Heart Final Notes PDF

HEART! Location: Ventral body cavity à Thoracic cavity à Mediastinum cavity à Pericardial cavity o Tilted to the left Linings o Pericardium o Fibrous – outer layer § Composed of collagen bundles that make it TOUGH; anchor the heart to diaphragm and great vessels o Serous – thin inner serous membrane...

HEART! Location: Ventral body cavity à Thoracic cavity à Mediastinum cavity à Pericardial cavity o Tilted to the left Linings o Pericardium o Fibrous – outer layer § Composed of collagen bundles that make it TOUGH; anchor the heart to diaphragm and great vessels o Serous – thin inner serous membrane; produces serous fluid: § Parietal Pericardium Fussed to inner surface of fibrous pericardium; encases heart-like sac; at great vessels, it folds under itself and forms another layer that adheres directly to heart § Visceral Pericardium innermost layer; also, as epicardium; considered most superficial layer of heart wall o Pericardial cavity – between parietal and visceral pericardia; contains -very thin layer of Serous fluid (pericardial fluid); fluid acts as lubricant, decreasing friction as heart moves o Visceral pericardium rests in top of thin layer of areolar connective tissue; contains large fat deposits 3 Layers of the Heart 1. Epicardium – visceral pericardium (outermost layer) 2. Myocardium (middle layer) 3. Endocardium – super smooth 4. layer (inner most layer) Heart Anatomy Blood Flow 1. Deoxygenated Blood Enters the Right Atrium: Deoxygenated blood from the body returns to the heart via the superior and inferior vena cava and enters the right atrium. 2. Right Atrium Contracts: The right atrium contracts, pushing blood through the tricuspid valve into the right ventricle. 3. Right Ventricle Contracts: The right ventricle contracts, pumping deoxygenated blood through the pulmonary valve into the pulmonary artery. 4. Blood Travels to the Lungs: The pulmonary artery carries deoxygenated blood to the lungs, where it picks up oxygen and releases carbon dioxide through the process of gas exchange. 5. Oxygenated Blood Returns to the Heart: Oxygenated blood from the lungs returns to the heart via the pulmonary veins and enters the left atrium. 6. Left Atrium Contracts: The left atrium contracts, pushing blood through the mitral valve into the left ventricle. 7. Left Ventricle Contracts: The left ventricle contracts, pumping oxygenated blood through the aortic valve into the aorta. 8. Blood Distributed to the Body: The aorta carries oxygenated blood to the rest of the body, delivering oxygen and nutrients to tissues and organs. 9. Deoxygenated Blood Returns to the Heart: Deoxygenated blood returns to the heart via the superior and inferior vena cava, and the process repeats. Coronary Circulation: o Coronary arteries o Leave heart to take O2 to heart muscle (feed the heart muscle) – have a left and right Coronary artery o When people get blockage, it creates a dam and if the heart doesn’t receive O2 it becomes hypoxic (w/o O2) § Muscle pain in the heart is called angina o Myocardial Interaction (MCI) (meaning death of muscle in the heart) § Piece of the heart muscle dies Minor/mild MCI – very small Big MCI – about the size of a quarter § Can create a new path but takes a long time (for blood to travel) § BUT heart muscle can not replace itself o Cardiomegaly à Heart enlargement Cardiac Muscle Tissue Anatomy and Tissue Cardiac Muscle Cells o Heart does not require conscious intervention to elicit cardiac muscle to contract ; cardiac muscle exhibits autorhythmic; sets its own rhythm w/o need for input form nervous system o Autorhythmic § Can generate an action potential, and contractile cell = to contract Electrophysiology of Cardia Muscle Tissue o Sinoatrial node (SA node) – in upper right atrium, slightly inferior and lateral to the opening of the superior vena cava o Under Normal conditions: SA node has fastest intrinsic rate of depolarization – about 60 or more times per min. o Rate is subject to influence form SNS and PNS o SA node misfiring § If the SA node is misfiring, they can receive a pacemaker to regulate the pace o Atrioventricular node (AV node) – Posterior and medial to tricuspid valve; slower than SA node 40 beats per min o If the SA node fails, the AV node can pick of the slack but instead of doing 60 beats per min its now 40 beats per min. If the AV node fails, the Bundle branch can pick do it, but it drops to 20 beats per min. ECG/EKG o Electrocardiogram (ECG) – important clinical tool for examining health of heart; graphic depiction of electrical activity occurring in all cardiac muscle cell over a period EKG Waves o P wave – atrial depolarization (the atrial are getting the signal) o QRS complex – Ventricular depolarization o T wave – depolarization repolarization (getting set back up again) Dysrhythmias o Atrial fibrillation – generally not life threating because atrial contraction isn’t necessary for ventricular filling; manifest on EKG tracing as “irregularly irregular” o Ventricular fibrillation – immediately life-threating and manifest in EKG with chaotic activity o Treated with defibrillation (electric shock to heart); depolarizes all ventricular muscle cells simultaneously and throws cells into their refectory periods o Ideally, SA node will resume pacing heart after shock is delivered The Cardiac Cycle Overview o Each cardiac cycle consists of one period of relaxation (diastole) and one period of contractions (systole) for each chamber of the heart. o Atria systole (atria’s contract) while Ventricular diastole (ventricles relaxes) o Ventricular systole (ventricles contract) while Atria diastole (Atria’s relaxes) o It’s the mechanical events of the heart in 1 heartbeat o Atrial and ventricular diastoles and systoles occur at diff. times because of Av node delay; both sides of heart are working to pump blood into their respective circuits simultaneously Parts 1. 2. 3. 4. of the Cardiac Cycle Ventricular Filling Isovolumetric Contraction Ventricular Ejection Isovolumetric Relaxation Ventricular Filling o Period during which blood drains from Atria into ventricles o Mitral and Tricuspid valves but be open o Aortic/Pulmonary Semilunar valve must be closed o 2 Parts o 1) Passive Filling § Due to force of gravity, flows 70% of blood into the ventricles Force of gravity = Right Atrium (Top Floor) goes to the Right Ventricle (Bottom Floor) o 2) Atrial Contraction § Squishing reaming blood from the Right Atrium in the Right Ventricle Isovolumetric Contraction o Isovolumetric = Equal volume (volume doesn’t change), Contraction (Contract) o Ventricles are filled with blood § ALL valves are shut (Mitral, Tricuspid, Aortic/Pulmonary Semilunar valves) o The Walls of the ventricles begin to contract § No blood is leaving, just contracting (to build up pressure to be able to open the Semilunar valves) Ventricular Ejection o Ejection = leaving o pressure in ventricles rises to level higher than in pulmonary trunk and aorta; pushes semilunar valves open; rapid outflow blood from ventricles occurs o The cuspids valves remain closed o Approx. 70ml of blood pumps from each ventricle; about 50ml of blood remains in each ventricle (end-systolic volume (ESV)) o end-systolic volume = how much o Summary: o Ventricles contract à increases the pressure on the blood, once’s pressure exceeds that of the pulmonary trunk and aorta the semilunar valves eject blood into vessels Isovolumetric Relaxation o Isovolumetric = Equal volume (volume doesn’t change), Relaxation (Relax = Not Contracting) o Final Phase is brief; occurs as ventricular diastole begins and pressure declines in ventricles o Semilunar valves snap shut o Blood is neither being ejected from nor entering ventricles; volume briefly remains constant o Cuspids Valves must be closed; Semilunar Valves must be closed Cardiac Output Cardiac Output: amount of blood pumped by each ventricle per minute o Formula – CO = SV × HR o CO = Cardiac Output ( 1 min.) o SV = Stroke Volume (1 beat) way to remember : Stroke and Beat your meat! o HR = Heart Rate (1 min.) Stroke Volume: the amount of volume of blood pumped out of the ventricle in 1 beat o In average heart, resting stroke volume is equal to about 70ml : o 120ml (EDV) – 50ml (ESV) = 70ml (SV) o Example: C0 = 70ml (SV) × 70ml (HR) à at rest CO = 4900 ml/min o 4900 ml is almost 5 liters (average human has 4-6 liters of blood in the body) Factors that Influence Heart Rate o Sympathetic Nervous System o Tells HR to increase as well as CO o Parasympathetic Nervous System o Tells HR to slow down as well as CO Factors that Influence Stroke Volume (stroke volume = how much blood can we get out in one contraction/beat) o Preload o Contractility o Afterload Preload: the amount of blood in the heart prior to contraction o Influenced by Venous Return (mostly by skeletal contraction) o 1) Skeletal Muscle Contraction o 2) Breathing § Pressure changes in the thoracic cavity push blood to the heart o 3) Veins have valves, to prevent backflow Contractility: the force the muscle is using o Increasing contractility will increase stroke volume o Decreasing contractility will do opposite – it will decrease the stroke volume o Factors that influence: o Starlings Law- that more the muscle fibers are stretch the more forcefully § The more the cardiac muscles are stretched the more forcefully they will contract o Sympathetic Stimulation § Increase HR and SV will make the heart more contractile o Amount of Ca: is going cause increase contraction (Skeletal muscle contraction) § Increases SV and CO Afterload o Refers to force that right and left ventricles must overcome to eject blood into their respective arteries o Largely determined by blood pressure in arteries of both pulmonary and systemic circuits o As afterload increases, ventricular pressure must be greater to exceed pressure in atrial pulmonary and systemic vessels and open semilunar valves o Usually associates with those that have high blood pressure (hypertensive) o Back flow that comes from pulmonary trunk and aorta