HEART, BLOOD VESSELS & FITNESS Biology 119 Heart & Artery Anatomy The heart is enveloped in a two-layered sac or pericardium. The inner visceral pericardium or epicardium is on the surface of the heart. The parietal pericardium forms a container for the heart. The outer surface of the parietal pericardium is tough fibrous material and very fatty. Both layers secrete a serous fluid that allows the heart to move in the sac without creating friction. The heart itself is composed of an inner layer of simple squamous epithelium called endocardium. This forms a smooth surface to aid blood flow and reduce the risk of clot formation. The endocardium is continuous with the inner lining of the blood vessel endothelium. Most of the heart is made of cardiac muscle tissue called the myocardium. The interior of the heart is divided into right and left sides and has a total of four chambers. The right and left atria receive venous blood and pump blood into the ventricles. The walls of the atria are very thin because these chambers only need to pump into relaxed, and partly empty ventricles. The larger right and left ventricles move blood out of the heart into the arteries & must generate enough force to move the blood through the cardiovascular circuits. The left ventricle has the thickest walls because it pumps into the longer, high-pressure systemic circuit. The right ventricle is not as strong because it must pump blood only through the shorter, low-pressure pulmonary circuit. The heart has a series of valves that control the direction of blood flow through the heart. These valves are normally smooth and very flexible. They are made of dense connective tissue and are covered with endocardium. When the atria pump blood into the ventricles, blood flows over atrioventricular or AV valves. The right AV valve is also known as the tricuspid valve because it has three flaps. The left AV valve is known as the mitral or bicuspid valve and has only two flaps. When the ventricles contract, the AV valves are closed with such tremendous force that these valves might be forced open. The AV valves are held in place and kept form opening with tight cords (chordae tendinae) and papillary muscles. The blood in the ventricles is then pushed out through semilunar valves into the arteries. The semilunar valves have three crescent or half-moon shaped "pockets" that flatten when blood leaves the ventricles then the valves close and fill with blood when the ventricle relaxes. Pathways of Blood Flow Systemic Circuit = high pressure Function: oxygenated blood goes to heart muscle, brain... to give up oxygen & pick up carbon dioxide Pathway: left atrium --> left ventricle --> aorta --> systemic tissue capillaries --> vena cava Pulmonary Circuit = lower pressure Function: deoxygenated blood goes to the lung's alveoli to give up carbon dioxide & pick up oxygen Pathway: right atrium --> right ventricle --> pulmonary artery --> pulmonary capillary --> pulmonary veins Normal Large diameter vessel has a ruffled or folded endothelium that allows the arterial wall to stretch. The thick muscular walls contain elastic fibers that may be visible (stained black). Arteries can stretch as blood enters & then recoil as blood exits. Microscope Slides of Arteries Mild Atherosclerosis Only 1 section of the artery is visible. The endothelium or inner wall of the artery has a small bump into the interior lumen. The fatty plaque is a soft, spongy region with white blood cells filled with fat & an excess growth of smooth muscle cells. Severe Atherosclerosis The fractured areas are cholesterol deposits. Most of the original interior space of the artery is filled & the plaque restricts blood flow. Increased resistance & loss of elasticity raises blood pressure and also increases the risk of blood clots.
SHEEP HEART EXAMINATION Identify the structures listed in the tables below & use these orientation HINTS: Apex or tip of heart = left ventricle Arteries are on the front or ventral side of heart. Veins are on the backside of the heart & are often cut off (find the holes that remain). Layers of Heart Pericardium = Parietal Pericardium Epicardium = Visceral Pericardium Myocardium Endocardium sac encloses heart covers outer surface of heart middle layer of heart wall innermost surface of heart covers heart valves connective tissue & epithelium connective tissue & epithelium thick, cardiac muscle tissue thin, smooth, epithelium Paired (R & L) Chambers of Heart = Dual Pump Design Atria (A) small, thin walls above AV valves Ventricles (V) large, thick walls; especially left side below AV valves & semilunar valves Heart's Major Vessels Vena Cava Pulmonary Artery Pulmonary Veins Aorta deoxygenated blood deoxygenated blood oxygenated blood oxygenated blood enters - RA exits - RV enters - LA exits - LV thin, posterior surface thick, anterior surface small, usually missing largest, center & top of heart Label the chambers, blood vessels & valves of this heart diagram.
