Activity 8.1.2 Vital Signs: Heart Rate and Blood Pressure Introduction The human body is an amazing machine that automatically monitors and adjusts itself in order to maintain equilibrium or homeostasis. The body sweats to keep cool and shivers to stay warm; this is an example of maintaining homeostasis. All of the body s systems work together to maintain balance; two of the most important systems for maintaining homeostasis are the nervous and endocrine systems. The endocrine system is a system of glands that secrete different hormones into the bloodstream. The nervous system helps regulate breathing and heart rate. As you discovered in the previous activity, vital signs are measurements of the body s most basic functions and are useful in detecting or monitoring medical problems. The four main vital signs include body temperature, pulse rate, respiration rate, and blood pressure. You probably have your vital signs measured when you visit the doctor or other medical professional. The values of your vital signs act as clues that can be used to diagnose an illness or disease. Two vital signs that relate to the heart are heart rate and blood pressure. Normal heart rate for a teen or adult is between 60-100 beats per minute. Younger children have a higher normal heart rate, while well-conditioned athletes have a lower normal heart rate. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps blood. The pressure is determined by the amount of force applied by the heart and the quantity of blood being pumped. Extended periods of high blood pressure can damage the heart, blood vessels, kidneys, and other vital organs in the body. Blood pressure is not constant. It is lower when you sleep and can rise when you are excited, nervous, or active. Normal blood pressure for a healthy adult is less than 120/80. This means the pressure on the arteries when the heart is contracting, also called the systolic reading, is less than 120 mmhg. Likewise the pressure on the arteries when the heart is at rest, or diastolic reading, is less than 80 mmhg. The units for blood pressure are millimeters of mercury (mmhg), the same unit used to measure atmospheric pressure. In this activity you will measure your heart rate and blood pressure and calculate average readings for your team. You will also use an interactive website to maintain homeostasis in a virtual body. PLTW Gateway Medical Detectives Activity 8.1.2a Vital Signs: Heart Rate and Blood Pressure Page 1
Equipment Laboratory journal Pencil Stopwatch or clock with a second hand Automatic blood pressure device Procedure 1. View the following movie introducing the cardiovascular system. Your teacher may choose to show this to the entire class. http://kidshealth.org/kid/closet/movies/csmovie.html?tracking=85031_a 2. Measure your pulse and record the value on the data table. a. Place two fingers from your right hand on the inside of your left wrist. Do not use your thumb as it has a faint pulse and may change your reading. b. Use a stopwatch or clock with a second hand and count the number of beats you feel for 10 seconds. c. Multiply that number by 6 and record below. This is the beats per minute, or. d. Record the data for your teammates and find the average. Student Name Heart rate Team Average 3. To find blood pressure, your team will use the automatic blood pressure device. This device will also measure heart rate, or pulse in beats per minute. 4. Measure your blood pressure and record the value on the data table. a. Place the cuff on your left arm, taking care to line up the arrow indicating the artery with the inside of your elbow. The tubes should be running down toward your hand. b. Tighten the cuff around your upper arm so it does not slide around but not so tight that it is uncomfortable. PLTW Gateway Medical Detectives Activity 8.1.2a Vital Signs: Heart Rate and Blood Pressure Page 2
c. Press the Start button on the monitor and keep your arm and hand still and relaxed. Allow the machine to tighten and relax. d. Record your reading on the data table below. e. Record the readings for your teammates and calculate the averages. Student Name Blood pressure Heart rate Team Average 5. When you finish measuring your blood pressure or while you are waiting for the equipment, visit this website http://kidshealth.org/teen/diseases_conditions/heart/hypertension.html and answer conclusion questions 1-5. Visit this website http://vitalny.pbslearningmedia.org/resource/tdc02.sci.life.reg.bodycontrol/bodycontrol-center/ and answer conclusion questions 6-8. 6. Answer the remaining conclusion questions. PLTW Gateway Medical Detectives Activity 8.1.2a Vital Signs: Heart Rate and Blood Pressure Page 3
Conclusion 1. What factors can affect blood pressure? 2. In this lab you used a machine to measure blood pressure. What other two instruments are used to measure blood pressure? 3. What is hypertension? 4. What causes hypertension? 5. List three ways you can prevent hypertension. 6. Which body system keeps your body in equilibrium or homeostasis? 7. List three examples of daily activities that affect homeostasis. 8. List the five body functions that monitor homeostasis. 9. What are the units used to measure heart rate? 10. What are the units used to measure blood pressure? PLTW Gateway Medical Detectives Activity 8.1.2a Vital Signs: Heart Rate and Blood Pressure Page 4
11. What is the name for the top number in blood pressure? Is this the pressure when the heart is contracting or relaxing? 12. Was your pulse the same as measured by you and the blood pressure cuff? If not, why do you think these values were different? 13. Why is it important to keep your body in equilibrium or homeostasis? PLTW Gateway Medical Detectives Activity 8.1.2a Vital Signs: Heart Rate and Blood Pressure Page 5