Transcript document
The Heart CARDIAC CIRCULATION Objectives 1. Identify the structures of the heart. 2. Describe the path of blood through the heart. 3. Describe the pulmonary and systemic circuits THREE CIRCULATORY SYSTEMS - There are 3 circulatory systems in your body 1) Systemic - delivers blood between the heart and body cells (we have covered this… Describe..) 2) Cardiac - circulation of blood in the heart 3) Pulmonary - blood goes to the lungs to be oxygenated - delivers blood between the heart and the lungs Systemic circulation: heart oxygenated blood artery arterioles capillaries (half blue) gas exchange venuoles deoxygenated blood veins heart • The mammalian heart is a double pump, separated by a wall of muscles called a septum This section of the system including the right side of the heart, deals with the deoxygenated blood. Lungs Body cells This section of the system including the left side of the heart, deals with the oxygenated blood. Each side of the heart is divided into two chambers: an upper atrium and a lower ventricle (four chambers in total) The interior of the heart has: •4 chambers – two atria (top chambers) - two ventricles (bottom chambers) •4 valves – two atrio-ventricular valves - two semi–lunar valves •Septum – a wall • It is used to push blood through the body and provides a connection between our pulmonary and systemic circulatory systems • The heart is supplied by blood via the coronary arteries (come off main aorta) Refer to your heart diagram as we move through the lesson…. You should be able to label it by the end! The two top chambers are called the right atrium and the left atrium. Atria are thin-walled and flexible allowing for easy filling or collecting of blood The two bottom chambers are called the right ventricle and the left ventricle. Ventricles are thick-walled and strong enough to pump blood out of the heart. The left ventricle is the most muscular chamber of the heart. The two atrio-ventricular valves lie between the atria and the ventricles. R ◦ Right it is called the tricuspid valve ◦ Left it is called the bicuspid valve. The two semi-lunar valves lie between the ventricles and their attached vessels. They are called the right and left semi-lunar valves. A wall that separates the heart into a right side and a left side. This ensures that blood in each side of the heart stays in that side of the heart. Two Pumps The right pump on the right side of the heart, collects or fills with deoxygenated blood coming back from the body by way of veins and then pumps it to the lungs The left pump on the left side of the heart, collects or fills with oxygenated blood coming from the lungs and pumps it into the body by way of arteries There are 4 main vessels that are responsible for bringing blood into the heart and out of the heart Right Side – the superior and inferior vena cava bring deoxygenated blood from the body into the right atrium; two pulmonary arteries carry this deoxygenated blood away from the heart and into the right and left lung. Left Side – the pulmonary veins carry oxygenated blood from the right and left lung towards the left atrium of the heart; the aorta carries this oxygenated blood away from the left ventricle of the heart to the body • http://www.fed.cuhk.edu.hk/~johnson/teac hing/transport/animations/HyperHeart.swf • http://www.mayoclinic.com/health/circulato ry-system/MM00636 • http://www.nhlbi.nih.gov/health/dci/Diseas es/hhw/hhw_pumping.html Your Task 1. Label your diagram of the heart. This could appear on the test. 2. On your second heart, trace the path of blood as it enters the heart on its way to the lungs and then back from the lungs to the body. 1. Use colour to represent oxygenated and deoxygenated blood. 3. Answer questions 1-4 on page 258 of your text. OVERALL CARDIAC CIRCULATION deoxygenated blood is collected from your upper body through the superior vena cava from your lower body through the inferior vena cava right atrium (through atrioventricular tricuspid valve) right ventricle (through semilunar valve) right pulmonary artery left pulmonary artery Pulmonary Circuit left lung right lung capillaries -> CO2 exchanged for O2 through simple diffusion pulmonary veins left atrium (through atrioventricular bicuspid valve) left ventricle (through semilunar valve) arteries arterioles aorta veins venules capillaries (O2 is dropped off, CO2 is picked up) Plenary 1. Trace the path of blood through the heart. 2. What is the function of A-V and Semi lunar valves 3. What is different about the pulmonary arteries and veins Control of the Heartbeat Objectives: 1. Describe the sequence of events involved in the heart contracting. 2. Explain what intrinsic and extrinsic control is 3. Explain what pulse and blood pressure is and how it is measured. Heart Beat • • • • • • • • • Each heartbeat is called a cardiac cycle On average the heart beats 72 b/minute Each heartbeat lasts 0.85 seconds Systole refers to the contraction of the heart Diastole refers to the relaxation of the heart One heartbeat consists of the following: Two atria contract Two ventricles contract Four chambers relax Heart Sounds • These are sounds produced by the heart caused mainly by the vibrations produced when the heart valves close and the blood bounces back against the walls of the ventricles or blood vessels ‘LUB – DUB’ First Heart Sound ◦ is the beginning of systole ◦ the sound is a longer and lower pitched ‘lub’ ◦ it is caused by vibrations occurring when the A-V valves close due to the pressure of the ventricles filling with blood from atria Second Heart Sound ◦ this sound occurs at the end of systole and the beginning of diastole ◦ the sound produced is a shorter and sharper pitched ‘dub’ ◦ Atria are relaxed and fill with blood ◦ it is caused by vibrations occurring when the semi-lunar valves close preventing blood from re-entering the ventricles Stethoscope is a diagnostic tool used to help determine heart sounds of systole and diastole (TRY LISTENING to your partners heart!!) HEART MURMUR • Slush sound after the ‘lub’ heart sound that may be caused by faulty valves, in particular the A-V valves, allowing blood to back flow into the atria from the ventricles. • Rheumatic fever may be a cause of faulty valves • faulty valves can be surgically