Heart Lecture 2 PDF

The Cardiovascular System Dr Nicola King  Learning Outcomes Describe the gross anatomy of the heart Describe the different components of the cardiac cycle Describe blood flow through the heart Describe the major types of blood vessel Why Do We Need A Cardiovascular...

The Cardiovascular System Dr Nicola King  Learning Outcomes Describe the gross anatomy of the heart Describe the different components of the cardiac cycle Describe blood flow through the heart Describe the major types of blood vessel Why Do We Need A Cardiovascular System? © Deliver nutrients and oxygen to the tissues © Remove waste products © Repair injuries © Defend against attackers © We are too large to manage all this via diffusion A closed circuit containing pumps, tubes and valves Head, arms brain Coronary vessels Right heart lungs Left heart Hepatic artery liver Spleen, Portal vein GI tract kidneys Trunk, legs Gross Anatomy The Cardiac Layers Key 8) Fibrous pericardium 9) Parietal pericardium 10) Pericardial cavity 11) Epicardium 12) Myocardium 13) Endocardium The chambers The valves Blood Supply Circulation Through the Heart Key 1) Superior vena cava 2) Pulmonary artery 3) Pulmonary veins 4) Right atrium 5) Tricuspid valve 6) Inferior vena cava 7) Aortic arch 8) Pulmonary artery 9) Pulmonary veins 10) Left atrium 11) Bicuspid valves 12) Left ventricle 13) Right ventricle The Cardiac Conduction System Key 1) Sinoatrial (S-A) node 2) Interatrial septum 3) Atrioventricular (A-V) node 4) Atrioventricular bundle (bundle of His) 5) Right crus 6) Left crus 7) Interventricular septum 8) Purkinje’s fibres  In order to carry out its pumping role the heart must perform a repeating series of closely coordinated actions. Together these actions make up the cardiac cycle.  The Cardiac Cycle The cardiac cycle represents all of the events associated with blood flow through the heart during one complete heart beat. This includes: © one complete PQRST on the ECG; © Atrial systole and diastole followed by ventricular systole and diastole; © 2 heart sounds © One opening and closing of the atrioventricular and semilunar valves The ECG  The heart sounds 1. 1st heart sound caused by closure of the tricuspid and mitral valves 2. 2nd sound is caused by closure of the aortic and pulmonary valves (sometimes splits, sounding “lubb- terrupp”). Two more sounds can be detected by phonocardiography: 3. 3rd sound caused by the rush of blood into the relaxing ventricles during early diastole. 4. 4th sound occurs just before the first sound and is caused by atrial systole.  Mechanical Events of the Cardiac Cycle 1. Ventricular filling (duration 0.5s; inlet valves [tricuspid and mitral] open, outlet valves [pulmonary and aortic] closed 2. Isovolumetric contraction (duration 0.05s, all valves closed) 3. Ejection (duration 0.3s; inlet valves closed, outlet valves open) 4. Isovolumetric relaxation (duration 0.08s, all valves closed) The cardiovascular system = a closed circuit containing pumps, tubes and valves Let’s now think about the tubes  The Main Tubes Based on direction Veins Arteries ©Venae cavae ©Aorta or trunk ©Arteries ©Sinuses ©Arterioles ©Veins ©Venules Organ/ tissue Capillaries Blood Vessel Structure Exchange Occurs in the Capillaries Regulation of the CVS Blood Pressure = CO x PVR © Cardiac Output © Peripheral vascular resistance Cardiac output = HR x SV © Heart rate © Stroke volume  Control of Heart Rate Autonomic System Control of the firing rate of the sinoatrial node Sympathetic speeds up Parasympathetic slows down  Control of Stroke Volume Contractility of the ventricular cardiomyocytes Sympathetic increases force and speed of contraction Parasympathetic – no effect Degree of stretch of the cardiac fibres – Starling’s law of the heart  Starling’s Law of the Heart End-diastolic volume (EDV) (volume in ventricle at end of relaxation) Residual Stroke volume EDV contraction SV Larger Stronger Larger EDV contraction SV  Control of Total Peripheral Resistance This is all about whether the arterioles are constricted or dilated Lots of constriction = lots of resistance Lots of dilation = low resistance Lots of different mediators involved Let’s Take a Break Mentimeter quiz for part 2