The Study Of Nonlinear Dynamic Behaviors In Sinoatrial Node Cells

As environment pollution is becoming more and more serious,and with the trend of aging acceleration and as well as other reasons,heart disease has become one of the major threats to human health.Researchers have found that the rate of sudden cardiac death in our country has been at the forefront of the world,and more serious is that the incidence of heart disease gradually become younger and younger.Therefore,it is an important research topic to research deeply the external factors and the mechanism of abnormal fluctuations in the heart and it is an important research topic in the current scientific research and clinical medicine.Sinoatrial node(SAN)plays a key role in our heart activities,its internal structure is very complex and it has an important influence on the heart’s rhythm.It is reported that,not only the open or close probability of the ion channels on the myocardial cell membrane are different,so,this may affect the rhythm of the heart,but also,the disturbance from the outside environment may influence person’s emotions and feelings,thus the nervous system secretion in human body may be affected,finally this will change the rhythm of the heart.From the experiment,it is found that induced by the external stimulation,the acetylcholine secreted by vagus nerve will decelerate the heart rhythm and even make a 50% reduction.Compared to an adult heart,old heart’s myocardial cell death rate is increased.This may weakthe heart’s pacemaker function continuously.Simulation results show that there are a lot of reasons for causing the cardiac conduction disorders,such as,the increment of dead cells,the reduction of sodium current,sodium channel gene(SCN5A)mutation,and so on.These factors may become worse with aging,even in severe cases,the pacing activities and signal conduction will be blocked.Above results show that the SAN cell activity reduce,largely linked with its aging.On the other hand,if proper external noise or signal stimulation is introduced,the abnormal pacemaking could be reduced,or may even be recovered to the normal level.Thus,it is a very meaningful,and very necessary research work,to study the regulation of the cardiac pacemaker activity,by adding some appropriate external noise or signal to stimulate the SAN.In the first part of the dissertation,we introduce some basic knowledge and background information,such as the heart and the sinus node’s construction,cell ion channels and abnormal heart rhythms and so on.In the second part,we introduce the model that we used in this paper.In the third part,we select SAN cell model as the research object,and study the effects both of aging factors and external different stimuli regulation on the pacemaking behavior and its beating mechanism.With increment of the degree of cardiac aging,the number of death cell and decrease in the sodium current in cells,these factors may result in a decrease in the activity of myocardial cells,thereby the SAN pacemaker function will reduce,and in the serious cases the heart death even appear.Now,if we introduce an external low-frequency signal,the abnormalsituation could be reduced or eliminated.In the fourth part of the dissertation,based on the previous research work,it is found that the effects of the noise on the pacemaking of SAN could be obtained by introducing the environmental noise.In summary,by using computer simulation,we have theoretically researched the pacemaking behavior of SAN and our results show that the pacing are closely linked with signal transfer behavior.It will help us to reveal the internal mechanism of the complex heart system,and to provide a theoretical basis to the heart disease treatment.It also provides scientific basis for the further experimental and clinical diagnosis of abnormal pacemaking behavior of SAN.