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Circulatory Lab

An Examination of Blood Pressure and Pulse of Humans and Metabolic Activity in Ectothermic Animals

Using a digital sphygmomanometer, we measured blood pressure and pulse standing and reclining and after exercise. We hypothesized that pulse goes up after exercise and that the blood pressure rises when standing. The data affirmed our first hypothesis and suggests that the second hypothesis is true. Regarding ectothermic animals whose metabolisms are affected by the environment's temperature, we hypothesized that the metabolic rate would double for each 10 °C increase. The experiment could not be performed so some data was provided by our lab instructor.


The circulatory system provides the body with transportation of wastes, nutrients, and gases. To that end, the heart pumps blood which then transports materials around the body. Pulse rate and blood pressure determine how many times the heart pumps and how hard it is pumping. Our investigation would examine the relationship between blood pressure and pulse during various activities.

As humans become more active, the circulatory system must deliver more oxygen and nutrients, remove more carbon dioxide and wastes. It can be hypothesized that the pulse will go up to provide more of the needed substances.

Standing up puts additional pressure on the heart because it must force blood up to the head. Gravity works against the heart forcing it to work harder. We thus made our second hypothesis that standing would increase blood pressure.

The ectothermic animal has a metabolism that depends on the outside temperature. The heart is part of that metabolic system and thus will slow down as the temperature drops. The quantity Q10 = 2 describes the doubling of the metabolic rate with every 10°C increase. Our hypothesis states that an ectothermic animal will double its metabolic rate with every 10°C increase.


Our investigation utilized a sphygmomanometer to measure blood pressure. The device works by collapsing the artery in the arm via a pressurized cuff. As the pressure decreases in the cuff, the blood pressure, in the artery, can start to open the artery. This opening causes sounds to be heard on the arm below the cuff. Because of the heart's rhythmic pulses, the artery, for a time, will only open with the left ventricle's contraction. The pressure exerted by the left ventricle's contraction is called systolic. As the cuff further decreases in pressure, the artery will finally return to its original shape because the "static" blood pressure equals or exceeds the cuff pressure. The "static" blood pressure is called diastolic. By monitoring when the sounds in the artery start and stop as the pressure in the cuff is released, the systolic and diastolic pressures can be determined. The sounds collectively are called Korotkoff.

The device normally consists of a column of mercury, a cuff, a pump with a release valve, and a stethoscope. Since the traditional sphygmomanometer makes it particularly difficult to hear the sounds of the artery opening, our class used digital ones.

The investigation coupled the variations in blood pressure and pulse to cardiac fitness. We measured blood pressure reclining then immediate upon standing. also we measured static standing pulse, reclining pulse, and pulse immediately upon standing, called baroreceptor reflex. Also the pulse rate after exercise was recorded. These pulses and blood pressures were then converted using the tables in the lab manual to a cardiac fitness number.

The ectothermic animal suggested by the lab manual is the Daphnia. However, our lab instructor, based on past experience with these water fleas suggested a tape of cricket chirping. But the unfortunately, that tape could not be found. The data below represents the imagination of our lab instructor and should not be construed as empirical data.

The methods involving the daphnia require the use of a microscope to count the beats of the heart and a temperature bath. By taking repeated readings, we could find the quantity Q10. In the case with the crickets, the chirping serves as the beating of the heart and can give us a rough estimate of the metabolic activity.


The absolute times used during the post-exercise pulses are approximate. In other words, the interval might not have started exactly on the 31st second but was on the 35th second.


Temperature    Metabolic Rate        
(°C)           (chips/min.)          

5              41                    

15             19                    

25             202                   

35             281                   

Q10 = = 1.9 = , where k is the rate and t is the temperature.

Subject 1

                      Systolic       Diastolic       Pulse          
                      (mmHg)         (mmHg)          (beats/min.)   

Reclining              = 118          = 69.5          = 63.5        

Immediately Upon       = 131          = 82            = 75.5        

Standing                                              = 72.5        

Time      Beats         Pulse          
(sec)     Counted       (beats/min.)   

0-15      23            23  4 = 92     

16-30     19            19  4 = 76     

31-60     36            36  2 = 72     

61-90     37            37  2 = 74     

90-120    36            36  2 = 72     

Using the tables provided in the lab book, the scores for test 1 to 5 are 3, 3, 3, 2, 2, and 3 respectively. The total score is 16 - Good.

Subject 2

                      Systolic       Diastolic       Pulse          
                      (mmHg)         (mmHg)          (beats/min.)   

