Heart Circulation & Physiology

1. HeartCirculation & Physiology Ch. 18

2. Blood Pathway • Pulmonary circulation – to and from lungs (right side of heart) • Systemic circulation – to and from body (left side) • Renal – to and from kidneys • Hepatic portal – to and from liver • Coronary – to and from heart muscle

3. Heart Valves • Direct blood flow in one direction • AV (atrio-ventricular) valves – supported by chordae tendonae; open when atria contract • Right AV – “tricuspid” valve • Left AV – “bicuspid” or “mitral” valve

5. Semi-lunar valves – open when ventricles contract • Aortic valve – between left ventricle and aorta • Pulmonary valve – between right ventricle and pulmonary trunk

6. Problems when valves “prolapse” or suffer from “stenosis” (scarring); can happen due to genetic defects, strep infections, or heart disease

11. Coronary Circulation • Myocadium too thick for diffusion of blood from heart chambers to be effective • Coronary arteries supply blood to heart muscle.

12. Arteries branch from base of aorta and form a “crown” around the heart • Cardiac veins collect and return blood to circulation

14. Problems happen when blockages occur • Angina pectoris – “chest pain” • Myocardial infarction – “cardiac muscle death”, “coronary”, “heart attack”

18. Heart Physiology • Nodal System – intrinsic system • SA Node – sinus rhythm • AV Node – nodal rhythm (.04 secs)

19. Circuit • Starts with SA node ----AV node ------ AV Bundle (Bundle of His) • Bundle branches (Purkinje fibers)

20. Contraction from apex upwards • Entire process takes .22 secs • Rate controlled by sympathetic and parasympathetic

21. Problems • Arrythmias – irregular rhythm • Fibrillation – ineffective ventricular contraction • Ectopic focus – development of new pacemaker which interferes with normal pacemaker

22. Extrasystole – premature contraction • Heart block – no AV node; requires artificial pacemaker (2 kinds: fixed rate and on-demand)

23. Cardiac Cycle • All events associated with blood flow through heart during one heart beat • Systole – contraction of ventricles • Diastole – relaxation of ventricles • At 75 bpm average cycle is 0.8 secs

24. Heart sounds • “lub” – AV valve closes, louder, longer and more resonant • “dub” – SL valve snaps shut, short, sharp • Left side usually closes before right side, so sounds of individual valves can be distinguished

25. Murmurs – abnormal or unusual sounds; occurs when normally smooth blood flow strikes obstructions or flows in the wrong direction, flow is turbulent and generates sounds.

26. Electrocardiogram (EKG) • Measurement of electrical output of the heart’s electrical system • Consists of 3 types of “deflection waves”: • P wave – impulse from SA node

27. QRS wave – depolarization of ventricles (unequal in size due to size differences of ventricles) • T wave – repolarization of ventricles

29. P-R = beginning of atrial excitation • Q-T = beginning of ventricle contraction

30. Regulation of Rate • Nervous Control • Sympathetic releases norepinephrine to stimulate SA and AV nodes; stress (emotional or physical) • Parasympathetic (via vagus nerves) releases ACh to slow things down

31. Chemical control • Hormones • Epinephrine • Thyroxine

32. atrial natriuretic factor (ANF) - causes vasodilation and kidneys to dump water; lowers blood pressure • Antidiuretic hormone (ADH) – vasoconstriction and tells kidneys to hold water; alcohol interfers with this

33. Physical factors • Age • Gender • Exercise • Body temperature • Fetal rate – 2x adult

34. Pathology • Tachycardia – rapid heart rate • Bradycardia – slow heart rate • Congestive heart failure – ventricles don’t pump effectively, circulation is inadequate • Pulmonary congestion – left side fails • Systemic congestion – right sidefails

35. Hypotension • Hypertension (silent killer); stresses myocardium which enlarges heart, vessels tear which increases platelet deposition and Ca+ deposits

36. Any Questions?