Lesson 6 - LAB 1 - Using Instruments to Monitor Homeostasis
Student Performance Objectives
1. Take blood pressure (BP) and pulse readings using an electronic sphygmomanometer.
2. Utilize understanding of "controlled conditions" when taking measurements.
2. Graph results of 3 days readings for BP, pulse, and respiration.
3. Discuss their results and compare them with standard values in context of a laboratory report
4. Defined the following terms: tachycardia, bradycardia, hypertension, hypotension,
hyperventilation, and hypoventilation, in the context of the homeostasis lab report.
Materials Required: Instruments - electronic arm or wrist sphygmomanometers (one for each 4 students), spirometers (one for each 4 students), tables of normal values for blood pressure, pulse, and vital capacity.
A. Measuring and recording blood pressure and pulse: Students measure and record their blood pressure (BP) and pulse using electronic sphygmomanometer.
1. Note that these electronic instruments are not as accurate as mercury sphygmomanometers.
2. Also note that when taking measurements, the arm being compressed by the cuff and one's heart should be at the same level. If you hold your arm over your head when you take the BP, the value will be inaccurately low. If you drop your arm to your side when you take the measurement, the value will be inaccurately high.
3. Note that taking a reading immediately after a previous reading may not give the same value because of inherent variation in a person's BP (and also due to inaccuracy in the instrument).
1. Baseline values - Measure BP and pulse in the left arm and then the right arm. Note and explain any differences recorded.
2. Effect of standing - measure BP and pulse while standing up and note any differences. BP rises by about 5 mm HG (5 points) when standing as a compensation against the pull of gravity on the blood. What might cause an individual's BP to drop when they stand?
3. Exercise effect and recovery - After recording a resting BP, walk briskly up and down the hall for 3 minutes and measure and record BP and pulse immediately after this activity by sitting down and doing the measurement. Measure and record BP and pulse 5 minutes later while continuing to rest. Have BP and pulse returned to the previous resting value 5 minutes after exercising? In a well-conditioned individual, BP and pulse return to the resting condition within 5-10 minutes after any degree of exercise.
B. Measuring and recording vital capacity, tidal air and respiratory rate: Students measure and record their respiratory rates using a spirometer and a clock with a second timer.
1. Baseline values -
a. Take a good look at the spirometer's scale - note that each of the closest spaced lines measures 100 milliliters or ml (note that 1000 ml = 1 liter).
b. Attach a throwaway cardboard or plastic mouthpiece to the input tube of the spirometer.
c. Turn the knurled ring on the spirometer so that the internal pointer is on zero.
d. Hold the spirometer so that it is upright and that your hand or fingers are not blocking the holes on the instrument.
e. Take a deep breath and blow through the intake port blowing at a steady rate.
(1) If you blow too gently, the spirometer will read an inaccurately low value.
(2) If you blow too hard you may also get an inaccurately low value since air will come out of your nose and not register on the instrument.
(3) Practice steadily blowing and registering, on the instrument, all the air in your lungs - you cannot measure all the air if you blow quickly for 1 second and then remove the instrument from your mouth - blow as long as required through the mouthpiece to empty your lungs of air.
2. Measuring vital capacity, at rest -
a. Take the deepest breath you can and blow it all out through the spirometer.
b. Carry out the procedure at least 3 times and take the highest reading (not the average) as your true reading. Record the measurements to the nearest 50 ml. Be sure to reset the zero point each time you take a measurement.
3. Measuring tidal air, at rest -
a. Set the pointer of the spirometer at the 1000 ml mark since there are no 100 ml markings up to that point.
b. Breath normally (at rest) 3 times, exhaling deliberately through your mouth, and then after 4th inspiration, place the spirometer intake in your mouth and exhale normally through the instrument.
c. The spirometer should only register somewhere between 50 and 200 ml. If you get more or less that this you are inaccurately measuring air flow. Try this several times and record the value you "trust" as your tidal air.
4. Measuring respiratory rate -
a. After resting a few minutes, count the number of times you exhale in one minute. Take this reading as your normal, resting respiratory rate. Do not count inhalations and exhalations - your respiratory rate will be inaccurately doubled.
5. Measuring respiratory parameters after exercise - Walk briskly in the hall for 5 minutes and then measure and record the measurements for vital capacity, tidal air, and respiratory rate. Repeat these measurements 5 minutes after exercising and while seated. How do your after-exercise values compare to resting values? Do the values return to normal resting levels after 5 minutes?
C. Comparing your values to normal values - Compare all your blood pressure, pulse, vital capacity, tidal air and respiratory rate values with normal values provided to you in tables or on the blackboard by your instructor.
1. Look up and define each of the following conditions:
D. Student Assignment:
1. Measure and record these values on 3 additional days
2. Write report graphing results and comparing result with know normal values.
a. Introduction asks "why do we use these particular measurements to assess
homeostasis?" and provides an answer for the question.
b. Methods and materials describes instrumentation and how instruments are used.
c. Results present data in graphical form.
d. Discussion compares results with normal values and discusses tachycardia,
bradycardia, hypertension, hypotension, hyperventilation and hypoventilation.
e. Bibliography lists references used, in standard format.