Electric Properties of Cardiac Muscles: Action Potentials and Conductive Tissue, Study Guides, Projects, Research of Cardiology

Download Electric Properties of Cardiac Muscles: Action Potentials and Conductive Tissue and more Study Guides, Projects, Research Cardiology in PDF only on Docsity! Electric properties of cardiac muscles Myocardium has got 2 types of cells  Contractile tissue ( muscles )  Non- Contractile tissue (auto-rhythmic cells) or conductive tissue. The Contractile muscles are: 1. Ventricles 2. Atria Non- Contractile tissue (conductive tissue): 1. SA Node 2. AV Node 3. Bundle of His 4. Bundle of branches 5. Purkinje fibers They are responsible for rhythmicity (Independent of nerve supply) Action potential means depolarization followed by repolarization The shape of action potential in all nerves is spike-shape but cardiac muscles have got different shape from different parts of heart. Duration of action potential is from 200 - 250 ms (ventricles) Cardiac muscle has the longest duration of action potential in purkinje fibers. Both similar graph shape Ventricle action potential Duration: 250 milliseconds Atrium action potential Duration: 100 milliseconds All conductive tissue (non-contractile) have prepotential period (slow depolarization period). Purkinje fibers has similar graph to the Ventricle (Not atrium) except 2 things which are: 1. Duration of action potential (longer in Purkinje fibers- up to 400 ms). 2. Prepotential period. Have 5 phases: Phase 0: depolarization due to rapid entering of Na+ ions through fast sodium channels till reach to +30 mv which is the peak of depolarization Phase 1: early repolarization phase because of transit outflux of K+ ions (it is very short phase and for very short time too) Phase 2: called plateau phase (flat phase) because of Ca++ entry to the cell (there is No potassium entering) Phase 3: outflux of K+ ions the cell (K+ out) This graph indicates SA, AV nodes action potential Ventricle and Atrium action potential