1. Heart Continued

2. Review Blood Flow

3. Coronary Circulation
Blood in the heart chambers does not nourish the myocardium (heart muscle)
The heart has its own nourishing circulatory system consisting of
Coronary arteries—branch from the aorta to supply the heart muscle with oxygenated blood
Cardiac veins—drain the myocardium of blood
Coronary sinus—a large vein where all of the cardiac veins come together on the posterior of the heart, receives blood from cardiac veins

4. Coronary Circulation
Blood from the heart enters the coronary arteries through a branch at the base of the aorta.
Blood empties into the right atrium via the coronary sinus

5. Coronary Circulation Angina pectoris:
-Chest pain due to inadequate supply of oxygen to the muscle
-Indication some degree of coronary vessels blockage
Myocardial infarction:
- Medical term for heart attack
-Heart cells die from lack of blood supply
-Usually caused by blockage of one of the coronary arteries

6. The Heart: Conduction System
Intrinsic conduction system (nodal system)
Heart muscle cells contract, without nerve impulses, they use nodes
Heart beat sounds: “lub dub”
Sounds are made by the closing of the valves
Lub is the AV valves closing
Dub is the SA valves closing

7. The Heart: Conduction System
Special tissue:
Sinoatrial node = SA node (“pacemaker”), in right atrium
Atrioventricular node = AV node, at junction of the right atrium near the interatrial septum
Atrioventricular bundle = AV bundle in the interventricular septum
Bundle branches in the interventricular septum
Purkinje fibers spread within the ventricle wall muscles

8. SA node (sino-atrial node)
acts as the heart’s “pacemaker”
cells whose primary function is electrical conduction, not contractility
the action potential produced by its depolarization spreads across the atria
(remember that action potential is the movement of molecules across the membranes of cells to create electrical current)

9. Heart Contractions Impulse spreads to the AV node
Then the atria contract
impulse passes through the AV bundle, bundle branches, and Purkinje fibers
the ventricles contract

10. Heart Contraction

11. Heart Contractions
Figure 11.6

12. The Heart: Cardiac Cycle
The cardiac cycle refers to 1 complete heart beat
Normally .8 sec for 1 cardiac cycle
Cardiac cycle includes:
Systole = contraction
Diastole = relaxation
Relates to the ventricles, unless otherwise stated

13. Heart Contractions Normal Heart Rate: 75 beats/min
Tachycardia—rapid heart rate over 100 beats per minute (tachy= fast)
Bradycardia—slow heart rate less than 60 beats per minutes (brady= slow)

14. Filling Heart Chambers: Cardiac Cycle

15. The Heart: Cardiac Cycle
Cardiac cycle—events of one complete heart beat
Mid-to-late diastole—blood flows from atria into ventricles
Ventricular systole—blood pressure builds before ventricle contracts, pushing out blood
Early diastole—atria finish refilling, ventricular pressure is low