Cardiovascular System PDF

Cardiovascular System PJ1311 Phil Roberts Structure of Lectures Cardiovascular system structure – heart and blood vessels function - electrophysiology and cardiac cycle, gas exchange Components – RBC/WBC Clotting process Control blood pressure ne...

Cardiovascular System PJ1311 Phil Roberts Structure of Lectures Cardiovascular system structure – heart and blood vessels function - electrophysiology and cardiac cycle, gas exchange Components – RBC/WBC Clotting process Control blood pressure nervous control hormonal control/ cytokines Pathophysiology and treatment Coronary artery disease Hypertension Arrhythmias Overview of the Cardiovascular system Main components of the cardiovascular system: Blood vessels Blood Heart Overview of the Cardiovascular system Main components of the cardiovascular: Blood vessels Blood Heart The cardiovascular system is: A series of tubes: The blood vessels Filled with fluid: Blood Closed system Connected to a pump: Heart Pulmonary and systemic circulatory systems Overview of the Cardiovascular system Pressure generated in the heart propels blood through the system continuously The blood picks up oxygen (lungs), nutrients (GI) and deliver these to the body cells. Simultaneously remove cellular wastes for excretion (liver/renal system) Overview of the Cardiovascular system Primary function of the CV system is the transport of materials to and from all parts of the body. Blood vessels (conduction system) Blood (carrier) Heart (pump) Flow Blood flows in one direction only How? Valves in the heart and veins ensures that the blood moves in one direction Blood Flow: Pressure Changes Flows down a pressure gradient Highest at the heart (driving P), decreases over distance Hydrostatic pressure in vessels Decreases 90% from aorta to vena cava Blood Flow: Pressure Changes Pressure falls continuously as blood moves from the heart. Why? Because of friction (fluids & vessels) That friction creates a resistance (that opposes the movement). The Heart Structure of the Heart The heart is composed mostly of myocardium STRUCTURE OF THE HEART Aorta Pulmonary Superior artery vena cava Auricle of Right left atrium Pericardium atrium Coronary artery and vein Right ventricle Left ventricle Diaphragm The heart is encased within The ventricles occupy the bulk of a membranous fluid-filled the heart. The arteries and veins all sac, the pericardium. attach to the base of the heart. The Heart and Major Blood Vessels  Aorta Pulmonary semilunar valve Structure of the Heart The heart valves ensure one-way flow Right pulmonary Left pulmonary arteries arteries Superior Left pulmonary vena cava veins Right atrium Left atrium Cusp of the AV (bicuspid) valve Cusp of a right AV Chordae tendineae (tricuspid) valve Papillary muscles Left ventricle Right ventricle Inferior vena cava Descending aorta One-way flow through the heart is ensured by two sets of valves.  Heart Valves Ventricular contraction = Systole  Heart Valves Ventricular Relaxation = Diastole Layers of the Heart Coronary Arteries Cardiac Cells Myocardial cells Bulk of the heart Contractile cells – mechanical force Pacemaker cells (autorhythmic cells) 1% Spontaneous action potentials – coordinate contraction No contribution to mechanical force Action potentials (pacemakers) – excitation myocardium – contraction (Excitation-Contraction coupling) 18 ctrical Conduction in the Heart https://open.oregonstate.education/app/uploads/sites/  Excitation-Contraction Coupling (ECC) 1. Impulse arrives at the muscle cell membrane- in the form of electric current (Action Potential) 2. Plasma membrane is depolarized subsequently leading to cellular depolarization. 3. Depolarization spreads to T-tubules in muscle (cardiac, skeletal) generating a contraction (Ca2+ wave) 21 Excitation-Contraction coupling 22 Action Potentials 1) Myocardial cells 2) Pacemaker cells 1. Myocardial cell Action Potential Myocardial cell Action Potential Phase 4: Resting membrane potential. Phase 0: Depolarization. Voltage-gated Na+ channels opens generating an inward Na+ current. Phase 1: Initial repolarization. Na+ channels close. K+ channels opens. Outward K+ current. Myocardial cell Action Potential Phase 2: Plateau. Two events: 1) decrease in K+ permeability (smaller outward current) 2) Ca+ inward current Phase 3: Repolarization. Ca+ channels close and K+ channels opens (again). Outward K+ current.  1. Myocardial cell Action Potential Phase 2: Plateau. Two events: 1) decrease in K+ permeability (smaller outward current, less K+ moving out) 2) increase of Ca+2 permeability (Ca+2 moving in) Specific in cardiac tissue Provides additional length (msec) for the Action Potential (AP) when compared to neuronal/skeletal AP) Long refractory period in cardiac muscle  2. Pacemaker Action Potential Phase 4: Unstable resting potential Due to If, (funny current): 1) Na+ inward current (first) 2) Ca2+ inward current (later) 0 3 4 Summary Electrocardiogram (ECG) Electrocardiogram (ECG): Electrical Activity of the Heart P-Wave – atria depolarise QRS- wave – ventricles depolarize, (atria repolarize) T-wave – ventricles repolarise https://doctorlib.info/physiology/ganong-review-medical-physiology/ganong-review- medical-physiology.files/image594.jpg  ECG Information Gained (Non-invasive) Heart Rate Signal conduction Heart tissue Conditions onship between Pressure, Volume and ECG (Wiggers Diagram) EDV = End Diastolic Volume ESV = End Systolic Volume https://i2.wp.com/biologydictionary.ne t/wp-content/uploads/2017/02/Cardia c-Cycle-Animated-683x1024.gif https://ecgwaves.com/wp-content/uploads/2019/12/ventricular-pressure-volume- relationship-stroke-volume-diastole-systole-1-1536x1421.jpg  