When a person encounters a sudden or life threatening situation, their body reacts with the fight or flight response. During the fight or flight response, adrenaline is released into the bloodstream from the adrenal glands. This causes nonessential blood vessels to contract. These include blood vessels going to the urinary and digestive systems as well as those near the surface of the skin. However, blood vessels going to the brain, lungs, and muscles dilate, allowing more blood to get to these parts of the body.In a previous lab, it was learned that the fight or flight response causes heart rate to increase when a subject’s feet are submerged in ice water. The heart rate increases because more oxygen is needed in the muscles and the only way to supply more oxygen is for the heart to beat faster.
Blood pressure is the force exerted on the arterial walls by the blood. Systolic pressure occurs during ventricular contraction when blood is pumped out of the heart. Diastolic pressure occurs between contractions when blood is not moving. A blood pressure reading is given as systolic over diastolic. By performing this experiment, the goal is to determine whether or not the fight or flight response, simulated by placing a subject’s feet in ice water, causes blood pressure to increase or decrease.
The blood pressure of the test subject will be higher after the feet have been submerged in ice water than it was before the feet were submerged in ice water.
Computer with Vernier Logger Pro software
Vernier LabQuest Mini with USB cable
Vernier blood pressure cuff
Ice water bath
Experimental Design Resource Sheet
How to Write a Scientific Laboratory Report Resource Sheet
Procedure (Partially adapted from PLTW PBS Activity 2.3.2)
Start the Logger Pro software and open the Blood Pressure program.
Click on File Open and open the Human Physiology with Vernier folder.
Open the program titled 07 Blood Press Vital Sign.
Connect the LabQuest Mini to the computer using the USB cable.
Connect the Blood Pressure Sensor into CH 1 of the LabQuest Mini.
Wrap the blood pressure cuff around test subject’s upper arm. Be sure to secure the cuff around the arm very snugly. Also make sure that the arrow on the cuff is pointing toward the test subject’s index finger and that the tubes run down the inside of the test subject’s elbow. Do not inflate the cuff yet.
Position the test subject so that he or she is seated with an arm resting on the table. While taking the blood pressure measurement is being taken, the test subject should remain seated and not move.
Hit the green Collect arrow in the top of the toolbar.
Pump up the cuff using the rubber bulb until the cuff pressure gauge reaches 150 mmHg.
Stop pumping and allow the cuff to gradually lose pressure.
Wait until the cuff pressure reaches 50 mmHg and then hit the red stop button.
Release the pressure valve but do not remove the cuff.
Under the Experiment menu, select Store Latest Run.
Record the Systolic, Diastolic, and Mean Arterial Pressures in the Laboratory Journal. Record the data as Run 1.
Wait 3 minutes before starting the next run.
While waiting fill a tub with 3 cups of ice and half way with cold water.
The same subject now places both of their bare feet into the tub so that they are both submerged
The subject now keeps their feet in the ice water for 1 minute.
After a minute, wrap the blood pressure cuff snugly around the test subject’s arm.
Hit the green Collect arrow.
Pump up the cuff to 150 mmHg.
Stop pumping and let the cuff gradually lose pressure.
When the cuff pressure reaches 50 mmHg, hit the red stop button.
Release the remaining cuff pressure by pressing the release valve.
Remove the cuff from the test subject’s arm.
Under the Experiment menu, select Store Latest Run.
Record the Systolic, Diastolic, and Mean Arterial Pressures in the Laboratory Journal as Run 2.
After completing the control and ice water runs for the experiment, there appears to be a change in blood pressure. In the control run, the test subject had a systolic pressure of 100 mmHg, a diastolic pressure of 57 mmHg, and a mean arterial pressure of 75 mmHg. After subjecting the test subject’s feet to an ice water bath blood pressure was taken, the test subject had a systolic pressure of 119 mmHg, a diastolic pressure of 53 mmHg, and a mean arterial pressure of 80 mmHg. In summary, systolic pressure increased by 19 mmHg, diastolic pressure decreased by 4 mmHg and mean arterial pressure increased by 5 mmHg. The graphs reflect the previously mentioned data.
Control and Ice Water
The first thing that can be interpreted from the data is that the test subject has lower than average blood pressure. This is apparent because the control blood pressure was 100/57 and an average blood pressure is 120/80. It is normal for the diastolic pressure to decrease slightly so this was not an error. However, it is not supported by the hypothesis. The systolic pressure measurement after ice water exposure was 19 mmHg higher than the control; this supports the hypothesis. The mean arterial pressure was 5 mmHg higher than the control. This is also supported by the hypothesis. The mean arterial pressure increased because the heart was pumping faster in order to get more blood to the lungs, muscles and brain. This supports what was said in the background.
There were some factors that may have caused errors in data during the experiment. The blood pressure cuff was pumped past 150 mmHg for both runs. This may have skewed the readings. Another factor that may have contributed to error was that the ice water run had to be redone twice because of operator error when the cuff was being inflated. This may have caused the test subject to adapt to the ice water. The experiment was conducted in a room with other people talking and moving around, which may have affected the nervousness of the test subject. Other electronic devices around the equipment may have interfered with the readings.
If the experiment was to be conducted again, it should be done in a quiet, plain white room containing only the people necessary to the experiment. Also, there should be no other electronic devices in the room other than the equipment and the blood pressure cuff should be inflated to exactly 150 mmHg.
The same test could be preformed on multiple subjects of different, races, body types, and ages to obtain results that are more average. More runs could also be done on the same subject to obtain data that is closer to their average.
The test subject’s diastolic pressure and mean arterial pressure were elevated after their feet were subjected to an ice water bath.