corrected INTRINSIC Control of the Heartbeat Intrinsic Control– internal (inside) control of the heartbeat The intrinsic conduction system of the heart is responsible for the rhythmical contraction of the heart There are four structures that form this system. They are: i) SA node ii) AV node iii) AV bundle iv) Purkinje fibres Nodal tissue is a unique muscle tissue of the heart It has properties of both muscle and nervous tissue Nodal tissue is located in two areas of the heart: i) the upper dorsal (back) wall of the right atrium (SA node) ii) the base of the right atrium near the septum (AV node) SA NODE • Sinoatrial node sets the heart’s tempo or beat rate • Also called the pacemaker • Initiates the heartbeat and automatically sends out an excitation impulse every 0.85 seconds causing atria to contract • NOTE: when the SA node malfunctions the heart still beats due to AV nodal tissue but the beat is slower. This is corrected by inserting an artificial pacemaker. A-V NODE • Atrio-ventricular node • Upon completion of contraction of the atria the A-V node sends an impulse through the A-V bundle which then passes the impulse onto Purkinje fibres found throughout the periphery of the ventricles causing them to contract. SA and AV nodes Sequence of Contraction 1. SA node initiates an impulse causing both atria to contract 2. Both atria contract forcing blood into each ventricle 3. AV node sends impulse onto A-V bundle to the Purkinje fibres triggering the contraction of both ventricles 4. Both ventricles contract and force blood into both arteries (on the right side of the heart the pulmonary arteries receive the blood and on the left side of the heart the aorta receives the blood) 5. Heart relaxes allowing the atria to fill with blood SA and AV nodes EXTRINSIC Control of the Heartbeat There are two factors involved in outside control of the heart. They are the medulla oblongata in the brainstem and hormones The autonomic nervous system has 2 divisions, the sympathetic and parasympathetic The sympathetic system, when activated, increases the heart rate as directed by the medulla oblongata The parasympathetic system, when activated, decreases the heart rate as directed by the medulla oblongata The hormones epinephrine and norepinephrine, released by the adrenal medulla, will also increase heart rate. The medulla contains cardiac and respiratory centers that play a role in involuntary functions, such as breathing, heart rate and blood pressure. The hormones epinephrine and norepinephrine, released by the adrenal medulla, will also increase heart rate. Epinephrine and norepinephrine also produce fight or flight responses such as increasing heart rate and increasing blood flow to skeleton muscles … to run away. ECG is a recording of electrical changes that occur in myocardium during a cardiac cycle (one heartbeat) P wave – occurs just prior to atrial contraction QRS wave – occurs just prior to ventricular contraction T wave – occurs when the ventricles are recovering from contraction The purpose of an ECG is to detect various types of abnormalities in the beating of the heart Your Task 1. Read the handouts on the Circulatory System and Blood Vessels and answer the questions. Plenary 1. What does systole and diastole mean? 2. What causes the ‘Lub’ ‘Dub’ sounds your heart makes? 3. What is the ‘pacemaker’ of your heart and why is it called this? 4. Describe the sequence of events involved in the heart contracting. 5. Explain what intrinsic and extrinsic control is 6. What is a heart murmur. 7. What happens during systole and diastole? Measuring Pulse and Blood Pressure Objectives is caused by the rhythmical expansion and recoil of the arterial walls as blood passes through the artery it can be felt (palpated) in any artery close to the body’s surface the two most common sites to check for a pulse are the radial artery and the carotid artery the pulse is used in place of a direct measurement of heart rate. It is an estimation of heart rate Pulse Points Is the pressure or force that blood exerts against the wall of a vessel The aorta is under the highest pressure of all the vessels and BP is lowest in the vena cava Blood pressure is the greatest in arteries, less in capillaries and negligible in veins The further away form the heart the vessel is, the less pressure the vessel is under Systolic pressure is the highest arterial pressure reached during ejection of blood from the heart (ventricular contraction) Diastolic pressure is the lowest arterial pressure measured while the heart ventricles are relaxing Normal resting BP is 120/80 mmHg at the site of the brachial artery BP in venules and veins is negligible Venous return of blood is dependent upon the following three factors: Skeletal muscle contraction Valves in the veins Respiratory movements Skeletal muscle contraction moving blood in veins SPHYGMOMANOMETER is a blood pressure cuff is a diagnostic tool for measuring BP usually used to measure BP at the brachial artery HYPERTENSION Is a condition that occurs when arterial BP is significantly above average most of the time (at least 140/90 mmHg) If not treated it can cause cerebral hemorrhage (stroke) or heart failure Blood pressure accounts for the flow of blood in the arteries and the arterioles Skeletal muscle contraction, valves in veins and respiratory movements account for the flow of blood in the venules and the veins Blood velocity gradually decreases further away from the heart as blood pressure decreases Blood velocity is greatest in arteries, less in arterioles, very slow in capillaries, increases slightly in venules and veins 1. Answer Questions 2. P.263 #1,2,3, 5, 6,7 3. H/W Read about Disorders of the Circulatory System. 4. Make study notes to help you remember at least … • 1 disorder that is associated with the heart • 1 disorder that is associated with the blood • 1 disorder that is associated with the blood vessels. 1. 2. 3. 4. 5. Explain what pulse and blood pressure is and how it is measured. What factors affect heart rate and blood pressure? How can we determine if these factors are having an effect on heart rate and blood pressure? When designing an experiment, why is it important to only change one variable? How can you ensure that your investigation is a fair test?