The Campus Coffee Shop by Heck, Novicki and Rybarczyk
Part IV—Caffeine and the Cardiovascular System
“I tried drinking hot coffee once and my heart started beating faster and I felt energized, almost overstimulated. I stay away from the stuff. I asked my doctor about it and he said something about vasoconstriction,” Sally said.
“How about we do a little experiment and measure our blood pressures when we drink caffeine and include real data as part of our biology project,” proposed Jenna.
Alex exclaimed, “Hey, I found these equations… maybe we can use these to explain what’s going on when we drink caffeine…”
- Mean Arteriole Pressure (MAP) = cardiac output X total peripheral resistance
- cardiac output = heart rate X stroke volume
- MAP = 1/3(systolic) + 2/3(diastolic)
- Using the students as subjects, design an experiment that will help them determine the effects of caffeine on MAP over time. Predict the results for each student. Use the equations above to help explain the results.
- What is vasoconstriction? If vasoconstriction is a result of caffeine signaling, describe the changes that would occur in MAP.
- What is an average MAP reading? Calculate Jenna’s and Sally’s MAP (at rest and with caffeine) using the systolic and diastolic readings provided in the tables below.
| Jenna |
epinephrine levels | blood pressure |
| resting | 290 pg/mL | 120/80 |
| with caffeine | 291 pg/mL | 120/81 |
|
|
| Sally |
epinephrine levels | blood pressure |
| resting | 292 pg/mL | 113/75 |
| with caffeine | 290 pg/mL | 130/95 |
|
- Propose biological and physiological differences between Jenna’s heart rate and Sally’s to help explain the data above.
- Give examples of common catecholamines and describe how they work. If Sally was given a beta-blocker, what would you predict would happen to her heart rate? Why? What about for Jenna?
- If catecholamines are involved in increasing heart rate, how do you explain the data in the chart provided? What alternative biological/molecular/cellular explanations can you provide to explain the data?
- If hypertension is characterized by beta-receptor down-regulation, what will happen if someone who has hypertension consumes caffeine?
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