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Diurnal Blood Pressure Variation

Experiment #9 from Human Physiology with Vernier

Education Level
High School


Blood pressure is determined by the output of the heart and the resistance to flow in the vascular system. These, in turn, are affected by factors such as the levels of certain hormones (renin, angiotensin II, aldosterone, cortisol, epinephrine, and norepinephrine), physical activity, emotional or physical stress, salt intake, and smoking. Blood pressure usually reaches a high at 6 a.m. and a low between 2 and 4 a.m. Small peaks and valleys occur every one to two hours throughout the day. For this reason, health care providers measure blood pressure at random times on multiple occasions before diagnosing hypertension, or elevated blood pressure.


In this experiment, you will

  • Obtain graphical representation of blood pressure measured at different times of the day.
  • Analyze the variability of blood pressure readings individually and as a class.
  • Correlate your findings with variables that may have influenced your blood pressure.

Sensors and Equipment

This experiment features the following sensors and equipment. Additional equipment may be required.

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This experiment is #9 of Human Physiology with Vernier. The experiment in the book includes student instructions as well as instructor information for set up, helpful hints, and sample graphs and data.

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