Cardiovascular System Chapter 11

Conduction System Intrinsic conduction system (nodal system)

Conduction System Sinoatrial node = SA node (“pacemaker”)

Conduction System Atrioventricular node = AV node

Conduction System Atrioventricular bundle = AV bundle (bundle of His) In the interventricular septum

Heart Contractions Contraction is initiated by the SA node Impulse spreads to AV node, atria contract Contraction is delayed Passes through AV bundle, bundle branches and Purkinje fibers

Cardiac Cycle Atria contract simultaneously Atria relax, then ventricles contract Systole = Diastole = Atrial contraction Mid-to-late diastole (ventricular filling) Ventricular systole (atria in diastole) Early diastole Isovolumetric contraction phase Ventricular ejection phase Isovolumetric relaxation Ventricular filling Left atrium Right atrium Left ventricle Right ventricle

“Lub – dub” beat of heart The “ lub” is the first heart sound, commonly termed S1, and is caused by turbulence from the closure of bicuspid (mitral) and tricuspid valves at the start of systole. The second sound,” dub” or S2, is caused by the closure of aortic and pulmonic valves, marking the end of systole.

Cardiac output (CO) Amount of blood pumped by each side (ventricle) of the heart in one minute Stroke volume (SV) Volume of blood pumped by each ventricle in one contraction (each heartbeat) Heart rate (HR) Typically 75 beats per minute CO = SV x HR

Electrocardiogram (ECG or EKG)

Blood Vessels: The Vascular System Arteries Arterioles

Blood Vessels: The Vascular System Capillary beds -

Blood Vessels: The Vascular System Venules Veins

Blood Vessels: The Vascular System

Blood Vessels: Microscopic Anatomy Three layers (tunics)

Blood Vessels: Microscopic Anatomy Tunic intima Tunic media Tunic externa

Differences Between Blood Vessels Walls of arteries are the thickest Lumens of veins are larger

Movement of Blood Most arterial blood is pumped by the heart

Capillary Beds Two types of vessels Vascular shunt— True capillaries—

Capillary Beds