Biology Hour____ Name_________________________________
Dr. Wexler
Lab: Factors Affecting Heart Rate and Blood Pressure
5/29/09

BACKGROUND:

Heart rate and blood pressure are important indicators of cardiovascular health. They are also very simple to measure. Therefore, almost every time you visit your health care practitioner, they will measure your resting heart rate and blood pressure.

Heart rate is the rate at which your heart muscles contract and is usually measured in beats per minute (bpm). Normal resting heart rate for a young adult is anywhere between 60 and 100 bpm.

Blood pressure is the force created by the heart as it pushes blood into the arteries through the circulatory system. It is usually measured in units of mm Hg (millimeters of mercury). It is usually written as a ratio of two numbers, such as 120/75 mm Hg.

Systolic blood pressure describes the surge of pressure in the arteries as the heart beats and pumps blood out of the ventricle. It is the upper number in the measurement of a person's blood pressure. For example, in the measurement 120/75, 120 is the systolic blood pressure.

Diastolic blood pressure is the pressure in the arteries when the heart relaxes between beats. It is the lower number in the measurement of a person's blood pressure. For example, in the measurement 120/75, 75 is the diastolic blood pressure.

Normal blood pressure is variable based on gender, age, and physical condition. In general, however, systolic blood pressure higher that 140 mm Hg and/or diastolic blood pressure higher that 90 mm Hg is considered above normal. Systolic blood pressure below 100 mm Hg is generally considered below normal. Many factors may affect heart rate and blood pressure -- physical activity, emotional state, time of day, temperature, drugs, body posture, etc.





Step One: Develop a hypothesis for the team members to test

Choose a parameter to test. For example, “Our hypothesis is that standing up causes a reduction in systolic blood pressure compared with lying down", or "Our hypothesis is that lying down causes a reduction in diastolic blood pressure compared with standing up", or "Our hypothesis is that lying down causes a decrease in heart rate", or "Our hypothesis is that lifting a heavy weight causes an increase in systolic and diastolic blood pressure", or "Our hypothesis is that vigorous exercise causes an increase in systolic blood pressure", or "Holding my breath causes an increase in heart rate", etc.

Decide how you will test your hypotheses. Design a simple experiment using any of the available materials/facilities. You will want to replicate the experiment for each member of your group. Make sure that each person experiences the factor you are testing in the same way. For example, if you are testing the effect of exercise, each person should do the same kind of exercise, with the same intensity, for the same amount of time. You will also need a control. For this experiment, you can measure each person’s resting heart rate before the experiment and then immediately after they are exposed to the factor you are testing. The resting heart rate before the experiment is the control.

Describe your experimental procedure:

 

 

 

 

 

 

 

What is the independent variable?

 



What is the dependent variable?

 

 

 







Step Two: Collect data.

Carry out your experiment, and record your raw data in table format.


Example:

Before exercise After exercise
Heart rate Diastolic Systolic Heart rate Diastolic Systolic
Student X
Student Y
Student Z

 
Step Three: Analyze your results and draw conclusions.

  1. Calculate the average heart rate of people in your group before exposure to the experimental factor and after.

Average heart rate before: _____________ bpm

Average heart rate after: _____________ bpm

Average difference in heart rate before and after:___________bpm

  1. Calculate the average diastolic blood pressure of people in your group before exposure to the experimental factor and after.

Average diastolic blood pressure before: _____________ mm Hg

Average diastolic blood pressure after: _____________ mm Hg

Average difference in diastolic blood pressure before and after:___________ mm Hg

  1. Calculate the average systolic blood pressure of people in your group before exposure to the experimental factor and after.

Average systolic blood pressure before: _____________ mm Hg

Average systolic blood pressure after: _____________ mm Hg

Average difference in systolic blood pressure before and after:___________ mm Hg

 

  1. Did the average heart rate, go up or down after exposure to the experimental factor?

 

  1. Were there individuals for whom the difference in heart rate before and after was in the opposite direction from the average difference? What explanation can you think of for this result?

 

  1. Did some individuals' heart rate change a lot, while others changed only somewhat? What explanation can you think of for this result?

 

  1. Did the average diastolic blood pressure go up or down after exposure to the experimental factor?

 

  1. Did the average systolic blood pressure go up or down after exposure to the experimental factor?

 

  1. Were the changes in average systolic and diastolic blood pressure roughly the same or different? What explanation can you think of for this result?

 

  1. Did the data support your hypothesis or falsify it?

 

  1. What can you conclude about the effect of the factor you chose on heart rate and blood pressure?









  1. Are there any changes you might want to make to your experimental design if you were to do it again?







 

  1. What further questions might you explore with other experiments if you had the time?