intro to heart & cardiac conduction system

function of the heart

to pump blood and keep it moving though the blood vessels

3 types of circulations in the body

* pulmonary circulation
* systemic circulation
* coronary circulation

pulmonary circulation

circulating blood between the heart and lungs

systemic circulation

circulating blood between the rest of the body and the heart

coronary circulation

circulating blood in the heart

3 layers of the heart

* epicardium
* myocardium
* endocardium

epicardium

outermost layer of the heart formed from the visceral pericardium lining the heart

myocardium

middle muscular wall of the heart composed of cardiac muscle tissue

endocardium

inner layer of the heart made up of simple squamous epithelium

chordae tendineae

hold the tricuspid/bicuspid valves closed during ventricular systole

automaticity

ability to depolarize spontaneously and trigger an action potential in the absence of nervous or hormonal stimulation

SA node

has pacemaker cells that depolarize and send an action potential through the myocardium from the SA node to the AV node

pathway of action potential from SA node to AV node

travel across the wall of the atrium

why is the action potential delayed through the AV node

gives atria time to finish their contraction

AV bundle and L&R bundle branches

conduction fibers the action potential travels through as it spreads down the interventricular septum of the heart towards the apex

direction of action potential spread through ventricles

upwards

purkinje fibers

fibers found in the wall of the ventricles

ECG

graphical recording of the electrical activity of the heart

P wave

spread of action potential from SA node to AV node

* results in atrial systole

QRS complex

spread of action potential through purkinje fibers

* results in ventricular systole

T wave

spread of repolarization through ventricles

* results in ventricular diastole