Understanding the Cardiovascular System: Blood, Heart, Adaptation & Disorders

1. Overview of the Cardiovascular System Topics to be addressed: Blood Anatomy of Blood Vessels Anatomy of the Heart The Conduction System The Cardiac Cycle Cardiodynamics Blood Flow and its Regulation Adaptation and Disorders of the Cardiovascular System

2. Cardiovascular Adaptation • Blood, heart, and cardiovascular system work together as unit Allows for both short- and long-term responses to physical and physiological changes (eg. exercise or blood loss)

3. Cardiovascular Adaptation : Standing Up • In rising from a lying to a standing position, the effect of gravity is to cause blood to accumulate in capacitance veins of the legs and feet. • Less blood returns to heart (decreased EDV) • Stroke Volume decreases (SV is a function of EDV) • Cardiac Output decreases (CO = SV X HR) • Blood Pressure decreases • Decreased blood flow to brain What prevents us from fainting?

4. Cardiovascular Adaptation : Standing Up • A rapid response by the cardiovascular system raises blood pressure and restores blood flow to brain within a few beats. • 1. Carotid and aortic baroreceptors detect low BP • 2. Cardiovascular center in medulla of brainstem activates sympathetic branch of ANS, decreases parasympathetic • 3. Sympathetic nerves to blood vessels cause vasoconstriction in arteries and veins (increasing EDV) • 4. Sympathetic nerves to heart increase heart rate and force of ventricular contraction, increasing stroke volume and restoring cardiac output and blood pressure

5. Cardiovascular Adaptation : Response to Exercise • Light exercise • Driven by metabolite buildup, extensive vasodilation occurs, increasing circulation to active muscles • Skeletal muscle activity enhances venous return via “muscular pump” • Venous return increases and increases stretch on ventricular wall (Frank–Starling principle); increased stretch increases contractility to increase stroke volume and cardiac output • Heavy exercise Induces same changes as light exercise, but also activates sympathetic nervous system • Sympathetic stimulation increases heart rate and contractility, increasing cardiac output to about four times resting level • Selective vasoconstriction restricts blood flow to “nonessential” organs (e.g., digestive system) and redirects blood flow to skeletal muscles, lungs, and heart. Blood supply to brain is unaffected

6. Cardiovascular Adaptation: Changes in Blood Distribution during Exercise

7. Exercise, Cardiovascular Fitness, and Health

8. Hemorrhage

9. The Cardiovascular Response to Hemorrhaging • Entire cardiovascular system adjusts to maintain blood pressure • and restore blood volume • Short-Term Elevation of Blood Pressure (seconds) • Carotid and aortic reflexes stimulate cardiovascular center in medulla • Increase cardiac output by increasing heart rate & contractility • Peripheral vasoconstriction improves venous return (increasing preload, SV, CO) Hormonal effects (minutes) • Increase cardiac output by increasing heart rate and contractility • Increase peripheral vasoconstriction (E, NE, ADH, angiotensin II) • Long-Term Restoration of Blood Volume (hours to weeks) Recall of fluids from interstitial spaces Aldosterone and ADH promote fluid retention and reabsorption Thirst increases to replace fluid volume Erythropoietin stimulates red blood cell production to replace RBC loss

10. Circulatory Shock • Short-term responses compensate for blood losses of up to 20% of total blood volume • Failure to restore blood pressure results in circulatory shock Intense vasoconstriction shunts blood away from organs and into bloodstream to maintain blood pressure Prolonged vasoconstriction causes cells in organs to die and organ damage results

11. Disorders of the Cardiovascular SystemHypertension : high blood pressure • Risk Factors: • genetics • gender (males more at risk) • high cholesterol levels • obesity • chronic stress • cigarette smoking • often no known cause • Strain on the system: • increased work for heart, leading to heart enlargement • greater oxygen demands lead to ischemia • stress on blood vessel walls promotes arteriosclerosis • Clinical Intervention: • lifestyle, diet and exercise changes • drugs: calcium channel blockers, beta blockers, diuretics, ACE inhibitors

