The heart conduction system

Lloyd Dean

The Heart

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Left Atrium

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Left Ventricle

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Tricuspid Valve

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Pulmonary Valves

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Right Atrium

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Right Ventricle

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PulmonaryVeins

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Pulmonary Artery

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Click on the Aorta

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Vena Cava

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Cardiac OutputWhat is it?

The amount, or volume, of blood pumped by the heart per minute (mL blood/min)

Heart rate and Stroke Volume make this up

Heart rate (HR) – beats per minute

Stroke Volume (SV) – Millilitres (mL) of blood pumped out with each beat.

Cardiac Output = HR x SV

An average person has a resting heart rate of 70 beats a minute and a resting stroke volume of 70mL/beat

Work out their cardiac output

CO = HR x SV CO = 70 x 70CO = 4900 mL/minute

Conduction SystemThe hearts atria, and then ventricles, need to contract

simultaneously

Conduction system includes several components;

Sinoatrial (SA) node – Found in the myocardium at the top of right atrium

SA node is commonly know as the heart’s pacemaker

Each electrical impulse travels through the muscle fibres of the atria and ventricles, causing them to contract

Atrioventricular (AV) node delays the electrical impulse to allow the atria to contract and empty all blood

AV node is an electrical relay station that sends an impulse through the ventricles along special fibres called “His-Purkinje” fibres.