answer all questions from protocal , apply graphs or tables , written results describing the data and interpretatin of the results (discussion) as well as the dependant and independant variables
BIOLOGY 4110 – GENERAL PHYSIOLOGY LECTURE
Lab Exercise #5 – Blood Pressure and ECGs
Auscultation of Heart Sounds
Auscultation of the heart means to listen to and study the various sounds arising from the heart as it pumps blood. These sounds are the result of vibrations produced when the heart valves close and the blood rebounds against the ventricular walls or blood vessels. The primary heart sounds S1 and S2 can be herd through a stethoscope.
First heart sound. Produced at the beginning of systole when the atrioventricular (AV) valves close and the semilunar (SL) valves open. This sound has a low-pitched tone commonly termed the “lub” sound of the heartbeat.
Second heart sound. Occurs during the end of systole and is produced by the closure of the SL valves, the opening of the AV valves, and the resulting vibrations in the arteries and ventricles. Due to the higher blood pressures in the arteries, the sound produced is higher pitched than the first heart sound. It is commonly referred to as the “dub” sound.
Blood Pressure Measurement
Determination of an individual’s blood pressure (BP) is one of the most useful clinical
measurements available. Overall, BP measurement provides information on the heart’s pumping
efficiency and the condition of the systemic blood vessels. In general, the systolic BP indicates the
force of contraction of the heart, whereas the diastolic BP indicates the condition of the systemic blood
vessels (for instance, an increase in diastolic BP indicates a decrease in vessel elasticity).
Figure 1. Normal pulsatile arterial blood pressure pattern. The dicrotic notch
reflects aortic semilunar valve closure.
Mean arterial pressure (MAP). This is the average effective pressure forcing blood through the circulatory system. Normal value is about 96-100 mmHg. Since the ventricles spend approximately one-third (1/3) of their time in systole and two-thirds (2/3) in diastole (Fig. 2), a simple average of the systolic and diastolic pressure values does not adequately estimate MAP. The MAP can be estimated with the following formula: MAP = DBP + PP/3 or 80 + 40/3 = 93.
We won’t be able to study blood pressure directly but we can study heart rate.
How to check your heart rate (https://www.health.harvard.edu/heart-health/want-to-check-your-heart-rate-heres-how) • At the wrist, lightly press the index and middle fingers of one hand on the opposite wrist, just below the base of the thumb. Alternatively, a digital fitness tracker may be used if available. • Count the number of beats in 15 seconds and multiply by four. That’s your heart rate. • Do not measure your heart rate within one to two hours after exercise or a stressful event. Your heart rate can stay elevated after strenuous activities. • Wait an hour after consuming caffeine, which can cause heart palpitations and make your heart rate rise. • Do not take the reading after you have been sitting or standing for a long period, which can affect your heart rate. Heart Rate Measurements Once you are confident of your ability to determine your heart rate, assess your heart rate in the following order: while lying down (supine), sitting, and standing. Be sure to acclimate to each postural position for at least 5 minutes before taking your heart rate readings (use a timer/watch). For each position, assess your heart rate five times with at least one min of rest between readings (this means you will collect 15 readings – five readings for each of 3 body positions).
After the final standing measurement, exercise vigorously for 5-10 minutes (run up and down stairs, jump rope, or jog in place) and as quickly as possible measure the supine heart rate after exercise (you will do this only once).
Prepare a bar graph comparing the mean std. error heart rate for each of the 3 body positions and the supine position following exercise.
Questions to address:
1) Did body position affect the heart rate and if so why?
2) Compare your supine mean heart rate before exercise with your after exercise
measurement. How do the changes noted relate to our ability to increase CO?
Although we won’t be able to record ECG tracings in the lab, we can study the components of a typical ECG. An example is included in Fig. 2. A Lead II ECG can be recorded with three electrodes located as follows:
Right arm negative, Left leg positive, Right leg ground.
The ECG is recorded at a speed of 25 mm/sec (5 large squares/sec), and the voltages are calibrated so that 1 mV = 10 mm (2 large squares) in the vertical direction. Therefore, each small 1-mm square represents 0.04 sec (40 msec) in time and 0.10 mV in voltage. Because the recording speed is standardized, one can calculate the heart rate from the intervals between different waves.
Figure 2. ECG standard calibration.
Use the ECG tracing below (Fig. 3) to calculate the P-R and Q-T durations for three separate tracings and determine the R-R Interval between three pairs of R waves to calculate the mean Heart Rate.
Figure 3. Normal Lead II ECG tracing.
Prepare a bar graph of the Mean std. error P-R and Q-T intervals and note the heart rate.
Question to address:
How might the measured parameters be affected by 5-10 minutes of vigorous exercise?
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