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Biology Lab: Capillary circulation.

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Lab Exercise

Biology Lab: Circulation System Investigations

Concepts: Blood pressure can be used as to measure of circulation health, and circulation of blood in a closed system can be observed in the capillaries.

AP Exam preparation -- Doing the AP version of this lab:

The 2009 Scholars Online Biology syllabus included a lab in circulatory physiology. While the new curriculum to some extent de-emphasizes human biology in favor of more general theoretical information, we will still perform a modified version of both parts of the original lab. It is worth looking at the AP Lab as designed, so review the laboratory setup carefully.

Goal: Part A — Blood Pressure Measurements

Materials and Equipment:


  1. If you use a sphygmomanometer or other personal device, follow the manufacturer's instructions for measuring your blood pressure. If you use a publicly available device, follow the instructions on the device.
  2. Take your pulse measurement, counting pulse beats for 20 seconds. Multiply by 3 to get pulse per minute.
  3. Take your blood pressure and record your diastolic and systolic pressure.
  4. Repeat pulse and blood pressure measurements at least twice (three total sets of data).
  5. Trial #4: Lie down if possible for at least five minutes, then repeat the pulse and blood pressure measurements, if possible, while still lying down. If you must move to the device, minimize the effort as much as possible.
  6. Trial #5: Lie down for two minutes, then stand up quickly and immediately repeat the blood pressure measurements and pulse.
  7. Pulse Rate determinations only. You will not need blood pressure measurements for this part of the lab, and may, if necessary, perform it at another time from the foregoing part.
    1. Stand quietly for two minutes, then take your pulse, counting beats for 30 seconds and multiplying by 2 to get beats per minute. Record this as your standing rate pulse. Using the following chart, determine your fitness points for standing pulse:
      Beats per minutePoints
      over 131-1
    2. Lie down for five minutes, then take your pulse, counting beats for 30 seconds and multiplying by 2 to get beats per minute. Record this as your resting rate pulse.
      Beats per minutePoints
    3. Stand quickly, determine your pulse and record this as your "baroreceptor reflex" or reclining-to-standing pulse. Determine the pulse increase from reclining to baroreceptor as the difference between the two pulse rates.
      Reclining beats per minuteIncrease in Rate
    4. Find a step at least 12 inches high. Starting with both feet on the ground, perform a step exercise: (right foot up, left foot up (so both feet are together on the step), right foot down, left foot down (so both feet are together again on the ground, repeating this five times. Take your pulse for 15 second intervals for 2 minutes following the exercise, and record number of beats per interval, e.g.: beats in the 0-15 second interval, beats in the 16-30 second interval, etc. Note the point at which the pulse returns to standing rate. Use the last two rows if your pulse is still above standing rate after 2 minutes.
      Time required to return to standing rate (seconds)Points
      1-10 beats above standing rate0
      11-30 beats above standing rate-1

      Standing beats per minuteIncrease in Rate after Exercise

Lab Report:

Create a table for your data:

Goal: Part B — Direct observation of circulation

Goal: to observe the movement of blood through capillaries as a function of temperature




  1. Measure the water temperature in which the fish has been swimming for at least 10 minutes.
  2. Remove the fish from the water and wrap the goldfish in wet cotton, except for the tail.
  3. Place the goldfish in the shallow dish.
  4. Spread out the tail so that it lies flat and put the microscope slide carefully over it.
  5. Count the pulse for 10 seconds and multiply by 6 to determine the heart rate; record this value along with the temperature.
  6. Observe the movement of the blood through the vessels of the tail. If possible, draw what you see, and record any interesting things you observe.
  7. Be sure to keep the cotton wet with the eyedropper while you make your observations.
  8. Return the fish to the aquarium water, and add ice a little at a time until the water temperature is about 5 °C lower than it was before.
  9. Soak your cotton in the colder water, then remove the fish and repeat your observations while the fish is at the colder temperature. Record the heart rate and temperature.
  10. Repeat, adding ice and taking temperatures at 5 °C intervals, but keep the water temperature above 5 °C (do not freeze the fish!)
  11. Do not keep the fish out of water for more than 5 minutes at a time, or it will die.

Lab Report:

Write a short description of your observations. Can you see individual blood cells moving through the capillaries? Do the capillaries of the tail expand and contract?

Using the formula Q10 = rate at higher temperature/rate at lower temperature, determine the ratio of heart rates at the different temperatures.