1. Cardiovascular System

2. Consists of blood, heart and blood vessels Cardiology – study of the heart

3. The Heart Located in the mediastinum – mass of tissue that extends from the sternum to the vertebral column Rests on the diaphragm Approx. the size of closed fist

4. Apex – pointed end (leans toward left) Base – rounded end (toward right) Mass: females ~ 250g males ~ 300g

5. Function of the Heart Pump oxygenated blood to the tissues and deoxygenated blood to the lungs

6. Coverings of Heart Pericardium – double layered sac that covers the heart o Parietal pericardium – outer layer o Visceral pericardium – inner layer (also called epicardium) o Pericardial cavity – fluid filled space between the two layers; contains fluid to decrease friction

7. Layers of the Heart Wall Epicardium – thin, protective outer layer Myocardium - thick middle layer; makes up most of heart; function is to pump blood Endocardium - smooth, inner lining; also forms valves of heart

8. Chambers of the Heart 4 chambers o 2 atria – (upper, thin-walled) receive blood Have auricles – pouches that increase the surface area of the atria so it can hold a greater volume of blood Separated by interatrial septum o 2 ventricles – (lower, thicker) pump blood Separated by interventricular septum

9. Right atrium -receives deoxygenated blood from superior vena cava, inferior vena cava & coronary sinus o Superior vena cava – returns blood to heart from head, neck & arms o Inferior vena cava – returns blood to heart from chest, abdomen, pelvis & legs o Coronary sinus – returns blood to right atrium from myocardium

10. Left atrium - receives oxygenated blood from the lungs via the pulmonary veins

11. Right ventricle - receives blood from the right atrium & pumps it out to the lungs via the pulmonary arteries Left ventricle - forms apex o Receives blood from left atrium & pumps it out to tissues of the body via the aorta

12. Features of Ventricles Trabeculae carneae – ridges in the ventricle Papillary muscle - masses of myocardium that project into the ventricles

13. Heart Valves Function is to keep blood flowing in one direction (prevents backflow) 2 types of valves o 1. Atrioventricular valves (AV) o 2. Semilunar valves (SL)

14. Atrioventricular Valves Tricuspid valve – between right atria & right ventricle (3 cusps) Bicuspid valve – between left atria & left ventricle (2 cusps) o Also called the mitral valve Chordae tendineae - connective tissue strands that connect papillary muscle to cusps of atrioventricular valves

15. Semilunar Valves valves at the base of large vessels that carry blood from the ventricles Pulmonary semilunar valve –at exit of right ventricle in base of pulmonary trunk Aortic semilunar valve – at exit of left ventricle in base of ascending aorta

16. Valves open & close in response to pressure: Atria fill with blood…causes increased pressure on AV valves. Atria contract, AV valves open, blood flows into ventricles. Ventricles fill with blood…causes increased pressure on SL valves. Ventricles contract, SL valves open, blood flows into vessels.

17. Coronary Circulation: Blood Supply for the Heart Coronary arteries - surround the heart like a crown o Branch off the ascending aorta o Supplies heart cells with oxygen & nutrients Coronary sinus – returns blood to the right atrium

18. Fetal Circulation Blood doesn’t need to go to lungs in a fetus 2 shunts: o Foramen ovale – an opening on the interatrial septum of fetal heart Closes to form the fossa ovalis o Ductus arteriosum – shunts blood from the pulmonary trunk to the aortic arch Closes to form the ligamentum arteriosus (connects arch of aorta and pulmonary trunk) o Both shunts close by birth or w/in 1 st year o If shunts don’t close, surgery is required

19. Conduction System Cardiac muscle is autorhythmic – it generates its own action potentials for muscle contraction Both atria contract simultaneously, followed by both ventricles Specialized cardiac muscles act as nerve tissue to distribute the impulse

20. 1. Excitation begins in sinoatrial node (SA node…also known as the pacemaker) in the right atrium. 2. Action potential spreads to left atrium, allowing both atria to contract simultaneously 3. Action potential spreads to atrioventricular node (AV node) located between right & left atria o Action potential slows at AV node so atria can fully empty and ventricles can fill; also AV node has smaller fibers

21. 4. Action potential spreads to Atrioventricular bundle, then to right & left bundle branches within the interventricular septum 5. Purkinje fibers send the action potential to the ventricles, causing them to contract 0.2 seconds after atria contract

22. Electrocardiogram (EKG or ECG) Recording of electrical activity of heart to check the conduction system Uses multiple electrodes attached to body Stress test – EKG during strenuous exercise; compares resting heart to stressed heart

24. P wave – atrial contraction (depolarization); SA node activity PQ interval – impulse delay at AV node QRS complex – ventricular contraction (depolarization);Purkinje fiber activity o It’s so much larger due to greater muscle mass of ventricles T wave – ventricular relaxation (repolarization) **why can’t we see atrial relaxation??**

25. EKG Abnormalities Large P Wave - enlarged atria Large Q wave – myocardial infarction (heart attack) Large R wave - enlarged ventricles Flat T wave - coronary artery disease Wider PQ interval - abnormal conduction Arrhythmia – abnormal beating of heart due to malfunction of conduction system o Tachycardia - fast heart rate o Bradycardia - slow heart rate o Asystole - lack of heart rate

26. Cardiac Cycle All the events associate with one complete heart beat Systole – contraction Diastole – relaxation Atrial systole = ventricular diastole atria contract, ventricles relax AV valves open, SL valves closed ventricles fill with blood Atrial diastole = ventricular systole atria relax, ventricles contract AV valves close, SL valves open atria fill with blood

27. Heart Sounds Caused by the turbulence of blood when heart valves close Stethoscope – instrument used to listen to heart sounds Lubb – first sound heard; AV valves closing after ventricular systole begins Dupp – second sound heard; SL valves close at beginning of ventricular diastole

28. Heart Murmur Abnormal heart sound Gurgling noise before, between or after lubb-dupp sound Most murmurs indicate a valve disorder Mitral stenosis – narrowing of the mitral valve Mitral valve prolapse – part of mitral valve is pushed back into the atria o Occurs in 10-15% of population ( 65% are female)

29. Heart Disorders 1. Ischemia – partial block of blood flow due to constriction or obstruction of a vessel 2. Hypoxia – lack of O 2 to heart muscle 3. Angina – chest pain 4. Myocardial infarction – heart attack due to myocardial cells dying 5. Sudden cardiac death – conduction system stops; heart stops beating 6. Congenital defects – present at birth

30. Nervous System Control Autonomic nervous system – no conscious control o Heart controlled by two branches of ANS 1. Sympathetic Nervous System – increases heart rate & force of contractions due to release of norepinephrine 2. Parasympathetic Nervous System – decreases heart rate due to the release of acetylcholine Both work together to maintain homeostasis