CVS 200L MBBS.pptx

CARDIOVASCULAR SYSTEM PHYSIOLOGY 200 LEVEL (MBBS) 1  OVERVIEW Cross sectional Electrocardiogr areas of am (ECG)...

CARDIOVASCULAR SYSTEM PHYSIOLOGY 200 LEVEL (MBBS) 1  OVERVIEW Cross sectional Electrocardiogr areas of am (ECG) different parts of Cardiac output: the Functional Control of Vascular Anatomy of stroke volume system, the Heart and cardiac Arteries and the output and cardiac The vascular Arterioles The muscle system; Basic overall The origin of principles of design of Heart pressure, flow CV system cardiac and resistance cycle 2  The Overall Design of the cardiovascular system Cardiovasc ular System Vasculature Heart (Blood vessels) The heart – central pump The vasculature–distributing & collecting tubules Function- collection and distribution of blood 3  THE FUNCTIONAL ANATOMY OF THE HEART A muscular organ that pumps blood throughout the circulatory system. The Heart pumps blood into the blood vessels. Blood vessels circulate the blood throughout the body. Blood transports nutrients and oxygen to the tissues and removes carbon dioxide and waste products from the tissues Dimensions (averagely): 12cm X 9cm (LxB) like the size of a closed fist ≈ 250g weight 4 Location: -Between the 2 lungs in the mediastinum. Rest on the diaphragm, near the midline (⅔to the left). 5  THE WALL OF THE HEART Organization Pericardium Myocardium Endocardium Peri/external/ Myo/muscle Endo/Inner surface Cardium (heart) Pericardium is the outer covering of the heart. It is made up of two layers: A. Outer parietal pericardium B. Inner visceral pericardium. The space between the two layers is called pericardial cavity or pericardial space and it 6 7  The wall of the heart Cont’d…… OUTER PARIETAL PERICARDIUM  It forms a strong protective sac for the heart. It helps also to anchor the heart within the mediastinum. Outer fibrou s Layer Outer parietal pericardiu Inner m Serou s Layer 8  The wall of the heart Cont’d…… Outer Fibrous layer formed by thick fibrous connective tissue. Fibrous: consisting of or characterized by fibers. It is a typical connective tissue predominantly consisting of inelastic fibers Connective tissue: tissue found in between other tissues in the body. Basic components of all connective tissues are; Fibers (elastic and collagenous fibers), Ground substance and cells 9  The wall of the heart Cont’d…… It is attached to the diaphragm below and it is continuous with tunica adventitia (outer wall) of the blood vessels, entering and leaving the heart. Its fibrous nature makes it protect the heart from over stretching 10  The wall of the heart Cont’d…… Inner Serous layer It consists of mesothelium, and a small amount of connective tissue. Mesothelium contains squamous epithelial cells which secrete a small amount of fluid, which lines the pericardial space. The fluid prevents friction and allows free movement of heart within pericardium, when it contracts and relaxes. 11  The wall of the heart Cont’d…… INNER VISCERAL PERICARDIUM It lines the surface of myocardium and it is made up of flattened epithelial cells. This layer is also known as epicardium. Function of the Pericardium (Summary) 1. Protects and anchors the heart 2. Prevents overfilling of the heart with blood 3. Allows for the heart to work in a relatively friction-free environment 12 CHAMBERS OF THE HEART AND COMMUNICATIONS 13 Chambers of the heart and communications..cont’d LEFT SIDE OF THE HEART RIGHT SIDE OF THE HEART Left atrium (LA) and left 1. Right atrium (RA), Right ventricle (LV). ventricle (RV), Sino atrial node (pacemaker), 1.LA has a thin wall and is Atrioventricular node a low pressure chamber 2. Receives deoxygenated 2.It receives oxygenated (Venous) blood from blood from the lungs Superior vena cava (Head through Pulmonary veins. neck and Upper limbs) and Inferior vena cava (Lower 3. Blood from left atrium part of the body) enters the left ventricle through 