Week 3 - Cardiac System

The hearts natural pacemaker, that controls the heart rate. The SA node consists of a cluster of cells that are situated in the hearts right atrium

• generates an electrical impulse that causes the atria to contract • it has automatically, meaning it initiates the electrical conduction of the conduction system independently

The next stage of conduction pathway after SA; located in the Koch triangle near the coronary sinus on the inter-arterial septum - electrically connects the the right atrium and the right ventricle

Slows the conduction rate to allow for complete contraction of both atria • can initiate a beat if the SA node fails to ‘fire’

The next stage of conduction pathway after SA and AV; located between the atria and ventricles in the interventricular septum

After the electrical impulse is sent from the SA node to the AV node, the bundle of his quickly conducts the impulse through the interventricular septum to the tip of the ventricles

Two branches of the AV bundle; located in the interventricular septum

Relays electrical conduction into the right and left ventricles towards the apex of the heart

Any specialised cardiac muscle fibres forming a network in the ventricular walls that conduct electric impulses responsible for the contractions of the ventricles

They conduct the impulse to the ventricles creating synchronised contractions of the ventricles, causing ventricular systole, pumping blood out of the aorta and around the body

• a quick, pain free easy diagnostic investigation to look at the hearts electrical activity

Noises generated by the closing of paired valves during the beating of the heart; auscultated at the apex of the heart using a stethoscope

First ‘lub’ indicates the simultaneous closure of the AV valves (bicuspid and tricuspid) during ventricular systole

The ‘dub’ sound indicates the simultaneous closure of the SL valves (aortic and pulmonic) during ventricular diastole

• Pericardium • Myocardium • Endocardium

• Fibrous Pericardium - Serous Pericardium

Lubricates the heart and prevents friction

• Visceral Serous - Parietal Serous

• covers myocardium - inner most layer of the pericardium

Parietal serous

Cardiac muscle tissue arranged in intercalated discs that contracts and relaxed to force blood through the heart to the body • the middle, muscular layer

• Thin, Shiny membrane that lines the valves and is continuous with the large blood vessels • minimises friction to blood flow preventing coagulation of blood • Inner layer

Outer layer of the heart wall

The part of the circulatory system which carries deoxygenated blood from the right ventricle to the lungs and returns oxygenated blood to the left atrium and ventricle