Chapter 25 - Cardiac Structure and Function PDF

CHAPTER 25: STRUCTURE AND FUNCTION OF THE CARDIOVASCULAR AND LYMPHATIC SYSTEMS Tutoring Week 6 CIRCUL ATORY SYSTEM KNOW THE PATHWAY OF BLOOD IN THE BODY!!!! Deoxygenated Blood (start) - Superior Vena Cava – R...

CHAPTER 25: STRUCTURE AND FUNCTION OF THE CARDIOVASCULAR AND LYMPHATIC SYSTEMS Tutoring Week 6 CIRCUL ATORY SYSTEM KNOW THE PATHWAY OF BLOOD IN THE BODY!!!! Deoxygenated Blood (start) - Superior Vena Cava – Right Atrium – through Tricuspid Valve – Right Ventricle – through Pulmonary Valve – through Pulmonary Artery – to the lungs (to be oxygenated) Oxygenated Blood – Pulmonary Vein – Left Atrium – through Mitral Valve – Left Ventricle - through Aortic Valve – Aorta – to the body (end) ***Take the time to know this!!  C I RC U L AT ORY SYSTEM https://www.youtube.com/watch? v=_vZ0lefPg_0 WALL OF THE HEART The heart is located diagonally in the mediastinum, the area above the diaphragm and between the lungs. Pericardium – outer membranous sac surrounding the heart; physical barrier to protect against infection and inflammation; this sac holds pericardial fluid 3 layers of the heart wall: Epicardium- Outer layer; closest to pericardium Myocardium- Middle layer of muscle Endocardium- Inner layer; continuous with the endothelium that lines all blood vessels, creating a closed system of blood circulation Epi ="above" (above other layers) Myo = muscle Endo = internal (innermost layer)  CORONARY VESSELS Circulatory vessels of the heart- supply the heart with oxygen Must remain oxygenated or ischemia will occur Blockages in these vessels cause myocardial infarctions (MI) Heart supplies blood to itself before anything else! The L coronary artery supplies blood to the LA and LV The R coronary artery supplies blood to the RA, RV, SA node, and AV nodes  THE CARDIAC CYCLE One cardiac cycle is completed with each ventricular contraction and the relaxation period that follows it  beginning of one ventricular contraction to the beginning of the next ventricular contraction 5 Phases: 1. Atrial systole- BOTH atria contract and push blood through the tricuspid and mitral valves into the ventricles; the semilunar valves (pulmonic and aortic) are closed during this phase 2. Beginning of ventricular systole- BOTH ventricles contract which causes increased pressure in the tricuspid and mitral valves causing them to close- this is heart sound S1 or the “lub” of “lub-dub” 3. Period of rising pressure- the semilunar valves open as pressure in the ventricles exceeds that in the arteries 4. Beginning of ventricular diastole- pressure in the ventricles drops below the arterial pressure and the semilunar valves snap shut- this is heart sound S2 or the “dub” 5. Period of falling pressure- blood flows from the  CARDIAC CONDUCTION SYSTEM The myocardium of the heart has its own conduction system. Pacemaker cells are concentrated at two sites: high in the right atrium at the sinoatrial node (SA node) and at just above the tricuspid valve in the atrial wall at the atrioventricular node (AV node). SA node: supplied by both SNS and PNS nerve fibers- resting rate of 60-100 beats/min (causes bilateral atrial contraction) Pacemaker of the heart**** AV node: supplied by PNS fibers from the Vagus nerve- rate of 40-60 beats/min due to PNS innervation Bundle of His/Purkinje fibers: travel down and  E L E C TR O C A RD I O G RA M (ECG OR EKG) EKG is an electrical Depolarization = meter of conduction contraction through the heart Repolarization = relaxation P wave= atrial depolarization (contraction) QRS complex= ventricular depolarization, atrial repolarization T wave= ventricular Repolarization (Return to Resting) QT interval= beginning of ventricular contraction  E L E C TR O C A RD I O G RA M (ECG OR EKG) EKG paper Voltage is read on the vertical axis Time is read on the horizontal axis Cardiac cells move by way of the sliding filament theory, almost identical to skeletal muscle movement, however cardiac muscle: has more mitochondria because of the high ATP demands of cardiac muscle only one nucleus C A R D I AC has intercalated discs that help to facilitate C ON D U C T ION SYSTEM- quick movement of action potentials between M YOC A R D IA L C E L L S cells Has more T tubules that supply ions to help facilitate quick transmission of action potentials  C A R D I AC C ON D U C T ION SYSTEM- M YOC A R D IA L C E L L S  CARDIAC CONDUCTION SYSTEM- M YO C A R D I A L C E L L S 1. Troponin covers active sites on tropomyosin when they are not in use. During an action potential, calcium binds to the troponin and in turn the tropomyosin is moved, exposing the active sites. 2. Myosin heads, which have ADP and P molecules attached to them, then form a cross-bridge with actin by binding to the active sites. 