3. RA communicates with mitral valve (bicuspid RV through Tricuspid valve valve). From the right ventricle 4. LV pumps the arterial 4. Pulmonary artery carries blood to venous blood from right different parts of the body 14 ventricle to lungs to be Atrioventricular and semi lunar Valves of the Heart Left Atrioventricular valve is otherwise known as MITRAL valve or BICUSPID valve. It is formed by two valvular cusps or flaps Right Atrioventricular valve is known as TRICUSPID valve and it is formed by three cusps. Brim of AV is attached to AV ring (Fibrous connection between atria and ventricles) Cusps of the valves are attached to papillary muscles through chordae tendineae 15 Semilunar Valves: (Semi (half) Lunar (moon) shaped valves the openings of systemic aorta (AORTIC Valve) pulmonary artery (PULMONARY Valve) Semilunar valves are made up of three flaps. Semilular valves open only towards the aorta and pulmonary artery and prevent the backflow of blood into the ventricles 16 Blood Dynamics SUMMARY Right atrium  tricuspid valve Right ventricle  pulmonary semilunar valve  pulmonary arteries  lungs Lungs  pulmonary veins  left atrium Left atrium  bicuspid valve  left ventricle  aortic semilunar valve  aorta Aorta  systemic circulation 17  Septa of the Heart Right and left atria are separated from one another by a fibrous septum called INTERATRIAL SEPTUM. Right and left ventricles are separated from one another by INTERVENTRICULAR SEPTUM. The upper part of this septum is a membranous structure, whereas the lower part of it is muscular in nature The Atria are separated from the ventricles by a band of thick fibrous connective tissue called Annulus Fibrosus 18  The Cardiac Muscle (MYOCARDIUM) The myocardium is located as the middle layer of the wall of the heart. it is formed by cardiac muscle fibers also called MYOCYTES Myocardium forms the bulk of the heart and it is responsible for pumping action of the heart. Contrary to the skeletal muscles, this Different muscle is involuntary in nature types of muscle (myocardium) fibers 1. Those 2. Those 3. Those which form which form which form contractile the conductive unit pacemaker system 19 20 1. (Fibers Contractile Unit of Heart)  they are striated similar to skeletal muscles fibers structurally.  it is bound by sarcolemma with a nucleus placed centrally  has myofibrils embedded in the sarcoplasm  Actin, myosin, troponin and tropomyosin are all contractile proteins present in the sarcomere  similar sarcotubular system to that of the skeletal muscle NOTE: Cardiac muscle fiber is branched while the skeletal muscle is not branched  It also contains INTERCALATED DISKS: it is a double tough membranous structure found b/w branches of neighboring fibers. Formed from fusion of membrane of myocardial fibers  the Disks form adherens junction. 21 The cardiac muscle is like a physiological Syncytium; it is without continuity of the cytoplasm. The fibers are also separated from each other SYNCYTIUM: Syncytium means tissue with cytoplasmic continuity between adjacent cells  Gap junction is: formed from fusion between membranes of adjacent fibers  It is permeable to ions and precipitates rapid conduction of action potential between fibers.  NOTE: Because of the aforementioned property, cardiac muscle fibers act like a single unit. This is 22 Syncytium is present both in atria and ventricles. Both areas of syncytium are connected by a thick non-conducting fibrous ring called the ATRIOVENTRICULAR RING 23 Atrioventricular Ring 24 2. Muscle Fibers which Form the Pacemaker  these fibers are specialized or modified to form the pacemaker  Pacemaker is a structure positioned in the heart that generates the impulses for heart beat. It is formed by pacemaker cells called P cells.  The Pacemaker in the human heart is formed by Sinoatrial node 3. Muscle Fibers which Form Conductive System  Conductive system of the heart is formed by modified cardiac muscle fibers.  