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心脏的大小仅同于自己的拳头,可它却是人体最辛苦、最重要的器官。当它还在娘胎里、胚胎形成刚3个月时,就开始日以继夜地有规律地工作了。它每分每秒都不停地收缩和舒张,永不停止,如若停止了,也就意味着整个生命结束了。 心脏之所以能够如此有规律有节奏地收缩、舒张,除了受大脑以及神经体液的调节之外,主要是它自备一个独特的、能指挥心脏搏动的系统,称为心脏传导系统,包括窦房结、房室结、房室束和蒲氏纤维。正常情况下,心脏的每一次搏动,首先由窦房结(内含数以万计的起搏细胞)产生兴奋,并经整个传导系统迅速传递到心肌细胞,使心房肌或心室肌发生同步收缩和舒张,即一次正常的心跳。若以每分钟心跳70次计算,一年的心跳将高达4千万次;若以每次搏动左心室射入主动脉的血量约为70毫升计算,
The size of the heart only with their own fist, but it is the body’s most difficult, the most important organ. When it was still in the womb, embryos formed just three months, began to work regularly around the clock. It keeps shrinking and relaxing every second, and never stops. If it stops, it means the whole life is over. In addition to being regulated by the brain and neurohumoral fluid, the heart is able to regulate and rhythmically contract and relax so regularly, mainly because it has its own unique system that can direct the heart beat, called the heart conduction system, including the sino-atrium Knot, atrioventricular node, atrioventricular bundle and Puffer fibers. Under normal circumstances, every heart beat, the first of the sinus node (including tens of thousands of pacemaker cells) generated excitement, and the entire conduction system quickly passed to the cardiomyocytes, so that atrial or ventricular systolic contraction And diastolic, that is, a normal heartbeat. If 70 beats per minute calculation, the heart rate will reach 40 million times a year; if the left ventricle per beat into the aorta blood volume of about 70 ml calculation,