the cadiac conduction system - 1

what is the caridac conduction system

a group of specialised cells located in the wall of the heart which send electrical impulses to the cardiac muscle causing it to contract

myogenic

the heart can generate its own impulses

Sinoatrial node - SAN

found in the right atrium that generates heartbeat

atrioventricular node - AVN

the node relays impulses from the upper and lower sections of the heart

systole

when the heart contract

bundle of his

transmit electrical impulses from AVN via bundle branches to ventricles

purkinje fibres

muscle fibres that conduct impulses in the walls of the ventricles

cardiac conduction system 6 main points

SAN

Atrial systole

AVN

Bundle of his

Bundle branches

Purkinje fibres

Ventricular systole

what is diastole

• passive filling phase - 0.5s

• increase pressure of blood against valves - blood to ventricles

• past tri and bi

• volume of blood after filling - end diastollic volume

what is atrial systole

• contraction of both atria

• increase pressure in atria → forces blood to ventricles

• semi lunar valves close

what is ventricular systole

• both ventricles contract

• increase pressure → blood out ventricles

• tri and bi stay shut

• semi lunar valves close after - to prevent back flow

• lasts 0.3s at rest

step 1 of the conduction cycle:

• start at SAN

• thorugh atria walls

• causes atrial systole → blood through tri and bi

step 2 of the conduction cycle:

• impulse at AVN

• AVN delays by 0.1s to allow atria to finish contracting

• relays to bundle of his

step 3 of the conduction cycle:

• impulse down bundle of his

• located in septum

• splits into 2 - bundle branches

• impulse to both ventricles

step 4 of the conduction cycle:

• impulse to purkinje fibres

• spread throughout ventricles

• spread through ventricle walls

• heart relaxes and fills