Question

A and B

Lab Report-Human Cardiovascular Physiology 7. The figure below is cited from a research paper (Marbbn, C&Sharma, A, 2009, The Journal of Undergraduate Biological Study) It shows the effect of heat stress on heart rate (BPM), plethysmographic pulse wave amplitude ■ ) (voltsx 10, and R-pulse interval (seconds-10) in human cardiovascular response. Significant differences at 95% were noted in all three intervals documented using Student's t-test. Values are the means of n7 determinations t standard error. Note: Significance testing was only performed on values obtained at rest versus 1 minute into recovery. 120T 110 100 70 60 50 40 30 20 10 Rest After heat exposure 1 minute into recovery 2 minute into recovery According to the figure, how heat affects hear rate, pulse amplitude, and R- pulse interval? a) Compare the effect of heat and exercising on the cardiovascular function, are they use the same mechanism? Explain the mechanism(s) b)

Answer 1

A. Due to heat, the heart rate first increases and further settles down with time due to compensation. The pulse amplitude increases immediately and decreases after that to a greater extent before coming back near to normal. However, the R-ulse interval decreases and recovers to increase with time.

B. With heating, there is increase in the conduction velocity of impulses across the heart. This causes increase in heart rate. With exercise there is increased requirement of oxygen in tissues which lead to feedback increase in heart rate due to physiological needs by increasing the blood supply to the heart and is a normal mechanism The effect of exercise depends on the baroreceptor and chemoreceptor reflex that detect pressure and nutrient concentration in the blood and maintain the heart rate accordingly. They activate the sympathetic or parasympathetic system accordingly to act upon the heart.