1. Heart Conduction & Cardiac Cycle

2. Cardiac Circulation Myocardium nourished by coronary artery
Coronary veins drain into coronary sinus (enlarged vessel on backside of heart)
Coronary sinus empties into right atrium

3. Heart Conduction
Cardiac muscle does not have to be controlled by nervous system
Muscle cells in different areas of heart have different rhythms

4. Heart Rate influences
Autonomic nervous system increases & decreases heart rate
Intrinsic conduction system (nodal system) causes heart muscle depolarization (electric impulse that causes heart beat)

5. Heart Beat SA node (also known as pacemaker)
Located in right atrium
Starts heart beat
Impulse travels through atrium to the AV node
Atrium contract

6. Impulse through AV bundle through bundle branches to Purkinje fibers in apex
Ventricle contracts starting at apex and moving toward the atria.
Blood forced upward out of the aorta

7. Cardiac Cycle = complete heart beat
Atria contract simultaneously
Atria relax
Ventricles contract
Systole = contraction of ventricle
Diastole = relaxation of ventricle

8. Mid to late diastole Ventricle completely relaxed
Pressure low in heart
Blood flowing passively into and through atria into ventricles
Semilunar valves closed, AV valves open
Then atria contract, forcing blood into ventricles

9. 2. Ventricular systole
Ventricles contract (atria relax-filling with blood)
Pressure increases, closing AV valves (lub sound)
Higher pressure in ventricles, than in arteries so forces semilunar valves open and blood is forced into arteries

10. 3. Early diastole Ventricles relax
Semilunar valves close (preventing back flow)
Dup sound
Intraventicular pressure drops, until low enough for AV valves to be forced open