Reclining             109.5          58.5            52             

Immediately Upon                                     66             

Standing              107.5          77.5            62             

Time      Beats         Pulse          
(sec)     Counted       (beats/min.)   

0-15      19            19  4 = 76     

16-30     9             9  4 = 36      

31-60     9 (15 sec)    9  4 = 36      



Using the tables provided in the lab book, the scores for test 1 to 5b are 2, 3, 3, 2, 4, and 3 respectively. The total score is 18 - Excellent.

Results and Analysis

The data was then quantized by the tables in the lab manual allowing us to determine a qualitative condition of the cardiac fitness of the individual.

Some weird readings can be attributed to machine and random errors. In subject 2, the systolic standing reading is lower than the reclining reading. Although this effect is possible, it conflicts with accepted human physiology. It may be a simple instrument error. The low beats counted during subject 2's exercise tests could result from simple human counting errors or the inherent inaccuracy of counting the beats only during a 15 second interval. A simple error of changing from 9 to 10 beats results in a 11% error. Furthermore, the human heart is not a clock and beats somewhat chaotically within its normal rhythm; thus creating an even larger margin for error. The digital sphygmomanometer stated a 5% error margin for the pulse reading. The irregularities of the pulse still could throw off the digital reading.

The data collected is highly variable between people. Although a digital sphygmomanometer has an precision of 3 mmHg, the readings are even less accurate. The placement of the cuff especially could effect readings. Because many readings were taken, the artery and surrounding tissue may not recover from the previous reading and affect readings thereafter.

The daphnia lab is difficult and error prone because of the tiny heart whose beating can be easily missed. The cricket chirping method is also error prone because it is not known how many individuals are chirping or exactly how warm the immediate environment around the cricket is. They could be sitting on a warm decaying log while the air temperature is lower. The data is a bit weird in that the chirps per minute drops from 5°C to 15°C, an unexpected change. To determine whether the change is significant or not, we would have to have the exact methods by which the data was collected, more data, and better analytic tools than the expression for Q10 provided in the lab manual.


The data collected affirms our hypothesis that the pulse would go up upon exercise. Because of an error in the systolic reading for subject 2, we cannot conclude that standing indeed raises blood pressure, but nonetheless, we are confident that this is true and believe further testing will immediately affirm our hypothesis. The hypothesis that the Q10 value will be two for ectothermic animals was affirmed by our pseudo-data.

  1. The blood pressure changes from the reclining to standing position because the heart works at different levels in the two positions. When reclining, the heart does not have to pump the blood up the arms and to the head. Thus the heart increases the pressure of its pumping. Lying down, the heart only needs to pump the blood toward the head and does not have to work against gravity. Thus the heart pumps with less pressure.
  2. High blood pressure puts undue strain on the heart and arteries. It also puts strain on the capillaries and arterioles which would create a greater chance for hemorrhages. Because the heart works too hard, the muscle tends to wear out and could quit suddenly. Because a poorly monitored diet often leads to hypertension, it is likely that the patient also suffers from plaque build-up in the arteries.
  3. The athlete's heart is used to pumping more volume of blood per pulse, the stroke volume, than the couch potato. Because the athlete's heart can increase its stroke volume during exercise, thereby pumping more blood, it does not need to increases its pulse. Thus the heart rate can remain slower until even more oxygen is needed.
  4. Smoking can cause a rise in blood pressure because the nicotine is a stimulant. The nervous system speeds up which makes the heart beat harder and faster, building up blood pressure. The nicotine stimulates the sympathetic nervous system which normally induces the fight-or-flight response. The activation of the nerve, which sends a signal to the SA-node, the pacemaker, increases heart rate and stroke volume. Because of the added volume of blood, the blood pressure rises.

  1. Temperature affects heart rate of ectothermic organisms because of the chemical activity in the cells. As temperature decreases, the enzymes work slower. Slower working enzymes reduce metabolic activity and thus the demand for nutrients goes down and the production of wastes slows. These reductions reduce the demand on the circulatory system.
  2. An endothermic organism would begin to increase metabolic activity as the temperature dropped to maintain body heat. Heart rate may try to go up to increase circulation so that the muscles and organs can burn more food and make more heat to compensate for the chilling effect of the environment.
  3. An ectothermic organism may tend to congregate where it is warmer so it may continue to live at a semi-normal pace. It may also seek out insulative environments so that the little heat it generates can warm the environment.