Impulses from SA node are transmitted to the atria directly. However, the impulses are transmitted to ventricles through various components of conducting system 25 THE PROPERTIES OF CARDIAC MUSCLE (Overview) Excitability Rhythmicity Conductivity Contractility 26  The Conduction System It refers to the system involved with the origin and spread of cardiac excitation „PACEMAKER Pacemaker is the structure of heart from which the impulses for heartbeat are produced. It is formed by the pacemaker cells called P cells. In mammalian heart, the pacemaker is sinoatrial node (SA node). Lewis Sir Thomas in 1918 named SA node the pacemaker of the heart 27  The Conduction System Location: 1. Superior lateral wall of RA 2. Below the opening of superior vena Cava  Its fibers do not contain contractile elements.  Its fibers are continuous with fibers of atrial muscle which causes rapid distribution of impulses  Rhythmicity of the SA node is about 70 to 80/minutes. Relatively more than others SA node : 70 to 80/minute, AV node : 40 to 60/minutes, Atrial muscle : 40 to 60/minute, 28 Purkinje fibers : 35 to 40/minute Ventricular muscle  The Conduction System The SAN is a ∼2-mm-wide group of small elongated muscle cells that extends for ∼2 cm down the sulcus terminalis. It has a rich capillary supply and sympathetic and parasympathetic (right vagal) nerve endings. The SAN generates an AP about once a second (sinus rhythm) 29  Experimental Evidences for SA node 1. Stimulation of SA node Heart rate 2. Destruction of SA node = immediate stoppage of the heartbeat. Atrioventricular node resumes after a while (slowly) 3. Local cooling and warming of SA node= the heart rate respectively. 4. Sinus venosus (Amphibian)/warm and cold water Ringer solution 5. Stannius Ligature: First stanius ligature (B/w sinus venosus and right auricle) Auricloventricular rhythm Second: B/w auricles and ventricles (Idioventricular rhythm). 30  Ionic basis of electrical activity  Unstable resting membrane potential (SA node)  Slow depolarization (Sodium leakage into SA fibers)  Slow depolarization (Calcium ions influx)  Rapid depolarization (More calcium influx) (- 40mV) 31 32  Components of Conductive System 1. SA node 2. AV node 3. Bundle of His 4. Right and left bundle branches 5. Purkinje fibers The impulse spreads from the SAN across the atria at ∼1 m/s. Conduction to the atrioventricular node (AVN) is facilitated by larger cells in the three internodal tracts. 33  Components of Conductive System The internodal tracts Bachmann Wenckebac Thorel (anterior) h (middle) (posterior) 34 The Conduction System 35 36  THE CARDIAC CYCLE The cardiac cycle is the sequence of mechanical and electro-chemically coordinated events that occurs during a heart beat When the heart beats at a normal rate of 72/minute, duration of each cardiac cycle is about 0.8 second Atrial events are divided into two divisions: 1. Atrial systole = 0.11 (0.1) sec 2. Atrial diastole = 0.69 (0.7) sec Ventricular events are divided into two divisions: 1. Ventricular systole = 0.27 (0.3) sec 2. Ventricular diastole = 0.53 (0.5) sec 37  THE CARDIAC CYCLE Events of the cardiac cycle: ATRIAL EVENTS 1. Atrial systole 2. Atrial Diastole VENTRICULAR EVENTS 3. Isometric Contraction 4. Rapid Ejection Phase 5. Slow Ejection Phase 6. Prodiastole 7. Isometric Relaxation 8. Rapid Filling 9. Slow Filling 10.Last Rapid Filling 38  EVENTS OF ATRIAL SYSTOLE 1.Atrial systole completes Ventricular filling (< 20%) of ventricular volume (Except with increased heart rate) then the proportion increases. Why? 2.Also called Last rapid filling phase or presystole. (0.11) secs. 3.Atrial systole is not essential for the maintenance of circulation. Eg A person with atrial fibrillation. 