Cardiovascular Physiology (Chapter-I) PDF

CARDIOVASCULAR SYSTEM PHYSIOLOGY CHAPTER I: CARDIAC EXCITATION Asst. Prof. Dr. İmge Kunter EMU Faculty of Pharmacy  MAIN TOPICS 1. ANATOMY OF THE HEART 2. CIRCULATIONS 3. SEQUENCING CONTRACTIONS 4. REGULATION of HEART RATE 5. REGULATION of AV NODE CONDUCTION VEL...

CARDIOVASCULAR SYSTEM PHYSIOLOGY CHAPTER I: CARDIAC EXCITATION Asst. Prof. Dr. İmge Kunter EMU Faculty of Pharmacy  MAIN TOPICS 1. ANATOMY OF THE HEART 2. CIRCULATIONS 3. SEQUENCING CONTRACTIONS 4. REGULATION of HEART RATE 5. REGULATION of AV NODE CONDUCTION VELOCITY 6. ELECTROCARDIOGRAPY (ECG)  The Cardiovascular System: Moving Blood through the Body Focus: The cardiovascular system is built to rapidly transport blood to every living cell in the body. The Heart: A Double Pump Focus: In a lifetime of 70 years, the human heart beats 2.5 billion times. This durable pump is the centerpiece of the cardiovascular system.  Heart’s position in thorax 250-350 gm 6  The Heart Composed of myocardium – Cardiac muscular middle layer Protected by the pericardium – Outermost layer Smooth lining of endocardium – Inner layer The Cardiovascular System Helps Maintain Favorable Operating Conditions  Blood Circulation Is Essential to Maintain Homeostasis Major role in homeostasis – brings oxygen, nutrients, and hormones to cells – removes waste products from cells and excess heat  *right atrium and ventricle right heart *left atrium and ventricle left heart  Atriums----- recives the blood – Heart’s Entryways for Blood Ventricles----- push the blood away from heart – Each Heart Beat Is a Squeeze of Two Chambers Called Ventricles  Chambers of the heart sides are labeled in reference to the patient facing you Two atria – Right atrium – Left atrium -------------------------------------------------------------------------------- Two ventricles – Right ventricle – Left ventricle 14 The heart=a muscular double pump with 2 functions Overview Right -- oxygen-poor blood Pumps it to the lungs to exchange 15 The heart=a muscular double pump with 2 functions Overview Left side-- oxygenated blood Pumps this blood throughout the body 16  Valves at the The Heart Valves:  Valves at the The Heart *A heart valve normally allows blood to flow in only one direction through the heart. *A heart valve opens or closes depends on differential blood pressure on each side  Valves at the The Heart Valves: – Atrioventricular: between the upper atria - - the lower ventricles – Semilunar in the arteries leaving the heart.  The Heart Has Two Types Valves – Atrioventricular Valves : Tricuspid (right side) Bicuspid (left side) – Semilunar Valves aortic valve pulmonary valve (in the arteries leaving) A heart valve normally allows blood to flow in only one direction through the heart. A heart valve opens or closes upon Valves (cusp means flap) differential blood three tricuspid pressure on each side one bicuspid “Tricuspid” valve – RA to RV Atrioventricular Mitral valve (the bicuspid one) – LA to LV Aortic valve – LV to aorta Semilunar Pulmonary valve – RV to pulmonary trunk (branches R and L) 25 Blood is prevented from flowing backwards (regurgitation) by the tricuspid, bicuspid, aortic, and pulmonary valves. Left side-- oxygenated blood Pumps this blood throughout the body Function of AV valves 29 Function of semilunar valves (Aortic and pulmonic valves) 30  Note positions of valves Valves open and close in response to pressure differences 33  Two circulations – Systemic circuit: blood vessels that transport blood to and from all the body tissues – Pulmonary circuit: blood vessels that carry blood to and from the lungs 34  PC: moves blood between the heart and the lungs. – It transports deoxygenated blood to the lungs to absorb oxygen and release carbon dioxide. – The oxygenated blood then flows back to the heart. SC moves blood between the heart and the rest of the body. It