1. Heart Circulation & 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 arteries supply blood to heart muscle.
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 side fails

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

36. Any Questions?