Heart and Cardiac Physiology Nestor T. Hilvano, M.D., M.P.H.

Learning Objectives 1.Describe the location and gross anatomy of the heart noting the chambers and heart valves. 2.Describe the pericardium and its functions. 3.Identify the layers of the heart. 4.Trace the flow of blood through the heart. 5.Discuss the blood supply to the heart. 6.Describe the components and functions of the conducting system of the heart. 7.Identify the electrical events associated with a normal ECG. 8.Explain the events of cardiac cycle and relate the heart sounds to specific events in the cycle. 9.Define the cardiac output, heart rate, and stroke volume and describe the factors that influence these variables.

Overview of Cardiovascular System Two major divisions: Pulmonary circuit - right side of heart –carries blood to _____________ Systemic circuit – left side of heart –supplies blood to _____________ a.Different organs of the body b.Lungs

Location and Position of Heart Located in ________, between lungs ____ = at 3 rd costal cartilage ____ = at 5 th ICSLMCL weighs 10 oz Study the external and internal anatomy of the heart in textbook/web references a.Base b.Apex c.Mediastinum

Pericardium Pericardium - double lining of pericardial cavity _____ - outer, tough, fibrous layer. ____ - inner, thin, moist, serous layer. Pericardial cavity –filled with _____, w/c functions to _______. Pericardiocentesis - drainage of fluid- left 5 th or 6 th ICS near the sternum a.Visceral pericardium (epicardium) b.Parietal pericardium

Heart Wall _______ - outer layer, covers the heart _______ - middle, muscular layer; with fibrous skeleton (network of collagen & elastic fibers) _______ - inner layer, simple squamous epithelium a.Endocardium b.Epicardium (visceral pericardium) c.Myocardium

Heart Chambers Name the 4 heart chambers: RA, LA, RV, LV Interatrial septum R and L Atria: Pectinate muscles, Sinus Venarum, Fossa ovalis* (RA only), Coronary sinus* (RA only) Interventricular septum R and L Ventricles: Trabeculae carneae, Chorda tendinae, Papillary muscle, and Moderator band** (RV only – ridge contains part of conducting system) Why is the left ventricle more muscular than the right ventricle?

Heart Valves Atrioventricular (AV) valves –right AV valve: Tricuspid –left AV valve: Bicuspid Semilunar valves – control flow into great arteries –________ to pulmonary circulation –________ to systemic circulation ____ What prevents backflow of blood from the ventricles to the atria during ventricular contraction? a. aortic valve b. pulmonic valve c. closure of AV valves d. closure of semilunar valves

Blood Flow & Coronary Vessels Trace the blood flow from the suprior vena cavae and inferior vena cavae to the pulmonic circulation and systemic circulation. Left coronary artery (LCA) = anterior interventricular branch and circumflex branch Right coronary artery (RCA) = right marginal branch and posterior interventricular branch Great cardiac vein, middle cardiac vein, posterior cardiac vein, and coronary sinus ______ – chest pain due to ischemia, triggered by exertion/stress; relieved at rest. ______ – chest pain persist even at rest (CAD), cell necrosis a. Myocardial infarction b. Angina pectoris

Cardiac Conduction System ____ - pacemaker, initiates heartbeat (sets HR), near the entrance of SVC, 50 msec to travel ____ - electrical gateway to ventricles, near the opening of coronary sinus, delay at 100 msec ____- pathway for signals from AV node ____- divisions of AV bundle that enter IVSeptum ____- upward from apex spread throughout ventricular myocardium a. SA node b. AV node c. Bundle of His d. R and L bundle branches e. purkinje fibers How would the heart rate be affected if the SA node failed to function?

Cardiac Rhythm ____ – contraction ____ – relaxation Sinus rhythm – a regular heart beat –set by SA node at 60 – 100 bpm –adult at rest is 70 to 80 bpm ____ - abnormal cardiac rhythm (irregular heart beat) ____- abnormal heart sounds Heart block - failure of conduction system a. Diastole b. systole c. arrythmia d. murmur

Electrocardiogram (ECG) ____ wave- SA node fires, atrial depolarization ____ complex- ventricular depolarization –Enlarged heart can cause an increase in size of QRS complex ____ wave- ventricular repolarization Sinus rhythm- normal a.P wave b.QRS complex c.T wave

Abnormal ECG Nodal rhythm- no SA node activity PVC (Premature ventricular contraction)- note inverted QRS, misshapen QRS and T and absence of a P wave preceding this contraction Heart Block (Arrhythmia)- conduction failure at AV node Ventricular fibrillation- no pumping action occurs

Heart Sounds First heart sound (S 1 ), louder and longer “lubb”, occurs with closure of AV valves Second heart sound (S 2 ), softer and sharper “dupp” occurs with closure of semilunar valves S3 & S4 – soft sounds, blood flow into ventricles and atrial contraction

Major Events of Cardiac Cycle Cardiac cycle - period between the start of one heartbeat and the beginning of the next Include contraction and relaxation Heart murmur – sounds produced by regurgitation through the valves

Cardio dynamics Cardiac Output - amount of blood ejected by ventricle in 1 minute CO = HR X SV; about 4 – 6 L/min. at rest if HR is 75 bpm and the SV is 80 ml. per beat, the CO will be 6000 ml./min. (6L/min.) SV= EDV – ESV (end-diastolic volume – end-systolic volume) HR = heart rate (beats/min) Pulse - surge of pressure in artery Tachycardia- resting adult HR above 100 Bradycardia- resting adult HR < 60 What is the effect of drinking caffeinated drinks on the heart?

Factors affecting the Heart Rate Autonomic innervations - cardiac center of medulla oblongata - cardiac reflexes = baroreceptors; chemoreceptors Hormones –TH  adrenergic receptors in heart,  sensitivity to sympathetic stimulation,  HR Stroke volume - governed by three factors: 1.preload 2.contractility 3.afterload –  preload or contractility causes  SV –  afterload causes  SV

Homework (Self-Review) 1.Define terms: angina pectoris, myocardial infarction, bradycardia, tachycardia, cardiac cycle, arrhythmia, ECG, cardiac output, stroke volume, pulse, SA node, systole, diastole, parietal pericardium, visceral pericardium, sinus rhythm, moderator band, papillary muscles, pectinate muscles, and fossa ovalis. 2.Describe the walls (layers) of the heart. 3.Identify and describe the P wave, QRS complex, and T wave of ECG tracing. 4.Trace the blood flow starting from right atrium via the superior and inferior vena cava.

“Keep working with a GOOD HEART.” nthmd