sends oxygenated blood out to cells and returns deoxygenated blood to the heart. Each Half of the Heart Pumps Blood in a Different Circuit Overview of Pulmonary Circulation  Pulmonary circulations Pulmonary arteries brings O2-poor blood from the right ventricle to the lung. Pulmonary veins carry O2-rich blood to the left side of the heart for delivery to the systemic circulation. Overview of Pulmonary Circulation Deoxygenated blood 5 liters of deoxygenated blood are pumped to the lungs each minute CO2 blood concentration is higher than O2 blood concentration in: – Systemic veins – Right atrium – Right ventricle – Pulmonary arteries Overview of Pulmonary Circulation Oxygenated blood Transported from the pulmonary capillaries → pulmonary veins → left atrium → left ventricle → aorta → systemic arterial circulation O2 blood concentration is higher than CO2 blood concentration in: – Alveoli – Pulmonary capillaries – Pulmonary veins – Left atrium – Left ventricle – Systemic arteries Can the heart beat by itself ? Autorhythm The heart can beat on its own without the need for exogenous commands.  Conclusion ? The heart generates electricity. Motor nerve Skeletal muscle How Cardiac Muscle Contracts Focus: Unlike skeletal muscle, which contracts only when orders arrive from the nervous system, cardiac muscle contracts— and the heart beats– spontaneously. Intercalated Discs Form Communication Junctions between Cardiac Muscle Cells Intercalated discs are complex adhering structures that connect the single cardiomyocytes to an electrochemical sinsitiyum (common cytoplasm a lots of nucleus, fused cells)  Intercalated Discs adherens junctions desmosomes gap junctions. Figure 18.12c, d  Cardiac Muscle Cells: Myocardial Autorhythmic Cells – Membrane potential “never rests” pacemaker potential. Myocardial Contractile Cells – Have a different action potential due to calcium channels. General cardiac cell stuff – Intercalated discs – Gap Junctions (instead of synapses) – Many mitochondria Figure 14-10: Cardiac muscle  cardiac muscle cell cardiomyocytes (99%) (Contract easily) – Respond to impulses of action potential from the pacemaker ceels – Responsible for the contractions that pump blood through the body. pacemaker cells (1% (modified cardiomyocytes - conduction system)  cardiac muscle cell cardiomyocytes (99%) (Contract easily) pacemaker cells (1% (modified cardiomyocytes - conduction system) – Have limited contractibility – Their function is similar in many respects to neurons – The bundle of His and Purkinje fibres are specialised cardiomyocytes that function in the conduction system.  Conducting System Intrinsic ability to generate and conduct impulses (rhythmically/do not depend on nerve impulses) This autorhythmicity is still modulated by endocrine and nervous systems. Components include the: sinoatrial node internodal fibers AV node AV bundle Bundle branches Purkinje fibers Electrical Signals from “Pacemaker” Cells Drive the Heart’s Contractions Cardiac conduction system – Independent of the somatic nervous system – (autorhythmicity)-ability to initiate a cardiac action potential-fixed rate – Spreading the impulse – Rhythmical impulses created by pacemaker cells – Control the heart rate  Cardiac conduction system – Sinoatrial (SA) node: 100 beats/minute – Atrioventricular (AV) node: 40-60 beats/minute  Cardiac conduction system – Sinoatrial (SA) node: – impulse-generating (pacemaker) tissue – located in the right atrium – Generate normal sinus rhythm – Atrioventricular (AV) node: – Coordinates the top of the heart – It electrically connects atrial and ventricular chambers. – Located between the atria and the ventricles of the heart  Sequencing Contractions SA node is called the pacemaker of the heart SA node is composed of a group of specialized cardiac muscle cells Instead they are the cells that gained a property to generate spontaneous action potentials.  