Lab report 3 cardiac output PDF

Preview

Summary

anatomy and physiology "heart" lab report...

Description

Lab report 3: Cardiac Output Background: Cardiac output is the volume of blood ejected from the left/right ventricle into the aorta/pulmonary trunk each minute. This could be measured through this simple formula: CO = stroke volume (mL/beat) X heart rate (beats/min) Cardiac output increases when a person is exercising compared to when at rest, because as they exercise, their muscles require more oxygen, when there is a high demand for blood, your heart pumps faster so it can move blood out to the body faster. If there is an increased demand for blood from your body, your sympathetic system would help deliver that. In contractile fibers, norepinephrine enhances calcium entry through the calcium gates thereby increasing contractility, therefore greater volume of blood ejected during systole. We can measure our heart rate (through ECG), pressure, and volume in ventricle, clinically. Our heart rate is regulated by the autonomic nervous system and by chemicals such as hormones. It's mostly controlled unconsciously by sympathetic system, impulses in the cardiac accelerator nerve trigger the release of norepinephrine, which binds to beta- 1 receptors on cardiac muscle fibers. In SA, it speeds the rate of depolarization to make the pacemakers fire impulses more rapidly and therefore increasing the heart rate, and parasympathetic system, in which vagal axons terminate in the SA node, AV node and atrial myocardium, which release acetylcholine, which then decreases the heart rate by slowing down the rate of depolarization in autorhythmic fibers, however our heart rate could also be consciously controlled by performing the valsalva maneuver, which is when a person forcefully tries to exhale through a closed airway. Our blood pressure changes to maintain homeostasis, by maintaining body tissue’s integrity. Blood pressure changes due to constriction or dilation of blood vessels. Performing the Valsalva maneuver causes the abdominal veins to be compressed, thus pushing it's venous content towards the heart which causes an increase in blood pressure, and decreases heart rate as holding your breath builds up pressure in the chest, which causes restriction of blood flow to the right atrium, therefore increasing the blood pressure, the autonomic system senses that and constricts the blood vessels which bring the blood pressure to normal and ANS stimulates parasympathetic system which decreases the heart rate. Hypothesis: For this experiment I hypothesised that our blood pressure and heart rate would be about normal at rest and that both our heart rate and blood pressure would increase while performing the valsalva maneuver and exercising as there will be a lot of pressure built up,which will cause the increase of heart rate and because the blood flow is restricted due to the pressure, it will pump out much faster when you exhale, therefore, increasing the blood pressure. During exercise, it would increase as our muscles demand more oxygen and blood when working hard. Results: Time 0

Valsalva Maneuver

Exercise

HEART RATE

70

68

68

65

61

153

156

BLOOD PRESSURE

108/78

110/80

103/78

111/97

131/95

127/79 119/87

154 101/79

Observations: While running up and down the stairs for this experiment, me and my group members experienced being light headed, nauseous, out of breath, hot and increasing and hearing heartbeat. Discussion: Valsalva maneuver is performed when an individual forcefully exhales against a closed airway. People use this technique to balance pressure in the ears and to help restore normal heartbeat when heart starts beating too fast. There are four phases of this technique: Phase 1: Causes pressure in the aorta to increase and a spike in your blood pressure Phase 2: Blood is restricted from going to the heart due to the pressure build-up, which decreases the stroke volume and heart rate. The ANS sense this and constricts the blood vessels which help blood pressure goes back to normal and heart rate increases. Phase 3: Blood pressure falls temporarily, allowing expansion of pulmonary vessels and the aorta, which causes a drop in stroke volume and increases the amount of aortic volume. During this phase, the blood begins to enter the chest and the heart, increasing the cardiac output. Phase 4: Blood rushes back to heart, blood flow goes back to normal, blood pressure temporarily rises because blood vessels are still constricted and heart rate decreases. I hypothesized that at rest, our blood pressure and heart rate would be about average and it would not change when measured more than once, but we observed that it infact did, just by a little (108/78 → 110/80) and a few factors could contribute to that such as, sitting position or arm position of the person measuring the blood pressure, the person talking,or wrong replacement of the cuff or the wire. For exercise, I hypothesized that our heart rate and blood pressure would increase as our working muscles will demand more oxygen and blood, therefore the heart will have to work harder and faster in order to supply the muscles,and thats what we observed in our results as well. The blood pressure increased about 20 mm Hg (108/78 → 127/79), from when it was at rest to after exercising. The heart rate was more than double (70 → 153) after exercising than what it was at rest. For valsalva maneuver, I initially hypothesized that both our heart rate and blood pressure would increase, but thats not what we saw in the results and that was because during phase 4, the venous blood returning to the heart, increases blood pressure for sometime and ANS stimulating the parasympathetic system decreases heart rate. Heart rate went down to 65 and blood pressure rose up to 111/97 from 103/78 (at rest). Conclusion: From this experiment, I learned how our heart rate and blood pressure changes (significantly sometimes) depending on what we are doing. I learned all the phases of valsalva maneuver and what happens in each phase and how they impact our blood pressure and heart rate. I had no knowledge about the valsalva maneuver before this lab, now I know how this can be used medically and could be really helpful to people. Some of the things we can improve in the future, in order to accurately do this experiment are, make sure no other factors are causing the difference in blood pressure and could use our time wisely so that we could have gotten another round for measuring valsalva maneuver or try the carotid massage....