3. The ADP and P molecules are then released from the myosin head, in this process the myosin head moves the actin filament toward the center of the sarcomere in a move called a power stroke. 4. A molecule of ATP then attaches to the head of the myosin, causing the myosin to let go of the active site. 5. This ATP molecule then hydrolyzes (breaks apart) which cocks the myosin head, leaving ADP and P molecules are on the head, ready to repeat the process. https://www.youtube.com/watch?v=dpxalWACO7k  Why do cardiac muscle cells have more QUESTIONS mitochondria than skeletal muscle cells?  Why do cardiac muscle cells have more mitochondria than skeletal muscle cells? QUESTIONS To provide for the increased energy demands of the heart and to have ATP readily available at all times  What is the purpose of intercalated discs QUESTIONS in cardiac muscle?  What is the purpose of intercalated discs in cardiac muscle? QUESTIONS Allow impulses to travel quickly between cardiac tissue  C AR D IAC P E R F OR M A N C E : C AR D IAC OU T P U T Stroke volume (SV): the amount of blood pumped by the heart with each beat Cardiac output= SV x HR Contractility: the strength of the cardiac cells to contract/shorten Laplace law: from physics- the tension on the walls of a hollow sphere or cylinder is dependent on the pressure of the contents and the radius More pressure = more tension on the walls Frank-Starling law of the heart: End diastolic volume: the amount of blood in the ventricles just before contraction (systole) at the end of the filling phase (diastole) Volume after “filling” has occurred Literally the blood volume after diastole  PRELOAD VS. AFTERLOAD Preload: the physiological stretching of Afterload: the pressure the ventricles the ventricles after diastole must push against to squeeze blood (relaxation/filling phase) through the semilunar valves to go to This primes the heart to pump blood out the lungs or to the body to the body High vascular resistance = High Relaxation or “filling phase” afterload Ventricles filling with blood coming Example: The heavier something is, the down from the atria more energy/force we must expel to In order to increase preload, stroke move it volume, and cardiac output, we need o The ventricles must work harder to… give IV fluids to increase blood against a higher pressure/more return to the heart/giving vasopressors to cause vasoconstriction (blood vessels resistance constrict to increase blood return to the heart) A narrower aortic valve (aortic stenosis) In order to decrease preload, stroke will result in an increased afterload volume, and cardiac output, we need (more pressure required to get that to… give diuretics to remove extra fluid valve open) from the blood volume and decrease how much the ventricles are going to stretch  BLOOD VESSEL STRUCTURE Know the order of blood flow through the blood vessels: From heart  arteries  arterioles  capillaries  venules  veins  to heart  Poiseuille Las: a small Pressure: mmHG; change in the radius force exerted on a of a vessel= a large liquid per unit area change in flow Resistance: FACTORS opposition to blood Compliance: ability to expand; veins have flow; increased AFFECTING resistance= more compliance than arteries decreased flow BLOOD FLOW Laminar vs. turbulent flow: when blood runs into an obstacle (a Velocity: speed split in vessels, plaque) it becomes less linear and the velocity is reduced  Systolic BP (top number)= highest arterial pressure after ventricular contraction (systole); Diastolic BP (bottom number)= lowest arterial pressure during ventricular filling (diastole) Preload Contractility Vessel diameter Sympathetic nervous activity Blood viscosity REGUL ATION OF Humoral regulation- vasodilation and BLOOD PRESSURE vasoconstriction Baroreceptors - in the aorta & carotid sinus sense changes in the amount of blood in circulation and send signals to the cardiovascular center in the brainstem Chemoreceptors - in the aorta and carotid sinus sense changes in the chemical makeup of the blood and are sensitive to oxygen, carbon dioxide, and pH levels; an increase in PaCO2 concentration or arterial pH causes a rise in HR, stroke volume, and BP to try and rid the body of extra CO2 (body is compensating)  Coronary perfusion pressure: the difference in pressure between the aorta and coronary vessels Autoregulation: ensures constant coronary REGUL ATION OF artery blood flow; constant map of 60-140 CORONARY o Ensures there is blood flow despite changes in CIRCUL ATION BP Autonomic regulation: PNS and SNS control  Picks up extra fluids/materials and brings LYMPHATIC them into the bloodstream so blood can SYSTEM send it to the kidneys  VIDEOS LevelUpRN: https://www.youtube.com/watch?v=C1FuEGkXlYE Crash Course: https://www.youtube.com/watch?v=X9ZZ6tcxArI Armando: https://www.youtube.com/watch?v=hpQFToprlH8 Simple Nursing: https://www.youtube.com/watch?v =-q4jJVoVqPU