4.Pressure: Intra­atrial pressure, intra- ventricular pressure, Ventricular volume 39  ATRIAL DIASTOLE Atrial diastole starts simultaneously with Ventricular systole (about 0.69 secs) Simultaneously, ventricular systole also starts. Why the long duration for Atrial diastole? Out of 0.7 sec of atrial diastole, first 0.3 sec (0.27 sec accurately) coincides with ventricular systole. Ventricular diastole starts and it lasts for about 0.5 sec (0.53 sec accurately) Ending part of atrial diastole coincides with ventricular diastole for about 0.4 sec. So, the heart relaxes as a whole for 0.4 sec. 40 41  Isometric contraction ISO= the same Metric= Based on meter as a unit of measurement Increased tension without change in length of muscle fibers. Also called Isovolumetric contraction (Ventricle contracts as a closed chamber Sharp increase in ventricular pressure Heart sound: 1st (Closure of the Atrioventricular valves at the beginning of the phase) Significance: The pressure build-up here is responsible for opening of the semi-lunar valves NOTES: the A/V valves open into the ventricles while the Semi lunar valves open into the Aorta and pulmonary Vein respectively. What is the significance 42  Isometric contraction Ventricular depolarization is associated with the QRS complex of the ECG. Isovolumetric contraction of the ventricles = AV valves to bulge into the atria= rise in atrial pressure (c wave) then a fall (x descent) 43  Rapid Ejection The outflow valves open when pressure in the ventricle exceeds that in its respective artery. Note that pulmonary artery pressure (∼15 mmHg) is considerably less than that in the aorta (∼80 mmHg). Flow into the arteries is initially very rapid (rapid ejection phase)  Contraction is directly proportional to Ejection. Explain Duration of this period is 0.22 second44  Ejection Phase Closure of the Semilunar valves is caused by backflow of blood = a small increase in aortic pressure, the Dicrotic notch. Closure of the semilunar valves is associated with the Second heart sound (S2) The ventricle ejects ∼70 mL of blood (Stroke Volume), so if EDV is 120 mL (120-70= 50). 50 mL is left in the ventricle at the end of systole (end-systolic volume). Ejection Fraction = EDV/Stroke volume 45  Fraction End diastolic volume: is the amount of blood remaining in each ventricle at the end of diastole. It is about 130 to 150 mL per ventricle 46  Significance of determining ejection fraction Ejection fraction is the measure of left ventricular function. Index for assessing ventricular contractility Conditions that can decrease Ejection fraction Myocardial infarction and Cardiomyopathy 47  Protodiastole Protodiastole is the first stage of ventricular diastole, Duration of this period is 0.04 second. As pressure in aorta and pulmonary artery increases and pressure in ventricles drops. When intraventricular pressure becomes less than the pressure in aorta and pulmonary artery, the semilunar valves close. No other change occurs in the heart during this period. Closure of semilunar valves during this phase produces 48  ISOMETRIC RELAXATION PERIOD All the valves of the heart are closed. Both ventricles relax as a closed chamber No change in both volume and length of muscle fibers Decreased intraventricular pressure Duration isometric relaxation period is 0.08 seconds Opening of the Atrioventricular valves for 49  RAPID FILLING PHASE Opening of the Atrioventricular valves Flow of accumulated blood from the atria into the ventricles RAPIDLY About 70% of filling takes place during this phase, which lasts for 0.11 second NOTE: During the rapid filling phase, blood returning to the Atria pass through unhindered into the ventricles 3rd Heart sound (Rushing of blood into the 50  SLOW FILLING PHASE/LAST RAPID FILLING PHASE After the RAPID rush of blood, the ventricular filling becomes slow. Also called Diastasis About 20% of filling occurs in this phase. Duration = 0.19 second Last rapid filling phase (ATRIAL KICK) About 10% filling of the ventricles due to Atrial systole 51