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Transcript
18 The Cardiovascular System: The Heart The Heart Part 1: Heart Anatomy Heart Membranes • pericardium - double-walled sac around the heart fibrous (parietal) pericardium - tough and dense protects the heart anchors it to surrounding structures prevents overfilling of the heart with blood serous (visceral) pericardium - thin and slippery reduces friction • cone-shaped muscular organ about the size of your fist • weighs less than a pound • 2/3 lies to the left of the body's midline • apex (tip) tilted to the left Layers of the Heart Wall • epicardium - external heart surface often infiltrated with fat • myocardium - heart muscle responsible for muscle contraction arranged in spiral and circular bundles • endocardium - a simple squamous epithelium lining the inner surfaces of the heart and blood vessels VS. 18 The Cardiovascular System: The Heart 1 The heart is enclosed in a double membrane sac called the ____. Ping Pong Back & Forth describing the location, membranes, and layers of the heart. 2 Heart muscle is called the ____. Chambers of the Heart • 4 chambers R and L atria on top of R and L ventricles • atria - small, thin-walled chambers that receive blood pumps blood "downstairs" to ventricles • ventricles - large, muscular pumping chambers pumps blood outside of heart • R and L side of heart divided by a septum Atria • right atrium - receives deoxygenated blood through superior vena cava and inferior vena cava passes blood to right ventricles through the tricuspid valve • left atrium - receives oxygenated blood through four pulmonary veins pulmonary = lungs 2 veins from each lung passes blood to left ventricles through bicuspid (mitral) valve Ventricles • papillary muscles and chordea tendinaea play a role in valve function • discharging chambers (pumps) of the heart walls thicker than atria • right ventricle - pumps deoxygenated blood through pulmonary semilunar valve and pulmonary trunk toward the lungs • left ventricle - pumps oxygenated blood through aortic semilunar valve and aorta to all body parts thicker wall than R ventricle 18 The Cardiovascular System: The Heart Body RA Tricuspid RV Lungs High Card Wins...Best 2 out of 3 LA Bicuspid LV RIGHT LEFT low card...what do you know about the structure of the heart so far? High card...fill in the gaps. 4 The ___ side of the heart deals with oxygenated blood. 3 MATA: The receiving chambers of the are the A right atrium B right ventricle C left atrium D left ventricle 5 MATA: The tricuspid valve A is located on the right side of the heart B separates atria from ventricle C touches oxygenated blood D is connected to the pulmonary artery 18 The Cardiovascular System: The Heart Pulmonary Circulation Double Pump • R side of heart handles oxygen poor blood ONLY pulmonary circuit R heart lungs L heart • L side of heart handles oxygen rich blood ONLY systemic circulation L heart body R heart harder work = bigger, stronger structures • circulates blood to lungs • R atrium R ventricle pulmonary arteries pulmonary arterioles pulmonary capillaries CO2 and O2 exchanged pulmonary venules pulmonary veins L atrium • blood travels in 2 distinct loops double pump picks up O2 from lungs drops off O2 to body cells Systemic Circulation • • • • systemic = body systems circulates blood to body aorta - largest artery superior/inferior vena cava largest veins superior - collects blood from head, chest, arms inferior - collects blood from lower body • L ventricles aorta major body regions veins superior/inferior vena cava nonwinner...pulmonary circuit NOSE GOES Winner... systemic circuit 18 The Cardiovascular System: The Heart Path of Blood 6 The ____ circuit carries oxygenated blood to body and returns deoxygenated blood to the right side of the heart. semilunar bicuspid/AV semilunar AV Coronary Circulation • myocardial cells require a continual supply of oxygenated blood • supplied by the coronary arteries branch off of aorta • angina - chest pain · blockage of coronary blood vessels can cause a myocardial infarction (heart attack) Work with your partner to put it all together... chambers, valves, blood flow, layers, membranes... 