Pre-lecture reading CVSL4 – Electrical basis
The function of the heart is critically dependent on electrical activity. Spontaneous and rhythmic electrical activity govern muscle contractions. This lecture discusses the generation and transmission of electrical activity in the heart. Spontaneous electrical activity normally begins in the SA node which then spreads through the entire specialised conductive system of the heart to the Purkinje fibers which directly excites cardiac muscle to effect contraction. The generation of the SA node signal is controlled by, though not dependent on, the autonomic nervous system.
- The cardiovascular (CVS) system comprises the heart, arteries, veins and lymphatics.
- The main function of the CVS is to service the needs of the tissues.
- The heart comprises 2 pumps in series.
- The left heart must pump with adequate pressure and flow to service the tissues.
- Both pressure and flow are further regulated by vascular system (especially the arterioles) so that optimal perfusion pressure and flow occur at the capillaries.
- Proper function of the heart depends on a coordinated, intricate electrical network.
- Examples of uncoordinated electrical activity include ventricular fibrillation, atrial fibrillation and heart blocks.