Blood Pressure Activity

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					                   Blood Pressure Activity
Blood pressure is a measure of the force that blood exerts on the major arteries. The
amount of blood found in the major arteries depends on cardiac output and
resistance to the exit of blood from the arterial system. The highest blood pressure in
the arteries (systole) is caused by ventricle contraction. The lowest blood pressure
(diastole) occurs during ventricle relaxation. During the relaxation phase no blood is
entering the arteries, but blood continues to exit through the arterioles. Blood
pressure is the result of the force of pumped blood pressing against the walls of the

In this exercise, we will determine arterial blood pressure and apply measurements
of blood pressure to the study of posture. You will measure the blood pressure of
another student after setting and standing for three minutes and another student
will perform the same procedure on you.

Watch or clock with a second hand

Determination of blood pressure.

Arterial blood pressure is determined by an indirect method in this laboratory. The
sphygmomanometer is an inflatable tourniquet that, when wrapped around the arm
and inflated, increases the blood pressure on surface arteries, thereby occluding
them. When the artery is occluded, no pulse can be heard beyond the tourniquet.

1. Have the subject expose one arm well above the elbow. The subject should be
   seated, with the arm slightly flexed.

2. Wrap the cuff of the sphygmomanometer around the subject’s arm, at least 5 cm
   above the elbow.

3. Close the valve of the rubber bulb, and inflate by squeezing the bulb until a
   pressure of 180 mm Hg registers on the sphygmomanometer.

                   DO NOT Exceed a pressure of 180 mm Hg!!
               DO NOT cut off circulation for longer than 1 minute!

   Should the reading be unsuccessful, change arms and try again.

4. Place the stethoscope bell, or diaphragm, on the inside of the arm immediately
   below the cuff.

       This activity meets the following DoE Specific Curriculum Outcomes for Biology 11: 212-6, 213-5 and 214-9.
5. Slowly release the valve on the rubber ball and listen for a sound. The sound is
   caused by blood running through the partly constricted artery
   a) Record the pressure indicated by the sphygmomanometer after the first sound
      has been heard.

6. Slowly reduce the pressure another 10 mm Hg while listening to the brachial
   b) Does the sound increase in volume or decrease? Provide an explanation.

7. Continue deflating the cuff until all sounds disappear. (It should be noted that
   many authorities insist that the muffled sound. heard just before the cessation of
   sound in the artery is a measure of diastolic blood pressure).
   c) Record the pressure indicated by the sphygmomanometer immediately after all
      sound has disappeared.

8. Release the pressure by turning the valve on the bulb to open, and remove & the

9. Change subjects so that each person in the group has the opportunity to have his
   or her blood pressure taken, as well as to determine someone else’s blood
   d) Compare your blood pressure to that of another member of your lab group. Blood
      pressure is recorded as systolic valve  diastofic valve.

Complete this procedure for both sitting and standing postures.

                             Lying down                                  Standing
                             (3 minutes)                                 (3 minutes)
Blood Pressure
blood Pressure


1. Blood pressure taken by the method above registered a pressure of 120/80. Does
   this mean that the pressure in each of the major arteries is 120mm Hg during
   ventricle contraction? Explain why or why not.

2. The blood pressure in adults is usually greater than the blood pressure in
   children. Indicate why.

3. Explain why the highest blood pressure is recorded when you are standing.

4. Many times when you get up too quickly you feel dizzy What is your explanation
   for this feeling.

5. Arteriosclerosis, or hardening of the arteries, causes a rise in blood pressure
   Explain why this occurs.

6. Pilots during World War II would often black out after pulling out of a dive. This
   accounted for the death of many pilots prior to the invention of pressurized
   cockpits. Provide a physiological explanation for black-outs.

       This activity meets the following DoE Specific Curriculum Outcomes for Biology 11: 212-6, 213-5 and 214-9.

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