问题 问答题

简述心室肌动作电位与心电图波形不同的原因。

答案

参考答案:由图1和图2可见心室肌细胞动作电位波形与心电图波形都是来自于心肌细胞兴奋产生的电活动,但二者的图形确实完全不同。



心室肌细胞的动作电位波形反映了单个细胞的电变化。即心室肌细胞的静息电位由K+平衡电位决定,动作电位包括Na+内流引起的0期去极化,K+外流、Ca2+内流等引起的1期、2期和3期复极化,3期复极末由于Na+-K+泵和Ca2+泵的作用,膜电位在4期时又回到了静息期。
心电图是反映在一个心动周期中,由窦房结产生的兴奋,依次传向心房和心室,这种兴奋的产生和传布所伴随的生物电变化,通过周围组织传到全身,使身体各部位在每一心动周期中都发生有规律的大小和方向不同的电变化,用引导电极置于肢体或躯体的一定部位记录出来心电的P波、QRS波群和T波等变化波形。

解析: 心肌细胞动作电位的波形;
心电图的波形;
心肌细胞动作电位与心电图之间的关系;
为何心肌细胞动作电位与心电图波形完全不同。
只有搞清心室肌细胞的动作电位和心电图的产生原因和它们之间的关系,才能对波形完全不同给予合理的解释。

单项选择题 B型题
单项选择题


阅读下面这篇短文,短文后列出7个句子,请根据短文的内容对每个句子做出判断。

Smoking
Since 1939, numerous studies have been conducted to determine whether smoking is a health hazard. The trend of the evidence has been consistent and indicates that there is a serious health risk. Research teams have conducted studies that show beyond all reasonable doubt that tobacco smoking is associated with a shortened life expectancy.
Cigarette smoking is believed by most research workers, in this field to be an important factor in the development of cancer of the lungs and cancer of the throat and is believed to be related to cancer of some other organs of the body. Male cigarette smokers have a higher death rate from heart disease than non-smoking males. Female smokers are thought to be less affected because they do not breathe in the smoke so deeply.
Apart from statistics, it might be helpful to look at what smoking tobacco does to the human body. Smoke is a mixture of gases, vaporized chemicals, minute particles of ash and other solids. There is also nicotine, which is powerful poison, and black tar. As smoke is breathed in, all those components form deposits on the membranes of the lungs. One point of concentration is where the air tube and bronchus divides. Most lung cancer begins at this point.
Filters and low tar tobacco are claimed to make smoking to some extent safer, but they can only slighfiy reduce, not eliminate the hazards.

Smoking may induce lung cancer.

A.

A. Right

B.

B. Wrong

C.

C. Not mentioned