NURS 8022 Exam 3 Study Guide: Cardiac

STRUCTURE AND FUNCTION OF THE CV AND LYMPHATIC SYSTEMS 1. Understand the basics of cardiac muscle contraction Cross-bridge cycling -Attachment of actin to myosin at the cross bridge -Myosin head molecule undergoes a position change -Causes thin filaments to slide past thick filaments (contraction) Calcium -Is stored in the tubule system and the sarcoplasmic reticulum -Enters the myocardial cell from the interstitial fluid after electrical excitation, which increases membrane permeability to calcium -Diffuses toward the myofibrils, where it binds with troponin Excitation contraction coupling - Is the process by which an action potential triggers the cycle of events, leading to cross-bridge activity and contraction - Requires calcium - Calcium-troponin complex facilitates the contraction process Myocardial relaxation - Is vital to optimal cardiac function as is contraction - Calcium, troponin, and tropomyosin also facilitate relaxation Troponin release of calcium begins myocardial relaxation. 2. Understand cardiac cycle and what each part represents Cardiac cycle -One contraction and one relaxation -Makes up one heartbeat Diastole (D=R) -Relaxation: Ventricles fill Systole (S=C) -Contraction: Blood leaves the ventricles `Phases of the cardiac cycle Phase 1: Atrial systole or ventricular diastole Phase 2: Isovolumetric ventricular systole Phase 3: Ventricular ejection (semilunar valves open) Phase 4: Isovolumetric ventricular relaxation (aortic valve closes)