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Laboratory Experiment 10: Physiology of the Circulatory System for AP Biology

By — McGraw-Hill Professional
Updated on Oct 24, 2011

This experiment discusses material from human physiology. The first part focuses on how blood pressure (BP) is measured and how various environmental changes can affect an individual's BP. The second part of the lab examines the Q10 value of a water flea—Daphnia. This statistic is a number that shows how an increase in temperature affects the metabolic activity of an organism:

For  a quick review on human physiology, refer to the following concepts:

Part 1: Blood Pressure

Blood pressure (BP) is the force that allows the circulatory system to deliver its precious cargo, oxygen and nutrients, to the tissues of the body. This experiment uses students as the test subjects and measures their BP in various situations.

Measurement 1. Take BP after the student has been lying down for 5–10 minutes. This measurement serves as a baseline to compare the effects of physical challenges on the BP of an individual.

Measurement 2. Take BP right after standing up. The expected change is that the BP will increase in an effort to overcome the force of gravity that makes the movement of blood through the circulatory system more difficult.

Measurement 3. Now the pulse rate is taken after standing for a few minutes. This is to provide a baseline to compare the effects of physical challenges on an individual's pulse.

Measurement 4. The pulse rate is taken after lying down for 5–10 minutes. The expected change here is that the pulse rate will decline when lying down just as BP does because the force of gravity has been reduced and thus less effort is required to move blood through the system.

Measurement 5. The pulse rate is taken right after standing up. As with BP, the expected change is that the pulse rate will increase on standing up, owing to gravity.

Measurement 6. The subject performs some form of exercise and then immediately measures his or her heart rate. The subject then measures his or her pulse every 30 seconds after the completion of the exercise, until the pulse has returned to the original level determined in measurement 2. The increase in exercise is expected to increase both the pulse rate and the BP of an individual because of increased oxygen demand from the tissues.

The point of the repeated pulse readings in measurement 6 is to determine the "physical fitness" of an individual. The quicker an individual's heart rate and BP return to normal, the more "fit" that individual is. Following that same logic, it takes longer for people who are in better shape to reach their maximum heart rate because their hearts are "trained" to pump out more volume per beat.

Part 2: Ectothermic Cardiovascular Physiology

An ectothermic animal is one whose basic metabolic rate increases in response to in creases in temperature. In this experiment, water fleas, Daphnia, are used to measure the effect of temperature changes on ectothermic animals. An experiment to measure this effect would require the measurement of a baseline heart rate for the animal. After this, the temperature should be raised in 5-degree increments and the heart rate recorded every 5 degrees. The expected result from an experiment such as this is that ectothermic creatures will experience an increase in heart rate as the surrounding temperature rises because their temperature rises as a result. (In contrast—an endothermic animal such as a bird, whose body temperature is relatively unaffected by external temperature, would not experience the same rise in heart rate.) From this portion of the experiment, remember that the metabolic rate of an ectotherm responds to changes in environmental temperature, whereas that of an endotherm does not change much, if at all. Also remember how you would perform an experiment to show whether an organism is responding like an ectotherm or an endotherm.

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