HUMAN ANATOMY AND PHYSIOLOGY

Transcription

1 HUMAN ANATOMY AND PHYSIOLOGY NAME Detection of heart sounds. Clean the ear pieces of the stethoscope before using. The ear pieces should be pointing slightly forward when inserted into the ears because they fit more comfortably this way and hearing is facilitated. Listen to heart sounds at several positions on the chest wall. You may listen to your own heart and /or your partner's. You should be able to distinguish between the first and second heart sounds. The sounds are produced by the parts of the valves coming together and the turbulence this produces. a. Describe any change in loudness in either of the sounds when the stethoscope is moved to the each of the four locations indicated on the diagram. b. Where on the chest is the first sound the loudest? c. Where on the chest is the second sound the loudest? closing of the atrioventricular valves. Why would this create sound? d 1. The first sound involves the d 2. The second sound is caused by the closing of the semilunar valves. Why would this create a sound louder than the first one? (Hint: higher pressure pushes harder on the valves as they close) Perform one minute of moderate exercise and check the sounds again. e. An increase in exercise will increase preload. How would this increase affect the force closing ( and thus the sound) the atrio-ventricular valves? 1

2 f. Why is an increase in arterial pressure associated with increased afterload? How would this increased pressure affect the force of the closing of the semilunar valves. What effect would this have on the second heart sound? Determination of arterial pressure The blood pressure cuff or sphygmomanometer is placed around the biceps and inflated using a hand pump. The pressure on the arm is indicated by a gage attached to the cuff. DO NOT leave the cuff inflated on the arm for more than two minutes. When the cuff is inflated to about 140 mm of mercury pressure, the cuff will be applying enough pressure to close the brachial artery. While watching the pressure gage, slowly release the pressure in the cuff. When the pressure in the cuff is equal to the pressure in the artery, the systolic pressure has been reached and the pressure on the gage should be noted. When the systolic pressure has been reached, blood flow will resume. However, the compressed artery wall will cause turbulence as the blood squeezes through. These sounds can be detected by listening to the brachial artery with a stethoscope. Continue the slow release of pressure from the cuff and note the pressure at which the sound of blood squirting through the constricted artery first disappears. At this point the artery has returned to its normal diameter, and there is no more turbulence as the blood flows through it. This indicates the diastolic blood pressure. Average systolic and diastolic pressures for a 15 year old are 113 mm and 75 mm of mercury respectively. The average pressures for a 60 year old are 135 mm and 89 mm of mercury. Blood Pressure with Stethoscope = Blood Pressure with Electronic Device = a. How do your pressures compare to the average for 15 year-olds? b 1. Why were there no sounds when you first inflated the cuff? b 2. Why did you hear sounds as you let air out of the cuff? b 3. Why did the sounds disappear as you let out air from the cuff? 2

3 Determination of Venous pressure (demo) Stand against a whiteboard, estimate the level of the right atrium. Mark this point on the board. Hold your hand at your side and allow blood to accumulate in the veins in your hand. Slowly raise your hand until the veins in your hand collapse. Mark this point on the board. Measure the difference between the level of the right atrium the point at which the veins in your hand collapsed. The difference represents the venous pressure in mm of water, and the density of water is 1gm/ cm 3. Convert this pressure to pressure in mm of mercury (the density of mercury is about 13.5 g/cm 3 ). Complete your calculations here and enter your results below. Difference between atrium and vein collapse height = cm water, which would be equal to a column of mercury cm in height. Converting to mm, this would be mm Hg. The Electrocardiogram (ECG or EKG) An electrocardiogram (ECG or EKG) is a graphical recording of the electrical events occurring within the heart. In a healthy heart there is a natural pacemaker in the right atrium (the sinoatrial node) which initiates an electrical sequence. This impulse then passes down natural conduction pathways between the atria to the atrioventricular node and from there to both ventricles. The natural conduction pathways facilitate orderly spread of the impulse and coordinated contraction of first the atria and then the ventricles. The electrical journey creates unique deflections in the EKG that tell a story about heart function and health (Figure 1). Even more information is obtained by looking at the story from different angles, which is accomplished by placing electrodes in various positions on the chest and extremities. A positive deflection in an EKG tracing represents electrical activity moving toward the active lead (the green lead in this experiment). Figure 1 Doctors and other trained personnel can look at an EKG tracing and see evidence for disorders of the heart such as abnormal slowing, speeding, irregular rhythms, injury to muscle tissue (angina), and death of muscle tissue (myocardial infarction). The length of an interval indicates whether an impulse is following its normal pathway. A long interval reveals that an impulse has been slowed or has taken a longer route. A short interval reflects an impulse which followed a shorter route. If a complex is absent, the electrical impulse did not rise normally, or was blocked at that part of the heart. Lack of normal depolarization of the atria leads to an absent P wave. An absent QRS complex after a normal P wave indicates the electrical impulse was blocked before it reached the ventricles. Abnormally shaped complexes result from abnormal spread of the impulse through the muscle tissue, such as in myocardial infarction where the impulse cannot follow its normal pathway because of tissue death or injury. Electrical patterns may also be changed by metabolic abnormalities and by various medicines. 3

