Introduction to Cardiac Physiology PDF

Introduction to cardiovascular physiology Presented by Dr. Sherif Diaaeldin Assistant Professor of Physiology  Functional anatomy of the heart The heart is a hollow muscular organ surrounded by a connective tissue sac called the pericardium. The pericardium protects the heart...

Introduction to cardiovascular physiology Presented by Dr. Sherif Diaaeldin Assistant Professor of Physiology  Functional anatomy of the heart The heart is a hollow muscular organ surrounded by a connective tissue sac called the pericardium. The pericardium protects the heart and allows its contraction with minimal friction. The wall of the heart is made of cardiac muscle, and it is divided into right and left Right atrium halves, each of which and right consists of one atrium and ventricle one ventricle.  The right atrium is separated from the right ventricle by the tricuspid valve, while the left atrium is separated from the left ventricle by the bicuspid (or mitral) valve. Both valves are called the atrioventricular valves (A-V valves) In the ventricles, there are certain muscle called the papillary muscle the tendons of which (called chordae tendinea) are attached to the A-V valves, to prevent eversion into the atria during the ventricular contraction.  The aorta arises from the left ventricle and the aortic opening is guarded by the aortic valve. The pulmonary artery arises from the right ventricle and the pulmonary artery opening is guarded by the pulmonary valve. What is the function of the heart valves? It allows the blood flow in one direction only Divisions of the circulation The systemic circulation The pulmonary circulation This starts from the left This starts from the right ventricle ventricle Aorta Pulmonary artery Arteries lungs Arterioles Pulmonary capillary Capillaries Pulmonary veins (4 in Venules number) Veins Left atrium Superior and inferior venae cava Right atrium  Functions of the atria and ventricles The atria are the entry way to the ventricles. The ventricles pump the blood to the whole body. The aorta pumps oxygenated blood to the whole body. The pulmonary veins delivers oxygenated blood to the heart from the lungs, while pulmonary artery delivers deoxygenated blood to the lungs. Mechanism of heart beating Heart rate 60-90 beat/min average 72 beats/min in adults The impulse originates at the sino-atrial node (found in the right atrium) causes contraction of the atria. Then the impulse reaches the atrioventricular node then the impulse passes to the ventricle through His-purkinje system causing ventricular contraction Factors affecting the heart rate Factors increasing the heart Factors decreasing the heart rate rate Sympathetic stimulation Parasympathetic increases the heart rate e.g., stimulation decreases the in fear and stress. heart rate. Exercise increases the heart Sleep decreases the heart rate. rate. Increase body temperature every degree Celsius Decrease in the body increases the heart rate by 10 temperature decreases the beats/min e.g., fever. heart rate. Thyroxin and adrenalin Drugs e.g., beta blockers. hormones increase heart rate. Heart Sounds  The cardiac cycle The cardiac cycle consists of one systole-diastole sequence It lasts about 0.8 second During atrial systole the blood passes from the atria to the ventricle, while during ventricular systole the blood passes from the ventricle to the lung on the right side and to the whole body on the left side. During atrial diastole the atria receives blood through the superior and inferior vena cava, while during ventricular diastole the ventricles get filled with blood coming from the atria The cardiac output It is the amount of blood pumped by each ventricle per minute (=5.5 L/min). The stroke volume is the amount of blood pumped by each ventricle per beat (about 80 ml/beat). The cardiac output= heart rate X stroke volume Factors affecting the cardiac output Sympathetic stimulation increases the cardiac output while the parasympathetic stimulation decreases it. Catecholamines and thyroxin increases the cardiac output  Blood vessels Types of blood vessels: 1. Elastic arteries. (Windkessel vessels).e.g. Aorta. 2. Muscular arteries.(Conduit vessels).e.g. big arteries. 3. Resistance vessels.e.g. arterioles 4. Exchange vessels. e.g. capillaries Arterial Blood pressure What are the functions of arterial blood pressure 1.Arterial blood pressure is the force which push blood through the circulation to ensure adequate tissue perfusion. 2.Arterial blood pressure is responsible for capillary filtration.  Determinants of arterial blood pressure Physiological variations in arterial blood pressure: 1. Age 2. Sex 3. Diurnal 4. Sleep 5. Emotions 6. Exercise 7. Gravity  Hypertension in man BP> 140/90 in young, > 150/100 up to 50, > 160/100 over 50. Types: 1ry hypertension: 90% of cases, without cause. Characterized by narrow arterioles due to Hyperactivity of vascular system to constrictor stimuli. 2ry hypertension: 10% of cases, due to:- 1-Renal failure 2-Atherosclerosis. 3-endocrine disorders Predisposing factors to hypertension: 1-Smoking 2-obesity 3-excess salt intake  Functions of veins Veins are passageways for blood flow to the heart. They are necessary for proper operation of the circulation. How? Function of Veins:- 1. Drain capillary blood to the heart 2. Blood returned to the heart by veins determine CO Venous return is the volume of blood that enter the right ventricle / minute. It is equal to cardiac output.  Shock & Haemorrhage Hemorrhage is the loss of blood from the cardio- vascular system, it could be :- 1. External 2. Internal , it is dangerous because it is difficult to diagnose. Shock is decreased tissue perfusion so that the amount of oxygen & nutrients reaching the cells is not sufficient to maintain life processes. if the amount of blood loss is less than 20% of total blood volume, it can be compensated but if the amount of blood loss exceeds 20% , compensatory mechanisms are insufficient and death occurs unless blood transfusion is done. Compensatory mechanisms aim at:- increase arterial blood pressure and cardiac output ( immediate compensatory mechanisms). restore blood volume ( delayed compensatory mechanisms).