Cardiovascular Physiology Cardiac Cycle 19.3 Cardiac Cycle – Anatomy & Physiology (oregonstate.education) Summary Role of cardiovascular system Main Structures Including Chambers, valves, major blood vessels Electrophysiology Types of cell and action potentials (ion changes) Electrical excitation coupling ECG Pressure changes and cardiac cycle The Blood Vessels and the Cardiovascular System Arteries: blood from heart Strong & Elastic Conduct blood to capillaries Capillaries: exchange with cells Veins Return blood to heart Valves The Blood Vessels and the Cardiovascular System Arteries endothelium Smooth muscle cell layer adventitia Veins “Blood Reservoir” 70% of our blood volume is on the venous side. Composition of the vessels All blood vessels, except capillaries, have three tissue layers: Inner layer: Tunica interna (intima) Middle layer: Tunica media Outer layer: tunica externa  Composition of the vessels Tunica Intima Innermost layer of vessels (tunica interna) Composed of: 1) Endothelial cells. Controls contractility –secreting endothelial factors (paracrine) that mediate contraction/dilatation 2) Basement Membrane separates the tunica intima from the tunica media 3) In arteries, a layer of elastic tissue called the internal elastic lamina (allows distension when high pressure blood is ejected from the ventricles)  Composition of the vessels Tunica Media Middle layer - Usually the thickest. Composed of: Smooth Muscle Cells- maintains a partial contraction (sets vascular tone). Contraction triggered by Ca2+ entry. Paracrine regulation of their contraction/relaxatio n by the endothelial cells Gap junctions (transmission of action potentials) Composition of the vessels Tunica Externa Outermost layer (also known as tunica adventitia). Composed of: Collagen and Elastin fibres elastic tissue (external elastic lamina). Vasa vasorum (vessels of the vessel): capillaries in large arteries and veins that provide oxygen and nutrients to the cells in the tunica externa 46 Make Up of Blood Vessels: Arteries and Arterioles 1. Arteries: Carry blood away from the heart towards the organs. Regulation of arterial blood pressure (MAP). -Endothelium, Elastic tissue, Smooth muscle, Fibrous tissue. 2. Arterioles: Small vessels that carry blood from arteries to capillaries. Also help to maintain blood pressure. Responsible for most of peripheral resistance. -Endothelium, Elastic tissue, Smooth muscle, fibrous tissue. 3. Capillaries: Microscopic vessels that connect arterioles to venules. Control blood distribution to organs. Monolayer- Exchange Nutrients -Endothelium, Elastic tissue, Smooth muscle, fibrous tissue. 4. Venules: Small vessels that drain blood from capillaries into veins. -Endothelium, Elastic tissue, Smooth muscle, fibrous tissue. 5. Veins: Carry blood from venules to the heart. Blood Constituents Red Blood Cells Erythrocytes Concave shaped cells Anucleated Contain Haemoglobin Most abundant cells in body Account for 40-45% of blood volume Develop in bone marrow Last 120 days then broken down and recycled by macrophages Haemoglobin Protein responsible for transporting oxygen in the blood of vertebrates Comprises four subunits (2 alpha and 2 beta) Each subunit contains an iron atom bound to a haem group Each haem can bind an oxygen molecule Haemoglobin exists in Tense and Relaxed forms Tense form – low affinity for oxygen Oxygen binding transforms Hb to the relaxed state Relaxed state = high affinity for oxygen Contin Educ Anaesth Crit Care Pain, Volume 12, Issue 5, October 2012, Pages 251–256, https://doi.org/10.1093/bjaceaccp/mks025 The content of this slide may be subject to copyright: please see the slide notes for details.  The Oxyhaemoglobin Dissociation Curve DPG = diphosphoglyceric acid Contin Educ Anaesth Crit Care Pain, Volume 12, Issue 5, October 2012, Pages 251–256, https://doi.org/10.1093/bjaceaccp/mks025 The content of this slide may be subject to copyright: please see the slide notes for details. Respiration and Gas Exchange Carbon Dioxide Transport Carbon dioxide is transported in the blood in three forms Bicarbonate major. ~85% In solution ~ 5% Bound to Hb Erythropoetin and RBC Production Glycoprotein hormone secreted by the kidneys(liver important in fetal stage) Increases the rate of production of red blood cells in response to falling levels of oxygen in the tissues aemoglobin Breakdown and Bilirubin creased Bilirubin = Jaundice Anaemia Iron deficiency anaemia – diet/haemorrhage Thalassemia – genetic disorder; alpha or beta forms (Alpha or beta globulin absent/faulty) Aplastic anaemia Sickle cell anaemia Vitamin deficiency anaemia – pernicious anaemia Aplastic Anaemia Body does not produce blood cells Causes: Autoimmune disorders Toxic substances Chemotherapy Viral infection Certain medications including some antibiotics Cancer that affects has spread to the bone marrow Inherited conditions Sickle Cell Disease A group of inherited conditions of sickle haemoglobin. abnormal beta-globin chain which causes it to polymerize when deoxygenated distorting the erythrocyte into a sickle shape Pernicious Anaemia White Blood Cells 1% of blood volume immune cells that helps our body to fight against infections Types Granulocyte: WBCs with granules in their cytoplasm neutrophil, eosinophil, and basophil. Agranulocytes: WBCs with no distinct granules in their cytoplasm. monocyte (macrophages) and lymphocyte. Plasma Proteins Numerous Albumin - major Alpha1 acid glycoprotein Clotting factors – proenzymes Hormones Vasoactive peptides etc…. Blood Clotting Clot Formation Platelet Activation Platelets activated by ADP Thromboxane A2 Thrombin Serotonin Summary