Atrial excitation Once the action potential is initiated in SA node, the depolarization wave spreads outward in all directions and covers all the atrial muscle cells.  AV node The spreading wave of depolarization reaches to AV node before it reaches to the ventricles. AV node has of non-contractile cardiomyocytes specialized to conduct signals slowly- electrical insulator. This also protects the ventricles from excessively fast rate response to atrial arrhythmias It allows blood to move from atria to ventricles.  VENTRICULAR EXCITATION This pathway to the ventricles begins with the common bundle of His a tract of specialized myocytes Here it separates into left and right bundle branches High-speed Purkinje fibers carry the depolarization wave to the ventricular cardiac muscle cells. Conduction system Contraction begins at apex SA node (sinoatrial) – In wall of RA – Sets basic rate: 70-80 (upto 1000) – Is the normal pacemaker Impulse from SA to atria Impulse also to AV node via internodal pathway SA node through AV bundle (bundle of His) – Into interventricular septum – Purkinje fibers 63  Heart rate (HR) Heart rate (HR) can be called as; the rate at which action potentials are initiated in SA node Heart rate, is the speed of the heartbeat measured typically beats per minute (bpm) Definition: a single sequence of atrial contraction followed by ventricular contraction  Heartbeat Systole - contraction of a heart chamber Diastole (‘expansion’) – when a heart chamber relaxes and fills with blood Normal rate: 60-100 Slow: bradycardia Fast: tachycardia 65 The Heart Beats in a Sequence Called the Cardiac Cycle  Heart rate (HR) HR is under control of autonomic nervous system Sympathetic nervous system Parasympathetic nervous system HR HR  CHRONOTROPY Positive chronotropy is used for increased heart rate Negative chronotropy is used for reduction in heart rate  REGULATION of SA NODE PARASYMPATHETIC NS ACETYLCHOLINE EPINEPHRINE M2 receptors β – 1 adrenergic receptors cAMP cAMP (-) chronotropy (+) chronotropy Decreased HR Increased HR Modulation of Contraction- what is the key ion? Figure 14-12: Modulation of cardiac contraction by catecholamines  DROMOTROPY The term “dromotropy” is used to define the conduction speed in AV node. (+) dromotropy SYMPATHETIC Increased rate of conduction through the AV node NS (-) dromotropy PARASYMPATHETIC NS Decreased rate of conduction through the AV node ELECTROCARDIOGRAPHY  Arrhythmias Are Abnormal Heart Rhythms Electrocardiogram (ECG) – Recording of the electrical activity of the cardiac cycle Arrhythmias: irregular heart rhythms – Bradycardia: slower than normal heart rate – Tachycardia: faster than normal heart rate – Ventricular fibrillation: rapid, erratic electrical impulses  ELECTROCARDIOGRAPHY ECG captures a series of snapshots of these electrical events to provide information about their timing, direction and the mass of tissues involved. Waves in the ECG recording are created by excitation and recovery of different regions of the heart. 75  P wave P wave: When the wave of depolarization spreads across the atria, P wave is recorded in ECG. P wave refers the atrial excitation (atrial depolarization).  QRS complex QRS complex: Ventricular depolarization produces the QRS complex QRS complex refers the ventricular excitation. Components: a) Q wave: Excitation of interventricular septum, b) R wave: the apex and the free walls c) S wave: regions the base  T wave T wave: Ventricular repolarization registers on the ECG recording as the T wave. (ventricular recovery) ELECTROCARDIOGRAPHY  ELECTROCARDIOGRAPHY HEIGHT amount of muscle involved INTERVALS duration of electrical event ELECTROCARDIOGRAPHY  Why it is important to understand these things? In pharmacology QRS duration PR interval QT interval THE END  http://learn.visiblebody.com/circulatory/circul atory-diseases-and-disorders