Experiments A. Heart Sounds 1. Place a stethoscope over your heart in several different positions. 2. You should be able to hear two soft tapping sounds that are called: lub - dup. 3. The first heart sound (lub) occurs when the ventricles contract (systole). 4. This sound is produced by the closure of the AV valves when blood is forced against them. 5. The second heart sound (dup) occurs when the ventricles relax (diastole). 6. This sound is produced by the closure of the semilunar valves when arterial blood pushes back against them. B. Resting Heart Rate or Pulse Rate (While standing up.) 1. Place your index finger over the radial artery in your wrist OR over the carotid artery in your neck. 2. DO NOT PRESS HARD, especially on the carotid!!! 3. The regular beating that you feel is the increase in pressure during each heart contraction. 4. Count number of pulses (beats) in a 15 second interval. 5. Multiply the number of pulses by 4 to get the total beats/min. Your 15 Second Pulse Count X 4 = Heart Beats/Minute Fitness Ranking from Table Below X 4 = Descriptive Ranking Percentile Rank Men s Pulse (beats/min.) Women s Pulse (beats/min.) superior 100 49 54 95 52 56 90 55 60 excellent 85 57 61 80 60 64 75 61 65 above average 70 63 66 65 64 68 60 65 69 average 55 67 70 50 68 72 45 69 73 below average 40 71 74 35 72 76 30 73 78 poor 25 76 80 20 79 82 15 81 84 very poor 10 84 86 5 89 90
C. Blood Pressure Blood pressure measurement is one of the most common clinical tests. Everyone over the age of 3 is recommended to get their blood pressure checked annually. The primary purpose for measuring blood pressure is to determine the potential risk of cardiovascular disease. If the pressure is high, appropriate medications and lifestyle changes are recommended. Typically the brachial artery is measured because of convenience and its position at heart level. When blood is ejected from the ventricles it exerts a pressure against the walls of the arteries. This pressure is called hydrostatic pressure. Blood pressure is determined primarily by two factors: cardiac output (CO) and peripheral resistance. Cardiac output measures the amount of blood pumped into the arteries per minute (i.e. volume). Peripheral resistance is most strongly correlated to blood vessel diameter. As blood moves toward the capillaries, the vessel diameter decreases and the resistance to blood flow increases. Blood must exert considerable force to overcome this resistance in the systemic circuit. Resistance to blood flow is normally much less in the pulmonary circuit because its shorter & the vessels usually have a larger diameter. So, the blood pressure in the pulmonary circuit is much lower than the systemic circuit. Blood pressure is related to both cardiac output (CO), the amount of blood pumped out of the heart per minute & factors affecting resistance to blood flow. Resistance to blood flow is primarily determined by vessel diameter, as the vessel is dilated (larger) the resistance to blood flow drops. This is called peripheral resistance when the resistance of the blood vessels in a circuit are summed together in an estimate of resistance along the entire pathway. Cardiac output increases as heart rate (HR) & the force of contractions increases the amount of blood pumped by the heart with each heartbeat. This is referred to as stroke volume (SV). As expected during exercise, CO increases because both HR & SV increase. Regular aerobic exercise should strengthen the heart & increase stroke volume. At rest, the cardiac output of trained individuals is the same as that of untrained individuals. Because resting CO is constant, your heart rate can decrease if you have a stronger heart. Understand the relationships shown in these equations: Blood Pressure (~ Diastolic BP) = CO * Resistance CO = Heart Rate (HR) * Stoke Volume (SV) "Peripheral" Resistance ~ 1/(vessel radius) 4 (+ other factors such as blood viscosity) BP ~ (HR * SV) * [1/(vessel radius) 4 ] The heart pumps blood intermittently. During systole (contraction) blood is thrust into the arteries, but during diastole (relaxation) no blood leaves the heart. In vessels with rigid walls the pressure would rise to very high values during systole and fall nearly to zero during diastole. However, arteries do have elastic walls. During systole, the expanding arteries store part of the blood volume so that during diastole blood is still propelled forward by the elastic recoil of the artery walls. Elastic arteries buffer changes in pressure & flow caused by the intermittent heart beat. Systolic pressure can be quite variable, it increases with increases in blood flow associated with exercise. During exercise, systolic pressure may average 200 mmhg in a young individual. If systolic BP exceeds 240 mmhg during an exercise test, it may indicate a susceptibility to hypertension. Diastolic blood pressures change less because resistance to blood flow should decrease during exercise (vessels dilate). Diastolic values taken during exercise vary from showing an increase of 3-11 mmhg above resting diastolic BP to a decrease in diastolic BP during exercise of a highly fit individual. Approximately 4% of individuals ages 18-29 have hypertension, but it increases in the population as we age. When the pressure is too low, we suffer hypotension. You heart can't deliver enough oxygen to the brain so you pass out or go into shock. If the pressure is dangerously high it is called hypertension. The artery walls & capillary walls, in particular, are under excessive strain or tension from the high pressure. Over time, this can cause arteries to "crack open". This leads to massive hemorrhaging & death in most cases. Small capillaries can rupture more easily & these ruptures may trigger heart attacks, strokes or organ damage such as kidney failure. Hypertension Hypotension Circulatory Shock >140/90 mmhg < 90/60 mmhg < 80/40 mmhg
