Cardiovascular System Biology 2122 Chapter 18

Heart Anatomy Location: Mediastinum Coverings (Pericardium) Fibrous and Serous layers Serous (Parietal and Visceral = epicardium) Heart Wall (Layers) Epicardium; Myocardium; Endocardium

Chambers Atria Ventricles Circulation Pectinate muscles; auricles Superior and Inferior Vena Cava Right-side Deoxygenated Blood Coronary sinus/Pulmonary veins Ventricles Trabeculae carneae/Papillary muscles Pulmonary Trunk Aorta Circulation Pulmonary vs. Systemic

Coronary Circulation Arterial – Left Coronary Artery Anterior Interventricular “Left Anterior Descending” Circumflex Arterial – Right Coronary Artery Marginal artery Posterior Interventricular artery Venous Cardiac veins Coronary sinus Great, middle, small cardiac veins Angina pectoris and Myocardial Infarctions

Heart Valves Atrioventricular Valves Semilunar Valves Stenosis Prevents backflow – chordae tendineae Tricuspid (right) Mitral (left) Semilunar Valves Aortic Semilunar Stenosis Heart Animation

Microscopic - Cardiac Tissue Histology Striated Branching Uninucleated Intercalated discs Gap junctions Functional Syncytium High in mitochondria

Cardiac Tissue - Contraction Autorhythmic Cells Heart Contracts as a unit Ion passage through gap junctions Steady and rhythmical waves of depolarization Depolarization Longer absolute refractory periods 250 ms Similar to depolarization events in skeletal muscle Differs in Ca++ release (SR)

Intrinsic Conduction System Sets basic or normal rhythm Autorhythmic Cells Sequence of Excitation SA node (right atria) “pacemaker” Atrioventricular node Above tricuspid valve Atrioventrical bundle “bundle of his” Superior interventricular septum Bundle branches 5. Purkinje fibers Apex Intrinsic Conduction System Animation

Disorders 1. Arrhythmias 2. Fibrillation 3. Heart Block

Extrinsic Innervation and Control Autonomic Nervous System Sympathetic Effects Parasympathetic Effects Cardiac centers Medulla Oblongata Cardioacceleratory Center Sympathetic (T1-T5) Innervate SA and AV nodes Cardioinhibitory Center Vagus Nerve To SA and AV nodes

Electrocardiogram EKG lead placements

Electrocardiography The Electrocardiogram (ECG) Waves P-Wave QRS Depolarization (Atrial contraction) SA node QRS Ventricular depolarization Ventricular contraction T-Wave Ventricular repolarization

Electrocardiography P-Q Interval S-T Segment Q-T Interval

Abnormal ECG Non-functional SA Node Heart Block – Some P-waves not conducted through (see more P-waves)

Heart Sound “Lub-Dub” Lub Dub Heart Murmer AV valve closure SL valves snap shut Ventricular relaxation Heart Murmer

Cardiac Cycle Systole vs diastole The cardiac cycle involves all events associated with blood flow through the heart during one complete heartbeat Ventricular filling: Mid-Late Diastole EDV (end diastole volume) Ventricular Systole ESV (end systolic volume) Isovolumetric Relaxation – Early diastole

Cardiac Cycle Cardiac Cycle Animation

Cardiac Output CO is defined as the amount of blood pumped out by each ventricle in one minute. calculated as the product of stroke volume and rate HR X SV = 5.25 L/min Stroke volume - volume of blood pumped out by one ventricle with each beat CO is variable increases in response to special demands like exercise The difference between resting CO and maximal CO is called cardiac reserve. In trained athletes it is 7 times that of normal (35 L/min)

Stroke Volume Regulation SV is the difference between EDV (blood in ventricle during diastole) and ESV (blood in ventricle during systole) Normal SV = 70 ml/beat Depends on the following factors Preload (Frank-Starling Law) Contractility Afterload

Regulation of Stroke Volume Preload Frank-Starling Law Cardiac muscle cells stretched to optimal length before contraction Contractility Independent of stretch Greater Ca++ influx Increased leads to greater SV Afterload Back pressure on aortic and pulmonary valves Overcome pressure for ventricles to be able to eject blood

Regulation of Heart Rate Autonomic Nervous System 2. Chemical Regulation Hormones (Epinephrine and Thyroxine) Ions Calcium (Hypo- and Hypercalcemia) Potassium (Hypo- and Hyperkalemia) Disorders/Imbalances Tachycardia and Bradycardia 2. Congestive Heart failure