Cardiovascular System Chapter 11 Conduction System Intrinsic conduction

Cardiovascular System Chapter 11

Conduction System • Intrinsic conduction system (nodal system) • Heart muscle cells contract, without nerve impulses!

Conduction System • Sinoatrial node = SA node (“pacemaker”) • right atrium

Conduction System • Atrioventricular node = AV node • junction of the right atrium and right ventricle

Conduction System • Atrioventricular bundle = AV bundle (bundle of His) • In the interventricular septum • Bundle branches • Purkinje fibers (ventricle wall muscles)

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 • “wringing” contraction – begins at apex, moves toward atria • Blood ejected

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

• https: //www. youtube. com/watch? v=T 4 x 7 -2 HKt. J 0 • https: //www. youtube. com/watch? v=o. HMmtq. Kgs 50 • https: //www. youtube. com/watch? v=qmpd 82 mp. VO 4

• 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