Cardiology A&P

• epicardium: visceral layer of the serous pericardium
• myocardium
• endocardium

visceral layer of the serous pericardium

• -spiral bundles of cardiac muscle cells
• -fibrous skeleton of the heart (criss crossing interlacing layer of connective tissue)
• -anchors muscle fibers
• -limits spread of potentials

continuous with endothelial lining of blood vessels

• r. atrium
• tricuspid valve
• right ventricle
• pulmonary valve (semi lunar)
• pulmonary trunk
• pulmonic artery 
• lungs
• pulm vein
• left atrium
• bicuspid valve
• left ventricle
• aortic semi lunar valve
• aorta
• body
• vena cava(s)

capillary beds of lungs

little nervous systems that allow ions to flow from one cell to another cell

make muscle elastic so cells can pull apart and not rip

• 1. depolarization is due to Na+ influx through voltage gated channels (positive feedback cycle)
• 2. plateau phase due to Ca2+ influx through calcium channels. keeps cell depolarized because a few K+ channels are open
• 3. repolarization due to Ca2+ channels inactivating and K+ channels opening allowing K+ efflux bringing membrane potential back to resting voltage (makes it more negative as it flows out of the cell because of concentration gradient)

• 1. Ca2+ influx triggers opening of ca2+ sensitive channels in the SR
• 2. E-C coupling occurs as CA2+ binds to troponin and sliding of the filaments begins
• 3. duration of the AP and the contractile phase is much greater in cardiac muscle than in skeletal muslce
• 4. repolarization results from inactivation of ca2+ channels and opening of voltage gated K+ channels

-noncontractile cells that initiate and distribute impulses to coordinate depolarization and contraction of the heart (pacemakers)

• 1. pacemaker potential 
• slow depolarization is due to both opening of Na+ channels and closing of K+ channels. (never flat)
• 2. depolarization is when action potential begins when pacemaker potential reaches threshold (depolarization is due to ca2+ influx through ca2+ channels)
• 3. repolarization is due to ca2+ channels inactivating and K+ channels opening. This allows K+ to flow in bringing membrane potential back to its negative voltage

• 1. SA node (pacemaker) 
• fastest depolarizer in myocardium
• 2. AV node
• depolarizes in absence of SA node (50 times a minute)
• delays impulses 0.1 sesconds
• 3. AV bundle of HIS
• only electrical connection between the atria and the ventricles
• 4. Right and left bundle branches
• 2 pathways that carry the impulses toward the apex of the heart through septum
• 5. purkinje fibers
• complete the pathway into the apex and ventricular walls
• depolarize both ventricles 30x/min in absence of AV node

• parasympathetic (vagus) nerve: slows HR
• sympathetic nerves: increase HR

• 1. P wave = depolarization of atria initiated by SA node
• --> impulse delayed at AV node
• 2. QRS complex = ventricular depolarization beginning at apex
• --> flattens when ventricular depolarization is completed
• 3. T wave= ventricular repolarization

• 1. preload
• 2. contractility
• 3. afterload