Circulatory system Flashcards
What is the structure of the SA node?
small mass of specialised cells.
What is the cardiac cycle?
Sequence of events taking place within a single complete heart beat
Functions of the SA node
It is the source of the stimulus for the contraction of the heart. initiates heart beat and sets heart rhythm, therefore called the pacemaker.
Location and structure of the AV node
Small mass of specialised cells. Located between the wall separating the left and right atrium.
Formation of AV bundle, bundle branches and Purkinje fibres.
AV bundle arises from the AV node, passes through fibrous rings separating atria from ventricles at the upper end of the ventricular septum, divides into left and right bundle branches. Within the ventricular myocardium, branches to form a network of fine fibres called purkinje fibres.
Electrical impulses generated by the SA node.
Entry of blood into the right atrium from the SVC stimulates the SA node to generate electrical impulses, sweeps across the myocardium of 2 atria, causing a wave of contractions.
Electrical impulses generated by the AV node.
The electrical impulses generated by SA node reach the AV node, stimulates it to produce own impulses, transmitted to AV bundle , bundle branches and purkinje fibres, causing a wave of contractions that sweep upwards from the apex of the heart across the walls of ventricles.
Why is blood clotting important? And what happens to the blood when tissue damage occurs?
When tissue damage occurs, blood flows out and coagulates to form a blood clot , which prevents further blood loss and entry of pathogens, which is of clear survival value.
