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Lesson 3: Under Pressure



Students will investigate the implications of blood pressure.

Key Question

  • What does blood pressure signify?

Materials For the class

  • blood pressure monitor

Materials For each student

  • one film canister with a hole in the bottom
  • balloons
  • pencil
  • paper

For the teacher only

  • drill
  • drill bit
  • block of wood

Advance Preparation

Collect empty film canisters from a local camera store. Using the drill, drill bit, and block of wood, drill a hole in the bottom of each film canister.



1. Demonstrate to the class how to use the blood pressure monitor.

2. Form partners or small groups and take turns administering and recording blood pressures for each student.

3. Record the highest number and the lowest number for each of the blood pressure measurements. Put the highest number on the paper first. Draw a line under it and put the lower number under the line. Stimulate a discussion about the activity by asking questions about what the numbers represent and what students observed during the process.

4. One of the numbers measures the pressure when the heart is contracting or beating (pumping blood) and the other number measures the pressure when the heart is at rest or between beats (filling with blood). Ask students whether they think the higher number measures the heart beating or the heart at rest.

5. The larger number or reading is called systolic, and the smaller number is called diastolic. Write these names by the numbers recorded earlier. Which is the correct word for the number of the reading when the heart is beating? Answer: Systolic. Which is the correct word for the number of the reading when the heart at rest? Answer: Diastolic.

6. Insert a film canister into the mouth of a balloon, putting the open end inside first and the end with the small hole facing out. Inflate the balloon by blowing on the end of the film canister. Lead a discussion about the impact of moving something through a smaller opening by asking questions like, Is this easier than inflating the balloon simply by blowing on the mouth of the balloon? What would happen if the heart was pumping blood through clogged vessels? Would the heart have to beat harder and faster to get the blood through the vessel? Could this cause high blood pressure?

balloon and canisterballoon and canisterballoon and canisterballoon and canisterblowing into canisterblowing into balloon


1. Research the positive and negative effects of salt on the body.

2. Look at the food labels on foods you eat for one week and record the amount of sodium per item. Total this list at the end of one week. What do you think about the amount of salt eaten during the week? Do this for the listings of fat, cholesterol, and carbohydrates. Make a list of the foods with the most sodium, fat, and cholesterol.

Notes to the teacher: Blood Pressure

Blood pressure is a measurement of the force of the blood within the vessels of the circulatory system as it moves through the passages. When the heart contracts there is a surge of blood. This is called the systolic phase and is the higher of the two numbers given in blood pressure measurement. When the heart is at rest between beats, this is the diastolic phase. The diastolic number is smaller than the systolic number. The number for the systolic phase is written over the diastolic number as a ratio, or fraction, e.g., 120/80.

Chart of Age-Appropriate Blood Pressure Ranges

Years of Age Systolic Diastolic
Birth 50-70 25-45
Neonate 60-90 20-60
(6 months)
87-105 53-66
Toddler 95-105 53-66
School age (7 years) 97-112 57-71
(15 years)
112-128 66-80
Adult (18+) 120 80

The above numbers came from Pediatric Advanced Life Support Provider Manual. The general equation that is used for figuring out if a child (aged 1-10) is at 50th percentile for bp is 90mmHG + (2 x age in years).

A blood pressure reading with a systolic measurement of 140 and a diastolic measurement of 90 is commonly stated as 140 over 90. Repeated high or low readings of one or both may indicate high or low blood pressure. This diagnosis is usually made depending on other signs and symptoms.

The blood pressure activity is intended to be educational rather than diagnostic. Obtaining a high reading is not necessarily an indication of high blood pressure. Only a health specialist should make this determination.

The causes for high blood pressure can vary and are difficult to determine. It might be from narrowing of the arteries, a greater than normal volume of blood, or the heart beating faster or more forcefully than it should. Any of these conditions will cause an increased force against the artery walls. High blood pressure can also be caused by diseases such as kidney disease.

The most important factor in preventing high blood pressure is through maintaining good health, especially with a healthy diet and exercise.

Fat does not directly affect high blood pressure but "saturated fats" in the bloodstream can raise the level of cholesterol which plays a role in heart disease. Fat is also necessary to maintain a healthy system. You need fat for insulation, nerve conduction, energy (especially young people), and as an essential nutrient in all cells. You can be "heart-smart" by eating fats in moderation and by reducing the amount of saturated fats in your diet. This can be done by reading food packages carefully, although moderation is sufficient for most people.

Web Links

Surfing Inside the Human Body

This fun and creative site has been put together by three youths through the Think Quest Internet Challenge; it is a great resource for basic information about the human body and its systems.

Sodium Savvy

Sodium Savvy
Written by Catherine A. Broihier, this article about sodium contains detailed information and fun facts about the mineral, including the effects sodium can have on the body.


Part of the Franklin Institute's online exploration of the heart, this link contains interesting information about hypertension, such as what hypertension really is, the risk factor, and ways of preventing hypertension.


Click here to see a sphygmomanometer!

Blood Type

Microsoft Encarta's online version provides a concise description of the different blood types and what the significance of each is.


| lesson 1: Pulse of Life| lesson 2: Keeps on Pumpin' | lesson 3: Under Pressure | lesson 4: Sounds of the Heart | lesson 4a: Valves and Pumps | lesson 5: Lub Dub (valves) | lesson 5a: The Heart as a Pump | lesson 6: Go With the Flow | lesson 7: Lung Model | lesson 8: Ins and Outs of Respiration | lesson 9: Catch Your Breath | lesson 10: O2 CO2 Skit | lesson 11: X-Rays |

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