Coordination of Cardiac Cycle www assignmentpoint com 03
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Co-ordination of Cardiac Cycle www. assignmentpoint. com
03 January 2022 Co-ordination of the Cardiac Cycle Aims • Describe how heart action is coordinated with reference to the sinoatrial node (SAN), the atrioventricular node (AVN) and the Purkyne tissue • Be able to interpret and explain electrocardiogram (ECG) traces, with reference to normal and abnormal heart activity www. assignmentpoint. com
• The heart is made of cardiac muscle. • When the cells receive an electrical impulse they contract - causing a heartbeat. • Cardiac muscle is myogenic - it can contract on its own, without needing nerve impulses. www. assignmentpoint. com
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Sinoatrial node (SA node) • This specialized node is found on the upper inside wall of the right atrium. • The SA node is known as the pacemaker of the heart and initiates a heartbeat every 0. 85 seconds. • This signal travels across the atria causing them to contract and load the ventricles with blood. • Ventricles are electrically insulated from atria so they don’t contract yet. www. assignmentpoint. com
Atrio-ventricular node (AV node) • The AV node is located on the bottom surface of the right atria and is responsible for initiating the contraction of the ventricles. • Electrical impulse passes to ventricles via AV node and the Bundle of His. They pass the impulse to the base of the ventricles (~ 0. 1 s delay). • The bundle of His is a group of fibres that conduct impulses to Purkyne fibres which carry impulses to left & right ventricles. • Ventricles then contract from the bottom upwards. www. assignmentpoint. com
No impulse • Cardiac muscle relaxes = diastole www. assignmentpoint. com
Electrocardiograph P = atrial systole QRS = ventricular systole T = ventricular diastole www. assignmentpoint. com
• Records electrical activity of heart to monitor heart function. • Pacemaker generates electrical currents in body fluids around the heart - detected by electrodes to produce ECG • Heart muscle: depolarises (loses electrical charge) when it contracts repolarises (regains charge) when it relaxes www. assignmentpoint. com
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Ventricular fibrillation is an abnormal heart rhythm that is disorganized and irregular. www. assignmentpoint. com
Ventricular tachycardia is a rapid, regular heart rhythm that originates in the lower chambers of the heart. www. assignmentpoint. com
Heart block refers to a delay in the normal flow of electrical impulses that cause the heart to beat. www. assignmentpoint. com