the diastole has less time. In other words, the lowered ECG intervals and segments occurred due to a shorter time for rest.