7 Trace the path of blood through the heart. (Enter as a number. Ex. 12345678) 1- Lungs 2- body 3- pulmonary SL Valve 4- vena cava 5- Left atrium 6- right atrium 7- bicuspid valve 8- aorta 18 The Cardiovascular System: The Heart Cardiac Conduction System • ability of cardiac muscle to depolarize and contract is intrinsic Part 2: Heart Physiology does NOT depend on nervous system composed of autorhythmic cells 1. pacemaker potential SA NOde 2 3 1 2. depolarization no stable resting potential instead, Na+ channels are opened after hyperpolarization allowing potential to drift toward threshold threshold potential = -40mV Ca channels open and Ca rushes into cells 2+ 2+ 3. repolarization K channels open and K rushes out of cell + + Electrical System 1. Sinoatrial (SA) node pacemaker determines heart rate 70-80 per minute 1 2. Atrioventricular (AV) node 4 impulse pauses about 0.1 sec to allow atria to finish contracting 3 3. Atrioventricular (AV) bundle 5 electrical connection between atria and ventricles 4. R and L bundle branches 5. Purkinje fibers 2 highly branched responsible for ventricular contraction 4 Click for animation In a healthy heart, it takes 0.22 sec from SA node stimulation to end of ventricular depolarization! Rock Master...Describe an action potential at the SA Node. Best 2 out of 3 18 The Cardiovascular System: The Heart Nonwinner...Explain how an electrical signal spreads through the heart. 2 Trace the electrical signal through the heart. (Ex. 12345) 1- AV Bundle 2- Bundle branches 3- AV NODE 4- Purkinje Fibers 1 What ion is responsible for pacemaker potential? A sodium B potassium C calcium Changing the Rhythm • cardiac center located in the medulla oblongata sympathetic nervous system speeds up heart rate and force (cardioacceleratory center) parasympathetic nervous system slow down heart rate and force (cardioinhibitory center) • factors that affect heart rate anxiety/stress and activity speed up rate meditation, yoga, sleep slow down rate 5- SA NODE Electrocardiogram (ECG) • aka electrokardiogram (EKG) • recording of the electrical changes in the myocardium • P wave - atrial depolarization Arrhythmias tachycardia quickly followed by atrial contraction • QRS complex - ventricular depolarization quickly followed by ventricular contraction atrial repolarization obscured by QRS complex fibrillation • T wave - ventricular repolarization bradycardia 18 The Cardiovascular System: The Heart together...Make sure you can label each part of an EKG and explain what is happening electrically in the heart. 4 MATA: Which letter(s) represent ventricular depolarization? 3 Name this part of the EKG. Heart Sounds • associated with closing valves • lub-dub, pause, lub-dub, pause, and so on lub - AV valves (tricuspid and bicuspid) close dub - SL valves (pulmonary and aortic) close pause - heart resting between beats A B C D E Cardiac Cycle • aka "heartbeat" • mechanical actions of the heart • each heartbeat (cycle) blood is forced out of ventricles • average adult pumps about 5 L/min • stroke volume - volume of blood pumped by each ventricle per heartbeat • cardiac output - volume of blood pumped per minute by the heart (both ventricles) multiple stroke volume (mm) by heart rate (beats/min) 18 The Cardiovascular System: The Heart Cardiac Cycle (cont.) Cardiac Cycle • systole - contraction of heart muscle • diastole - relaxation of heart muscle • steps 1. atria contract forcing blood into relaxed ventricles (AV valves open, SL valves closed) 2. ventricles contract forcing blood into pulmonary trunk and aorta (AV valves closed; SL valves open) 3. both atria and ventricles relax and atria begin to fill passively with blood (all valves closed) Putting It All Together 5 Heart sounds are caused by A electrical signals travelling the conduction system B valves shutting C blood filling chambers D the heart contracting 18 The Cardiovascular System: The Heart 6 During diastole, the heart muscle relaxes and fills passively with blood. 7 MATA: Stimulation from the AV node A causes the ventricles to contract True B allows the atria to relax False C depolarizes of the ventricles D causes AV valves to open