Cardiovascular System Chapter 11

Warm-up Differentiate between Systemic Circulation, Pulmonary Circulation and Coronary Circulation.

Systemic & Pulmonary Circulation

Coronary Circulation

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 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.

https://www.youtube.com/watch?v=T4x7-2HKtJ0 https://www.youtube.com/watch?v=oHMmtqKgs50 https://www.youtube.com/watch?v=qmpd82mpVO4

CO = SV x HR 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

Blood Vessels: The Vascular System Carry blood away from the heart Arteries Arterioles

Blood Vessels: The Vascular System Capillary beds - Exchanges between tissues and blood

Blood Vessels: The Vascular System Return blood toward the heart Venules Veins

Blood Vessels: The Vascular System

Blood Vessels: Microscopic Anatomy Three layers (tunics)

Blood Vessels: Microscopic Anatomy Tunic intima Endothelium Tunic media Smooth muscle Tunic externa Mostly fibrous connective tissue

Differences Between Blood Vessels Walls of arteries are the thickest Lumens of veins are larger Larger veins have valves to prevent backflow Walls of capillaries are only one cell layer thick

Movement of Blood Most arterial blood is pumped by the heart Veins use the “milking” action of muscles to help move blood

Capillary Beds Two types of vessels Vascular shunt—vessel directly connecting an arteriole to a venule True capillaries—exchange vessels

Capillary Beds

Capillary Beds