4 In this section you will use the EKG sensor to make a five second graphical recording of your heart s electrical activity. Be sure to record your EKG with both procedures! Procedure A. Standard limb lead EKG 1. Connect the EKG Sensor to the computer interface. Open Logger Pro. It should automatically open the file Analyzing Heart EKG from the Human Physiology with Vernier folder. In Open, go to the templates file and open HAP EKG Template. It should be set for 2 seconds. If not, select the icon to the right of the green collect button and select 2 seconds. 2. Attach three electrode tabs to your arms, as shown in Figure 2. Place a single patch on the inside of the right wrist, on the inside of the right upper forearm (distal to the elbow), and on the inside of the left upper forearm (distal to elbow). *** Remember, if you move during the recording of the ECG, electromyograms from other muscles will also be recorded. 3. Connect the EKG clips to the electrode tabs as shown in Figure 2. Sit in a relaxed position in a chair, with your forearms resting on your legs or on the arms of the chair. The EKG template is set to record for two seconds, which should be enough for one complete cycle. Use this EKG to show the stages and to measure the time intervals indicated in the table in results. BE SURE TO INDICATE PQTST and the time interval between them. When you are properly positioned, and relaxed, have someone click the green to begin data collection. You may need to do this several times before you get smooth, repetitive curves. Figure 2 4 Go to Print, in the print menu be sure to enter your name and make sure all black grids in NOT selected. Use the MGcart01-LJ1 printer 5. Now, go to the tab just to the right of the green button and change the time interval to 5 seconds. Delete your 2 second recording by going to the experiment menu and clicking on remove previous experiment. Set the program to record for 5 seconds. When you are properly positioned, and relaxed, have someone click the green to begin data collection. Once data collection is finished, click and drag to highlight four or five complete cycles (use the R peaks) and use this number to determine heart rate (beats per minute). The x value (shown at the bottom left) will indicate the time interval for the selected region. Follow the printing directions as in #4. 6. Tape your two charts on the data and analysis page. 4

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6 CUT OUT AND ATTACH YOUR SHORTER, 2 SECOND, LABELED ECG HERE Use your electrocardiogram and the information on the previous page complete the following. a. On the shorter graph label the parts (pqrst) of one cardiac cycle. b. Determine how much time is spent in the atrial phase (p-r interval) and ventricular phase(q-t interval) of your cycle. Be sure to show these on your ECG. Compare to the information on the table. Interval Your time Standard times (secs) P-R 0.12 to 0.20 QRS less than 0.12 Q-T 0.30 to 0.40 R-R b. Describe the source of each wave in the ECG wave pattern. p: qrs: t: 6

7 CUT OUT AND ATTACH YOUR LONGER TIME INTERVAL LABELED ECG HERE d. Calculate the duration of your cardiac cycle in seconds. To do this, measure the time interval between 4 or 5 R peaks. Be sure to show this on your ECG! # of cycles Total time seconds e. Using these numbers, calculate your heart rate in beats per minute. # of cycles/ Total seconds : X cycles/60 seconds 7

8 When things go awry. Atrial Fibrillation Ventricular Fibrillation 8