BIOLOGY 20 Lecture Notes - Lecture 23: East Los Angeles College, Pericardium, Cardiac Arrhythmia
Document Summary
The force of contraction is directly related to degree of stretch of cardiac muscle cells prior to contraction (preload) Ventricles tend to eject as much blood as they receive within constraints of muscle tissue. Slow heartbeat and exercise increase venous return to the heart increasing sv. Blood loss and extremely rapid heartbeat decrease sv. As edv increases, stroke volume increase sv edv. Contractility refers to how hard the myocardium contracts for a given preload. Hypercalcemia can cause strong, prolonged contractions and even cardiac arrest in systole. Digitalis raises intracellular calcium levels and contraction strength. Hypocalcemia can cause weak, irregular heartbeat and cardiac arrest in diastole. Hyperkalemia reduces strength of myocardial action potentials and the release of. The degree of ventricular stretching during ventricular diastole. Affects ability to muscle cells to produce tension. The resistance against which the heart has to pump.
