生理 循环（Physiological cycle）.docVIP

生理 循环（Physiological cycle） 1. briefly describe the mechanism of action potential of ventricular myocytes. The depolarization and repolarization process of ventricular action potential can be divided into 5 periods: 0. Depolarization process. The formation mechanism is due to the rapid influx of Na +. Repolarization 1: the transient outward ionic current caused by K+. The 2 stage: from repolarization outward ionic Ca2 + inward current and load carrying flow induced by K+. Repolarization 3 phase: K+ outward ion current is further strengthened. Phase 4: also known as the resting phase, the active transport of ions in this phase of the membrane enhanced, excreted Na + and Ca2 +, back to K +, restored the ion distribution inside and outside the membrane to the resting state. 2. what are the physiological characteristics of cardiomyocytes? The physiological characteristics of cardiomyocytes include automaticity, conductivity, excitability and contractility. Among them, the automaticity, conduction and excitability belong to the electrophysiological characteristics of myocardial cells. Contractility is a mechanical property. 3. the atrio ventricular delay and its physiological significance. Atrioventricular junction conduction slow, excited by the atrioventricular junction when the delay time is longer, called atrio ventricular delay. The physiological sense is that the atria and ventricles do not become excited at the same time, thus ensuring the sequential activity of the atria and ventricles and the time at which the ventricles have enough blood to fill. 4. what periods of cardiac cycle changes does it include? The changes of myocardial excitability cycle include effective refractory period, relative refractory period and supernormal phase. The effective refractory period includes absolute refractory period and local reaction period. 5.. What are the normal pacemaker sites and potential pacemaker sites? The sinus node automaticity is highest, impulse propagation accordi