Using Traditional Sphygmomanometer 1. Subjects should rest for at least 5 minutes prior to the measurement. 2. Place the cuff sensory region (marked with green) over the brachial artery. 3. Traditionally the right arm is preferred, but there may be no statistical difference between arms. 4. Roll up your shirt s sleeve to place the cuff on a bare arm. 5. If the rolled up sleeve fits tightly around the upper arm, the shirt/sweater should be removed. 6. The subject should be seated with the arm resting on the table. Use of Digital Arm Cuff 1. Press power button ON. 2. Three sets of symbols appear quickly in sequence a. 888 888 b. downward arrow c. heart symbol with a 0 3. WAIT FOR the heart symbol before taking a measurement. 4. Inflate the cuff by quickly squeezing the inflation bulb with the right hand up to 140-150 mmhg. a. If you know that your systolic blood pressure is higher than this, inflate the cuff to a higher value. b. Stop pumping just before you hit the 140 mmhg level in the display window. c. The pressure will tend to go up a little more even after your last pump. 5. Remain still, DO NOT TALK OR MOVE DURING TEST. a. Movement or altered breathing patterns may cause an error message to appear on the display. 6. The cuff will deflate automatically & emit a beep with a flashing heart symbol to signal pulsation of blood through the artery. 7. When measurement is complete, your systolic & diastolic blood pressure will appear alternately with your heart rate/min. 8. TURN OFF POWER!!! 9. If an error message appeared on the display wait ten minutes before taking another reading. 10. Possible reasons for errors - cuff over or under inflated, movement during measurement... Resting Blood Pressure Systolic/Diastolic in mmhg Percentile Fitness Rank (Use Diastolic BP to chose your rank) Men Age 20-29 Men Age 30-39 Fitness Percentile Rank Women Age 20-29 Women Age 30-39 94/60 94/60 99 90/56 90/60 110/70 108/70 90 99/63 100/65 112/72 110/74 80 101/68 104/70 118/78 116/78 70 106/70 110/70 120/80 120/80 60 110/72 110/74 121/80 120/80 50 (average) 112/75 114/76 128/80 124/81 40 118/78 118/80 130/84 130/85 30 120/80 120/80 136/88 132/90 20 122/80 122/82 140/90 140/92 10 130/82 130/90 158/110 168/110 1 141/90 160/110
D. CARDIORESPIRATORY ENDURANCE (AEROBIC FITNESS) Aerobic fitness is really the keystone of any fitness program. It is the ability of the body to use oxygen, an activity that involves cardiovascular, respiratory, blood and cellular enzyme systems. Aerobic metabolism is needed if we are involved in any sustained activity that requires a high expenditure of energy. Endurance types of exercise such as jogging, swimming, and cycling strengthen these organ systems and increase the ability to use oxygen for energy production. To achieve and maintain adequate aerobic fitness, an exercise program requires exercise for 20-30 minutes at least 3X a week at an intensity that elevates the heart rate to 60%-85% of the maximum heart rate. Heart rate is a good index of the severity of the work being performed. Generally speaking, a heart rate of less than 100 beats per minute indicates light work, 100-130 beats/min. moderate work, and greater than 160 beats/min. heavy work. Usually when the heart rate is > 180 beats/min. the subject is near exhaustion, because the efficiency of the heart's pumping action decreases greatly at rates close to the maximum. Maximum heart rate (MHR) declines with age & is most simply estimated as: Maximum heart rate (MHR) = 220 - age. Other scientists have suggested that a more accurate measure is to use this equation called the Miller formula: MHR = 217 - (0.85 X age). Calculate you MHR using both formulas. How much do these values differ? Then estimate your heart rate for work efforts at the 60% & 85% of your maximum using the 1 st MHR. MHR = 220 - Age Miller MHR = 217 - (0.85 * Age) 60% of Maximum Workout MHR * 0.60 85% of Maximum Workout MHR * 0.85 FOREST SERVICE FITNESS TEST Aerobic fitness can be measured using either exercise heart rates or recovery heart rates, because the heart rate of a trained person is lower at a particular sub-maximum workload and returns to resting rate faster after exercise than does the heart rate of an untrained individual. Oxygen debt is the extra oxygen taken in during the recovery period following exercise. This oxygen is used to remove metabolic wastes such as lactic acid and to replenish the energy stores used up during