NURS 8022 Exam 3 Study Guide Latest.

NURS 8022 Exam 3 Study Guide Latest. 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) NURS 8022 Exam 3 Study Guide Latest. Phase 5: Passive ventricular filling (mitral and tricuspid valves open)  Atrial contraction – deoxygenated blood travels from the atria (top) to the ventricles through the AV valves (triscupid & mitral)  Isovolumetric contraction – pressure from the outside of the heart squeezes, closes the valves  Ventricular ejection – cont pressure makes the deoxygenated blood get pumped out form the right side of heart to the pulmonary veins to the lungs to get them oxygenated  Isovolumetric relaxation – release of the blood to the lungs  Atrial filling – oxygenated blood fills the atria  Ventricular filling, AV valves open, allowing oxygenated blood to enter the heart, L side pumps it all to the body Right Heart Function Left Heart Function Pumps blood through the lungs *pulmonary circulation Pumps oxygenated blood through the systemic circulation Delivers blood to the lungs for oxygenation Delivers metabolic waste products to the lungs, kidneys, & liver Is a LOW pressure system Is a HIGH pressure system 3. Understand EKG basics, waves, and intervals Normal electrocardiogram (ECG) -Sum of all cardiac action potentials P wave: Atrial depolarization (atrial contraction) PR interval: Time from the onset of atrial activation to the onset of ventricular activation (0.12-0.20 sec) QRS complex: Sum of all ventricular depolarizations ST interval: Ventricular myocardium depolarized, represents period between depolarization and depolarization of ventricles QT interval: “Electrical systole” of the ventricles - Varies inversely with the heart rate - Approximates time of ventricular contraction HR can be determined with reciprocal of time interval between each heartbeat - R-R interval 4. Remember the basic of the sequence of blood through the pulmonary system, heart, and systemic circulation, (superior vena cava, to RA, through tricuspid valve, into RV, and so on). As well as were there is oxygenated and unoxygenated blood Unoxygenated (venous) blood from systemic circulation to right atrium (RA) via superior & inferior vena cava RA through right AV (tricuspid) valve to right ventricle (RV) RV through pulmonic semilunar valve (pulmonary valve) to pulmonary artery, to lungs for oxygenation Oxygenated blood enters the left atrium (LA) through the 4 pulmonary veins (two from the left lung and two from the right) LA through the left AV valve (mitral valve) into the left ventricle (LV) LV through the aortic semilunar valve (aortic valve) into the aorta, which delivers it to the entire body 5. Function of atria and ventricle Atria act as primer pumps 80 percent of blood flows directly into ventricle from atria before atrial systole Atrial contraction causes additional 20 percent Normally heart can pump 3-4 times as much blood as is needed Therefore if atria fail, not normally symptomatic patient, unless under stress; ex: exercise 6. Understand volumes, EF, Cardiac output, preload, and afterload Cardiac output Is the volume of blood flowing through either the systemic or the pulmonary circuit Is expressed in liters per minute (L/min) Is calculated: CO = HR x SV Normal adult cardiac output at rest is 5 L/min Factors that affect CO: Preload Afterload Frank Starling Law of the heart Laplace’s Law Ejection fraction Is the amount of blood ejected per beat Normal is 55% or higher stroke volume divided by end-diastolic volume Is an indicator of ventricular function Cardiac Index Definition CO indexed against body size Formula- CI = CO/ BSA Normal value = 2.5-4.0 L/min/m2 Decreased CO/CI Increased CO/CI MI HTN Shock Dec vascular resistance Dec HR Pulmonary edema Dec SV Inc metabolic state Negative inotropes Positive inotropes Cardiac tamponade Hypovolemia Valvular heart disease High PEEP Preload: the pressure generated at the end of diastole also called left ventricular end-diastolic pressure (LVEDP) determined by 2 primary factors -Amount of venous return to the ventricle -Blood left in the ventricle after systole or end-systolic volume When preload exceeds physiologic range, further muscle stretching causes a decline in cardiac output Preload is assessed by measuring the filling pressure of each ventricle RV preload = CVP (central venous pressure) (3-8mmHg) LV preload = PAOP (pulmonary artery occlusion pressure) aka PCWP (2- 15mmHg) Clinical significance Represents fluid returning to the heart aka the “filling pressure” Increased preload represents increased myocardial oxygen consumption or (MVO2) Afterload: Is the resistance to ejection during systole Aortic systolic pressure is a good index of afterload for the left ventricle Decreased afterload: Heart contracts more rapidly Increased afterload: Slows contractions and increases work load Afterload is assessed by measuring the resistance in the ventricle during systolic ejection Right ventricle afterload = PVR (100 -250 dynes/sec/cm-5) Left ventricle afterload = SVR (800-1200dynes/sec/cm-5) Clinical significance: Increased afterload = increased work of the heart and increased oxygen demand Factors that increase afterload - Vasoconstriction - Valvular stenosis - Increased blood volume - Factors that decrease afterload: Vasodilation 7. Know different valves and which type they are Purpose of valves -Ensure one way blood flow Atrioventricular valves (AVs) One-way flow of blood from the atria to the ventricles Tricuspid valve: 3 leaflets or cusps Bicuspid (mitral) valve: 2 leaflets or cusps .