12. Disorders of the Cardiovascular SystemAtherosclerosis Atherosclerosis is an Inflammatory Disease

13. The link between cholesterol and cardiovascular disease Cholesterol is a necessary component of cell membranes and a building block for steroid hormones. However, high levels of blood cholesterol are associated with an increased risk of cardiovascular disease. LDL (low density lipoprotein) is one form of cholesterol in the blood. It is thought to carry cholesterol toward tissues and high levels are associated with atherosclerosis, which is why it is considered the “bad cholesterol” HDL (high density lipoprotein) is another form of cholesterol in the blood. It is thought to carry cholesterol away from tissues to the liver, and is considered the “good cholesterol”

14. Disorders of the Cardiovascular System : The model for atherosclerosis Step 1: High levels of LDL in blood lead to accumulation of LDL in tunica intima LDL Step 2: Chemical reaction of LDL in intima leads to lymphocyte and monocyte attraction from blood; LDL recognized as foreign WBC

15. Plaque Disorders of the Cardiovascular System : The model for atherosclerosis Step 3: Chemicals released from lymphocytes and macrophages induce inflammation, causing thickening in wall of artery • Plaques contain: • Lipids • Connective tissue • Calcium deposits • “hardening of arteries”

16. Disorders of the Cardiovascular System : Atherosclerosis Result: Narrowing of opening : Decreased blood flow to tissues Decreased blood flow : Heart works harder to overcome resistance Calcification over time : Loss of ability to dilate/constrict

17. Disorders of the Cardiovascular System :Coronary Artery Disease When atherosclerosis affects coronary arteries, the function of the heart is compromised

18. Disorders of the Cardiovascular System :Coronary Artery Disease Decreased coronary blood flow can lead to angina pain and eventually to a heart attack Symptoms of Heart Attack: Chest discomfort. Most heart attacks involve discomfort in the center of the chest that lasts more than a few minutes, or that goes away and comes back. It can feel like uncomfortable pressure, squeezing, fullness or pain.    Discomfort in other areas of the upper body. Symptoms can include pain or discomfort in one or both arms, the back, neck, jaw or stomach.    Shortness of breath with or without chest discomfort.   Other signs may include breaking out in a cold sweat, nausea or lightheadedness        As with men, women's most common heart attack symptom is chest pain or discomfort. But women are somewhat more likely than men to experience some of the other common symptoms, particularly shortness of breath, nausea/vomiting, and back or jaw pain.

19. A stress test is often used to assess heart problems Patient is asked to walk on a treadmill while heart is being monitored A medical team is present to watch for changes in ECG, shortness of breath, chest pain, or other signs of heart problems

20. Disorders of the Cardiovascular System :Coronary Artery Disease Coronary bypass surgery is one technique to restore blood flow to the heart wall

21. Disorders of the Cardiovascular System :Coronary Artery Disease Less invasive options include balloon angiography and/or the insertion of a stent to open the blocked artery

22. Disorders of the Cardiovascular System: Arrhythmias • Atrial fibrillation: • Atria can depolarize at rate of 500 beats per minute without driving ventricle beyond normal limits • Atrial wall “quivers” • Blood clots may form near the atrial walls, creating emboli and leading to stroke • Ventricular fibrillation: • Purkinje cells fire abnormally; muscle overly sensitive to stimulation • Ventricle wall “quivers” and fails to pump blood out of heart • Leads to cardiac arrest

23. Disorders of the Cardiovascular System: Congestive Heart Failure • Heart cannot pump enough blood to body organs Causes: • damage to heart: infection, heart attack, congenital defects • coronary artery disease • heart valve disease or defects leads to backward flow in system • As heart pumps inadequately, blood backs up on venous side • Edema in tissues, including visible swelling in limbs • Back up into lungs interferes with breathing

24. Aging and the Cardiovascular System • Changes in Blood • Decreased hematocrit impacts oxygen delivery • Changes to clotting factors increase clot likelihood • Pooling of blood in legs due to venous valve deterioration • Changes in Blood Vessels • Arteries become less elastic leading to wall rupture or aneurysm • Plaque deposits and calcification of vessel walls reduce blood flow and may trigger clot formation leading to stroke • Changes within the Heart impact Cardiac Output • Changes in nodal and conducting cells • Reduced elasticity of cardiac (fibrous) skeleton • Progressive atherosclerosis and valve stiffening • Replacement of damaged cardiac muscle cells by scar tissue