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FUNCTIONS OF THE ventricles to complete ventricular HEART filling. 1. Generating blood pressure 2. Routing blood RIGHT ATRIUM 3. Ensuring one-way blood flow Superior vena cava and the...

FUNCTIONS OF THE ventricles to complete ventricular HEART filling. 1. Generating blood pressure 2. Routing blood RIGHT ATRIUM 3. Ensuring one-way blood flow Superior vena cava and the inferior vena cava 4. Regulating blood supply Smaller coronary sinus SIZE, FORM, & LOCATION BASE - Larger, flat part at the opposite LEFT ATRIUM end of the heart Four pulmonary veins APEX - Blunt, rounded point of the heart RIGHT AND LEFT VENTRICLES ANATOMY OF THE HEART Major pumping chambers. PERICARDIUM a. FIBROUS PERICARDIUM RIGHT VENTRICLES b. SEROUS PERICARDIUM Pumps blood to pulmonary truck SEROUS PERICARDIUM LEFT VENTRICLES a. Parietal pericardium Pumps blood to the AORTA b. Visceral pericardium (epicardium) HEART VALVES HEART CHAMBERS Atrioventricular (AV) valves INTERNAL ANATOMY - Allow blood to flow from the atria into RIGHT AND LEFT ATRIA the ventricles Heart receive blood - Prevent it from flowing back into the from veins. atria Tricuspid and Bicuspid (mitral) Primarily as reservoir Valve Forces blood into the Semilunar (SV) valves CARDIAC VEINS – drain blood from - allow blood to flow from the ventricles the cardiac muscle into the arteries Drain blood into the coronary sinus - preventing blood from flowing into the right atrium backward from the arteries into the COLLATERAL ROUTES - ensure ventricles blood delivery to heart even if major vessels are occluded Aortic and Pulmonary Semilunar Valve HISTOLOGY: HEART WALL CORONARY CIRCULATION Composed of three layers of - is the functional blood supply to the tissue: heart muscle itself 1. Epicardium (visceral pericardium) 2 PARTS: Thin, serous membrane. forming ARTERIAL SUPPLY the smooth outer surface of the heart. Blood Supply to the Heart It consists of simple squamous CORONARY ARTERIES – supply blood epithelium overlying loose connective to the wall of the heart Originating from tissue and adipose tissue base of aorta 2. Myocardium Thick, middle layer of the heart LEFT CORONARY ARTERY - HAS 3 MAJOR PARTS: Composed of cardiac muscle cells and 1. Anterior interventricular artery is responsible for contraction of the heart 2. Circumflex artery chambers. 3. Left marginal artery 3. Endocardium RIGHT CORONARY ARTERY – Smooth inner surface of the heart chambers is the HAS 2 PARTS: Consists of simple squamous epithelium 1. Posterior interventricular artery over a layer of connective tissue. 2. Right marginal artery Allows blood to move easily through the heart. VENOUS SUPPLY Heart valves are formed by folds of Blood from the Heart endocardium tha include a thick layer of connective tissue Unlike skeletal muscle that requires neural stimulation to contract, cardiac muscle can contract without neural HISTOLOGYCARDIAC stimulations. MUSLCE All the cells of the conduction system can produce spontaneous action ❑Striations are less regularly arranged potentials. and less numerous than in skeletal muscle The conduction system of the heart includes the sinoatrial node, ❑Rich in mitochondria - produces ATP atrioventricular node, ❑Extensive capillary network provide atrioventricular bundle, right and adequate O2 to cardiac muscle left bundle branches, and Purkinje fibers. COORDINATION OF CARDIAC MUSCLE STIMULATION AND SINOATRIAL (SA) NODE CONTRACTION : - Heart’s pacemaker 1.The heart is at rest, chambers are - Located in the superior wall of the relaxed. right atrium and Initiates the 2.Cardiac muscle cells in the atrial wall are contraction of the heart. stimulated as action potentials spread Action potentials originate in the SA across the atrial wall and towards the node and spread over the right and left ventricles. atria, causing them to contract. 3.Cardiac muscles in the atrial wall Larger number of Ca 2+ channels - contract, pushing blood into the ventricles. produces action potentials at a faster 4.Cardiac muscle cells in the ventricular rate than other areas of the heart wall are stimulated as action potentials spread ATRIOVENTRICULAR (AV) NODE across the ventricular wall from the apex of the heart towards its base. - Located in the lower portion of the right atrium. 