Cardiovascular Dynamics Laboratory Report
Justify your response. (maximum 4 line response) (5 marks) From lying to sitting to standing, the resting HR is expected to increase, which the effect is shown in the subject (lying mean value = 69. 14 bpm, sitting mean value = 78. 29 bpm and standing after 2 min = 80 bpm). From lying to sitting to standing, more blood is pulled downward by gravity to the lower part of the body, making less venous return thus lowering the stroke volume. To compensate the decrease of SV thus to maintain the cardiac output, HR increases. 3.
Are the relationships between resting values for BP while lying, sitting and standing (2-minute post-lying value) what would be expected? Justify your response. (maximum 4 line response) (5 marks) The blood pressure should gradually rise from lying to sitting to standing, which is observed in the subject (MAP of lying: 69. 5mmHg, sitting: 82. 67 mmHg and standing: 95. 33 mmHg). From lying to sitting to standing, more blood is pulled downward by gravity to the lower part of the body. To push the blood upward so as to maintain enough blood flow to the brain, blood pressure needs to increase for working against the effect of gravity. . Explain the changes observed in HR and BP during the period following the subject moving from lying to standing. (maximum 4 line response) (5 marks) When the subject moving from lying to standing, BP should drop momentarily and HR should rise. The drop in BP is due to the pooling of blood in the lower part of the body. After sensing the drop in BP, the baroreceptor increases HR by the control of SNS and PNS. Then BP should rise again as the result of increased HR. The change is not seen in the subject. It might be due to other factors like the psychological factors masking the effect, or errors in measurement. . Were the observed changes in HR when your subject was rebreathing air from a paper bag as expected? Explain your answer with reference to what was expected and why. (maximum 4 line response)(5 marks) The rise in HR is expected when the subject is rebreathing air. The expectation is due to the increased CO2 concentration in the expired air will increase the blood PCO2, which be noticed by the chemoreceptors in carotid and aortic bodies. The receptors will then relay the information to CNS and indirectly leads to the increase in HR by autonomic nervous system.
But the effect is not observed in the subject. 6. What is the human diving response? Did your subject show the diving response? (maximum 4 line response)(5 marks) Human diving response is the increase in MAP and decrease in HR as a result of breath holding and the reflex after the face touched water. This is done by the increased parasympathetic activities to the heart pacemaker cells (lower HR), increased sympathetic activities to limbs leading to vasoconstriction in the limbs (increase MAP). The subject showed the diving response, as there is a egative change in HR and a positive change in MAP 30s after immersion List of references used 1. http://ep. physoc. org/content/23/1/1. full. pdf+html 2. http://www. livestrong. com/article/307646-posture-heart-rate/ 3. http://www. livestrong. com/article/268891-heart-rate-body-positions/ 4. http://www. livestrong. com/article/299614-blood-pressure-supine-vs-standing/ 5. http://en. wikipedia. org/wiki/Aortic_body 6. http://en. wikipedia. org/wiki/Cartoid_body 7. http://www. mendeley. com/research/mechanism-human-diving-response/