The Cardiac Cycle Flashcards
What term describes the control of the heart?
Myogenic, whereby stimulation arises from within heart itself and leads to depolarisation. No stimulation from CNS
What is the role of the SAN?
It is located in the right atrium and it acts as heart’s pacemaker. Causes depolarisation of atria and leads to them contracting. This initiates heartbeat.
What is the role of the Annulus Fibrosus?
Is a region of non-conducting tissue between the atria and the ventricles. It prevents depolarisation spreading to the ventricles directly.
What is the role of the AVN?
Wave of excitation reaches the AVN. There is a slight delay here. It then passes the wave of depolarisation into the bundle of His.
What is the bundle of His?
This is a group of conducting fibres in the septum of the heart. This splits into 2 branches and carries the wave of excitation into the Purkyne tissue.
Describe role of Purkyne tissue?
Consists of conducting fibres that penetrate through septum and spreads around ventricles. It spreads the depolarisation from the apex of the heart.
What happens during atrial systole?
.Impulse from SAN .Atrial pressure greater than ventricular pressure .Atria contract .Atrioventricular valves forced open .Blood flows into the ventricles .Semilunar valves are closes
What happens during ventricular systole?
.Ventricular pressure greater than arterial pressure .Ventricle walls contracts .Blood pumped into arteries .Semi-lunar valves are open .Atrioventricular valves are closed .Atrial walls relaxed
What happens during diastole?
.Ventricles relax
.Atria relax
.Atria fill with blood
.Arterial pressure is greater than the ventricular pressure
.Semi-lunar valves are closed
.Atrioventricular valves are closed initially but rising pressure in atria causes atrioventricular valves to open
.This causes the ventricles to fill a bit