5.Cardiac muscle cells in the ventricular wall contract, pushing blood into the great - Delays the electric impulse to allow ventricular filling of 0.8 milliseconds arteries. When action potentials reach the AV CONDUCTION SYSTEM OF node, they spread slowly through it HEART and then into a bundle of specialized cardiac muscle called the Contraction of the atria and ventricles atrioventricular (AV) bundle is coordinated by specialized cardiac muscle cells in the heart wall that form the conduction system of the heart. PURKENJE FIBERS ELECTROCARDIOGRAM (EKG) - Passes through the apex of the heart ECG (EKG) and extend through the ventricles record of electrical events in heart - It can function as a backup diagnoses cardiac abnormalities pacemaker if all other pacemakers fail uses electrodes Ectopic beats - when the action potential is generated from other parts of the conducting system aside from the SA node COMPONENTS OF ECG/EKG P wave: ACTION POTENTIAL PATH depolarization of atria THROUGH HEART The P wave represents atrial muscle 1. SA node depolarization. It is normally small, smoothly rounded, and no wider than 2. AV node (atrioventricular) 0.12 second 3. AV bundle QRS complex: 4. Right and Left Bundle branches depolarization of ventricles 5. Purkinje fibers contains Q, R, S waves Normal QRS width is 0.04 to 0.10 second. "The pumping action of the heart is accomplished by the rhythmic Atrial repolarization happens relaxation and contraction” simultaneously. BLOOD PRESSURE - blood exerts a T wave: force on the muscular walls on the repolarization of ventricles blood vessels T waves are not normal more than 5 120/80 mmHg mm SYSTOLE - refers to the events in the heart during, contraction of the two top chambers (atria) and two lower chambers (ventricles) 90-120 mmHg DIASTOLE - is characterized by relaxation of the lower chambers which allows the ventricles to fill in preparation for contraction 60-80 mmHg CARDIAC CYCLE CARDIAC OUTPUT (CO) - it refers to the repetitive pumping - volume of blood pumped by either process begins with the onset of ventricle of the heart each minute cardiac muscle contraction and ends STROKE VOLUME (SV) with the beginning of the next - is the volume of blood pumped per contraction ventricle each time the heart contracts HEART RATE (HR) ❑ ATRIAL SYSTOLE - number of times the heart contracts - contraction of the two atria. each minute ❑VENTRICULAR SYSTOLE CO= SV x HR - contraction of the two ventricles. Cardiac output = Stroke ❑ ATRIAL DIASTOLE volume x Heart rate - refers to relaxation of the two atria ❑ VENTRICULAR DIASTOLE INTRINSIC MECHANISM - refers to relaxation of the two ventricles. Mechanisms contained within the heart itself. HEART SOUNDS Force of contraction produced by cardiac muscle is related to the degree Heart sounds are produced due to of stretch of cardiac muscle fibers the closure of heart valves. PRELOAD - amount of blood that first heart sound makes a ‘lubb’ returns to the heart specifically the second heart sound makes a ‘dupp’ ventricles The first heart sound is due to the AFTERLOAD - pressure against which closure of the atrioventricular valves. the ventricles must pump blood The second heart sound is due to the STROKE VOLUME - volume of blood closure of the semilunar valves. ejected by the left ventricle during each systole PRELOAD - degree of myocardial REGULATION OF stretch at the end of diastole & just before contraction HEART FUNCTION STARLING'S LAW - the more the heart is filled during diastole, the more forcefully it contracts the higher the preload, the higher the stroke volume CONTRACTILITY changes in blood pressure cause changes in frequency of action - force generated by the contracting enhanced by myocardium potentials - catecholamines, sympathetic activity involves the medulla oblongata and with medications such as the 3 D’s Digoxin, Dopamine, Dobutamine CHEMORECEPTOR REFLEX - the higher the contractility, the higher - a chemicals can affect heart rate and the stroke volume. stroke volume. AFTERLOAD Chemical actions: - pressure or resistance that the - epinephrine and norepinephrine from ventricles must overcome to eject blood through the semi-lunar valves the adrenal medulla can increase heart rate and stroke volume excitement, - directly proportional to the BP & anxiety, and anger can increase diameter of blood vessels cardiac output - the higher the afterload, the lower the depression can decrease cardiac stroke volume output medulla oblongata has chemoreceptors for changes in pH and CO2 EXTRINSIC MECHANISM K+, Ca2+, and Na + affect cardiac Mechanisms external to the heart function Nervous or chemical regulation (a) Parasympathetic - decrease heart rate (b) Sympathetic - increase heart rate NERVOUS REGULATION: BARORECEPTOR REFLEX - is a mechanism of the nervous system that plays an important role in regulating heart function. monitor blood pressure in the aorta and carotid arteries