Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Blood Pressure changes reflected by Posture and Activity Anatomy and Physiology 503 Lab Rebecca Levenstein Tara Gionfriddo, Giselle Hardy, Deniahn Wade, (and others) October 15, 2013 Introduction: The purpose of this experiment is to measure the changes in blood pressure and pulse rate of two subjects with varying degrees of fitness, based upon posture changes and physical activity, and then calculate and compare the mean arteriole pressure during each phase, and also to measure the changes in pulse pressure and blood pressure when spelling tests are administered. Blood pressure is the amount of force exerted on the vessel walls, and is expressed in mm^3 (Marieb and Hoehn 2012). Blood always flows from a higher pressure gradient to a lower gradient, and is forcibly generated through blood vessels by the pumping mechanism of the heart. Pressure results from the presence of peripheral resistance, such as thickening of the blood and the narrowing of the diameter of the vessel (Marieb and Hoehn 2012). Normal blood pressure is 120/80 mm^3. The number on the top expresses systolic pressure, or the pressure exerted during the peak of the ventricular contraction phase, and the bottom number expresses diastolic pressure, which is the pressure exerted at the time when the heart is least contracted. Pulse pressure, also referred to as heart rate for this experiment, is the difference between diastolic pressure and systolic pressure (PP = DP – SP). Pulse pressure is measured by counting the number of pulsations per minute that one feels when touching the artery. In this experiment, the pulse rate was measured at the wrist(!!_) Mean arteriole pressure (MAP), the value used for comparison in this lab because aortic pressure fluctuates with each heartbeat, is the pressure that sends the blood out into the tissue (Marieb and Hoehn, 702, 2012). MAP is calculated using the equation: MAP = diastolic pressure + (pulse pressure/3). Since diastole typically extends for a slightly longer period of time than systole, MAP cannot be simply the halfway point between systolic and diastolic pressures (Marieb and Hoehn, 702, 2012). Changes in blood pressure are detected by baroreceptors, also referred to as pressoreceptors, and chemoreceptors, which are receptors found in the aorta and carotid arteries. Baroreceptors detect pressure, as in the case of increased blood pressure, or lack of pressure, as in a decreased blood pressure, in the vessel and send a signal via the glossopharyngeal and vagus nerves to the medulla oblongata which then activates the cardioinhibitory center or the cardioacceleratory center. The signal then travels through the vagus nerve to the sinoatrial node in the right atrium of the heart, which then transfers the signal through the heart. Chemoreceptors, located in aorta and carotid arteries as well, detect changes in pO_2_ and pH. These are stimulated by the sympathetic nervous system (SNS) activation which causes the release of epinephrine and norepinephrine, and the parasympathetic nervous system (PNS) activation, which causes the release of acetylcholine (ACH). This lab demonstrates the effects of the SNS by stimulating stress, as when spelling, and physical activity. It measures the amount of time that the body takes to activate the PNS and decrease blood pressure and heart rate. It also demonstrates the effects of posture on blood pressure and heart rate, and how changing posture suddenly, such as going from a prone to upright position, affects these. Results: Table 1: Effect of Postural Changes Subject 1 Blood Pressure Sitting Quietly (baseline) Reclining (after 2-3 minutes) Immediately Upon Standing After Standing for 3 minutes Pulse Rate MAP 100/70 84 bpm 80 90/60 60 bpm 70 86/60 92 bpm 68.7 90/70 72 bpm 80 The subject’s blood pressure and pulse rate were first measured after having sat quietly for a few minutes to ensure relaxation, to establish a baseline, to compare further data to. The baseline systolic pressure was slightly elevated, while the baseline diastolic pressure was slightly below normal, but still well within healthy range. The baseline pulse is on the higher range of normal, but as the normal blood pressure range is 75 to 85 beats per minute, it is still within normal. Upon reclining for 2 to 3 minutes, the subject’s blood pressure and pulse rate can be expected to decrease, due to relaxation and the consequent effects of the PNS, which will result in a decrease in resistance, which in turn lowers blood pressure and heart rate (‘Human physiology in space’ 2013). One error that occurred in this stage of the experiment was that the subject, while partially relaxed, didn’t relax completely. The effects of the sudden change to standing was expected to increase blood pressure and pulse rate, partially because the heart has to increase the stroke volume in order to pump blood to muscles that have suddenly had to exert themselves, but also because peripheral resistance has increased. MAP has decreased because the heart had adjusted its force to the decrease in resistance. It required less force to reach body tissues in a prone position, and now that the body has returned to an upright position, it has not finished adjusting itself to reach the areas of the body that require more blood supply now that the muscles of posture and legs are being used. The subject also exhibits a small amount of orthostatic hypotension, which is a decrease in blood pressure immediately upon standing, caused by the pooling of blood in the legs due to gravity, which will decrease the venous return, until the baroreceptors signal the heart to adjust (‘Mayoclinic’ 2011). After standing for 3 minutes, the body has adjusted to being in the upright position again. The pulse rate, while still slightly low, which could be because although the subject is standing upright, she is still more relaxed than she was when the baseline was measured, has decreased, and the blood pressure has increased to allow for the use of postural muscles and to overcome increased resistance, due to gravity. MAP has increased to supply the increased amount of tissues being used with adequate blood supply. Table 2: Exercise Subject 1: Poorly conditioned subject Subject 2: Well-conditioned subject Well Conditioned Subject Poorly Conditioned subject Baseline Immediately 1 Minute 2 Minutes 3 Minutes 4 Minutes 5 Minutes BP: 117/68 HR: 84 MAP: 80 BP: 100/70 HR: 84 MAP: 80 BP: 118/69 HR: 76 MAP: 92.3 BP: 104/72 HR: 88 MAP: 82.7 BP: 116/69 HR: 80 MAP: 95.3 BP: 90/66 HR: 100 MAP: 74 BP: 117/72 HR: 76 MAP: 87 BP: 84/62 HR: 108 MAP: 69.3 BP: 117/68 HR: 76 MAP: 84.3 BP: 82/60 HR: 72 MAP:67.3 BP: 117/66 HR: 76 MAP: 83 BP: 80/60 HR: 72 MAP: 66.7 BP: 123/75 HR: 76 MAP: 91 BP: 120/78 HR: 160 MAP: 92