anaerobic metabolism. Thus, the faster, deeper breathing and faster heart rate during recovery are measures of the level of oxygen debt. A trained individual has better blood flow & oxygen delivery during exercise and will suffer lower levels of oxygen debt. Do you know the difference between aerobic and anaerobic metabolism? This test was developed to screen the physical fitness of potential fire fighters for the U.S. Forest Service. It is now widely used as a screening test for many safety and emergency personnel (police, life guards...). It has been found to be a valid and reliable predictor of aerobic fitness. The sub-maximum workload does not place undue stress on the cardiovascular and respiratory systems. The test may be too severe for persons of extremely low fitness and for many persons over sixty years of age. The test requires stepping up and down on a bench 15.75 in (40 cm) high for men and 13 in (33 cm) for women at a rate of 22.5 steps per minute. After 5 minutes the subject sits down and a 15-second recovery pulse count is taken from 15 to 30 seconds after the test. Cautions Do not do this test after strenuous physical activity, after drinking coffee or smoking. Do not do it in a very warm room (> 78 F), or when anxious or excited. Students who have cardiovascular difficulties, such as cardiac insufficiency or hypertension cannot do this test. Experimental Method 1. Rest for 5 minutes before taking the test. 2. Set a timing device for 90 beats/min. 3. Begin exercising to the beat of the timer with an up-up-down-down cadence of your left and right feet. 4. You must step fully up on the bench & stand upright on the step. After 5 minutes of exercise, sit down immediately. 5. Wait 15 seconds & then take your pulse count for exactly 15 seconds. 6. Thus starting exactly at 15 s. & ending exactly at 30 s. after exercise ends. 7. The test is usually more accurate if a lab partner counts your pulse.
Scoring the Forest Service Fitness Test: Use links from the lab notes to print out the needed tables or use the copies provided in lab. The tables allow you to convert that post-exercise heart rate into an estimate of your maximum oxygen consumption per kg body mass per minute. This value is called your VO2 max. & that number represents your maximum aerobic capacity. Step 1: Male & Female Fitness Scores Use your post-exercise, 15 sec heart rate as measured on the previous page. Use the table appropriate for your sex. Find the intersection of your body weight & pulse count in this table to get the first estimate of your maximum O2 use. This score estimates your maximum oxygen delivery system as ml O2/kg/minute. Pulse Count (15 sec) Weight Fitness Score (VO2 max - O2/kg/minute) Step 2: Age-adjusted Fitness (VO2 max) Scores Males & females will use the same table for this step in the calculation. Use the fitness value (O2/kg/min.) from step 1 and your age to find your age-adjusted score in this table. This score estimates your maximum oxygen delivery system as ml O2/kg/minute, adjusted for your age. As you get older, your maximum oxygen carrying capacity is lower because of changes in your lung respiratory volumes heart strength, heart rate & blood pressure. Age-Adjusted Fitness Score (VO2 max) Step 3: Male & Female Fitness Rating Use the table appropriate for your sex. Use the value for VO2 from step 2 & your age to find your overall fitness rating. Fitness Rating
REVIEW QUESTIONS FOR GROUP DISCUSSION Heart Structure 1. Why is the heart built as a double pump (i.e. why right & left sides)? 2. Why do our hearts have atria, if the ventricles supply the force to move blood into the arteries? 3. Label the major blood vessels on the heart diagram for the class. Which vessels carry oxygenated blood? Which deoxygenated? 4. Label the major heart chambers on the heart diagram for the class. Draw 2 lines to show the pathway of blood through the chambers & vessels. 5. Label the valves of the heart on the heart diagram for the class & explain how the valves open & close. 6. Describe your heart sounds & explain what causes those sounds. 7. What is a heart murmur? Describe 2 health problems that can cause heart murmurs. Heart Rate or Pulse 8. Why are lower heart rates given higher fitness estimates in the table? Blood Pressure 9. What does systolic blood pressure measure? 10. What does diastolic blood pressure measure? 11. What does Hypertension mean? What value of BP is used as an indicator of it? 12. Explain 2 of the factors that contribute to atherosclerosis & hypertension in the elderly. 13. Describe 2 types of damage that can be done to your organs or blood vessels by hypertension. Aerobic Fitness 14. What does peripheral resistance mean? 15. Write out the equation showing BP & resistance. 16. How does regular exercise lower your peripheral resistance? 17. What effect does lower peripheral resistance have on your blood pressure? 18. What is the Forest Service Fitness test measuring when it uses your "after exercise" heart rate? 19. How & why does your sex affect your maximum O2 estimation in the Forest Service tables? 20. How & why does your age affect your maximum O2 estimation in the Forest Service tables?