Features of a good transport system A fluid to carry nutrients and gases A pump to create pressure that will push fluid around the body Exchange surfaces Tubes or vessels – to carry fluid

Pulmonary cirulation – carries blood to the lungs to pick up oxygen Single circulation Double circulation: Pulmonary cirulation – carries blood to the lungs to pick up oxygen Systemic circulation – carries the oxygen and nutrients around the body to tissues. © Pearson Education Ltd 2008 This document may have been altered from the original

Advantages of a Double Circulation Heart increases the pressure on blood after it has passed through the lungs so blood flows more quickly to the body tissues. Systemic circulation can be at a higher pressure than the pulmonary circulation Blood pressure in pulmonary system cannot be too high as it could damage lungs.

PULMONARY ARTERY AORTA PULMONARY VEIN VENA CAVA SEMI LUNAR VALVE LEFT ATRIUM RIGHT ATRIUM LEFT VENTRICLE ATRIOVENTRICULAR VALVES RIGHT VENTRICLE

Valves in the heart prevent the backflow of blood

The internal structure of the heart © Pearson Education Ltd 2008 This document may have been altered from the original

Structure of the Heart

Why is a mammalian heart is divided into a right and left side? Keeps oxygenated and deoxygenated blood separate Allows as much oxygen as possible to be carried to the tissues Allows different pressures to exist – left more pressure required to force blood to body whereas right side requires less as forcing blood a shorter distance to lungs

Main adaptations of the heart Composed of cardiac muscle A specialised tissue that can contract automatically, powerfully and without fatigue. All cells in cardiac muscle are connected by specialised junctions called intercalated discs. This allows the rapid spread of impulses through the muscle ensuring that all cells contract at the same time

Main adaptations of the heart Thickness of the walls The thickness of the walls in the different heart chambers reflects their function. Atria: thin muscle as only pumps blood a short distance Right Ventricle: thicker muscle than atria – forcing blood a further distance to lungs. Left Ventricle: thickest walls – has to force blood all the way round body

Main adaptations of the heart Valves Ensure unidirectional flow through the heart and prevent backflow. The AV valves Location: between atria and ventricle Function: to prevent blood flowing back into atria when ventricles contract The Semilunar valves Location: found at the openings of the aorta and pulmonary artery Function: prevent backflow of blood into ventricles during diastole

Valve structures

The cardiac cycle © Pearson Education Ltd 2008 This document may have been altered from the original

Semi-lunar valves open Atrial Systole AV valves open semi-lunar valves closed AV valves close Filling of ventricles atrial systole Ventricle muscles contract Pressure increases Ventricular Systole Ventricular Diastole Semi-lunar valves close Ventricles relax Semi-lunar valves open Blood enters arteries Pressure in the ventricles falls AV valves open

Action of the atrioventricular valves © Pearson Education Ltd 2008 This document may have been altered from the original

Describe the sequence of events involved in one heart beat atrial systole / atria contract ; blood passes into ventricles ; atrioventricular / AV valves open ; ventricular systole / ventricles contract ; blood to, the arteries /Aorta and Pulmonary Artery; via open, semilunar valves ; Atrioventricular (AV) valves shut to stop backflow ; relaxation / diastole, of ventricles (and atria) ; semilunar, valves shut to stop backflow ;

Pressures changes in the aorta, left ventricle and left atrium during one heartbeat © Pearson Education Ltd 2008 This document may have been altered from the original

Week 8 Describe how heart action is coordinated with reference to the sinoatrial node, the atrioventricular node and the Purkyne tissue. Interpret and explain electrocardiogram (ECG) traces with reference to normal and abnormal heart activity. © Pearson Education Ltd 2008 This document may have been altered from the original

The pathway followed by the wave of excitation © Pearson Education Ltd 2008 This document may have been altered from the original

A normal ECG trace compared with others indicating an unhealthy heart Week 8 A normal ECG trace compared with others indicating an unhealthy heart © Pearson Education Ltd 2008 This document may have been altered from the original