I. Function of Circulation<\/p>\n
A. Transport\/distribute essential substances<\/p>\n
B. Remove wastes<\/p>\n
C. Closed Circulation-includes pump, distributing and collecting tubes, exchange tubes (capillaries), ICF (cytoplasm) and ECF (interstitial fluid)<\/em><\/p>\n D. Open Circulation –includes pump, distributing tubes (arteries), collecting tubes (veins), ICF, ECF<\/em><\/p>\n II. Heart as a pump<\/p>\n A. Muscular pump with chambers and valves.\u00a0Number of chambers vary, with birds and mammals having 2 atria and 2 ventricles; left ventricle has thickest muscular wall due to having the hardest job<\/em><\/p>\n B. Cardiac Muscle<\/p>\n 1. Features –Striated with sarcomeres, small cells, one nucleus, extensive SR, T tubules, cells connected electrically at intercalated disks which have gap junctions<\/em><\/p>\n 2. Gap junctions allow electrical current to flow from one cell to another resulting in a functional syncitium (a single coordinated unit)<\/p>\n 3. Rhythmic systolic and diastolic contractions & relaxations are the result of action potentials<\/p>\n a. Pacemaker cells\u00a0<\/strong>in\u00a0sinoatrial node<\/strong> initiate action potentials.\u00a0 All cells are capable of spontaneous action potentials but the Sinoatrial node does it sthe fastest and thus sets the pace.<\/em><\/p>\n -unstable resting membrane potential that drifts upward gradually depolarizing due to slow influx of sodium (this is called the\u00a0pacemaker potential<\/strong>) without corresponding outflow of potassium<\/p>\n -membrane shows spontaneous depolarization until threshold is reached and this causes fast calcium – sodium channels to open and mainly\u00a0calcium and some sodium flow inward from the ECF causing depolarization to threshold, leading to an action potential<\/p>\n -for repolarization, potassium channels open and potassium leaves the cell and then potassium channels close and cycle can start again – every .8 seconds for 75 bpm. However, as repolarization begins, the calcium channels are very slow to close and thus a plateau appears before rapid repolarization.<\/p>\n b. Conduction pathway\u00a0<\/strong>through heart: SA node to both atria, to AV node (slight delay to finish atrial contraction) AV bundle to Purkinje fibers of ventricular walls<\/p>\n <\/p>\n 4. Electrocardiogram\u00a0<\/strong>(EKG or ECG) records electrical activity of heart<\/p>\n a. P wave – atrial depolarization<\/p>\n b. QRS complex – ventricular depolarization<\/p>\n c. T wave – ventricular repolarization<\/p>\n 5. No tetany in cardiac muscle due to lengthy absolute refractory period.<\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" I. Function of Circulation A. Transport\/distribute essential substances B. Remove wastes C. Closed Circulation-includes pump, distributing and collecting tubes, exchange tubes (capillaries), ICF (cytoplasm) and ECF (interstitial fluid) D. Open Circulation –includes pump, distributing tubes (arteries), collecting tubes (veins), ICF, … Continue reading