Human heart function is continuous individual parts of the body to reflux of blood pumped into the veins, transported to various parts of the body. To do this job, you have to stop cardiac contraction and relaxation. Contraction in order to pump out blood and relax to allow blood into the heart. These actions have to rely on all cardiac myocytes coordinated activities. To shrink fully retracted, to relax all relax. Now that should be coordinated, the two elements can not be missing: First, the unified command center, the second is smooth information transfer. This nervous system is very similar, but the heart, there are no specific nerves responsible for this matter. Dispatch and transmission of information are made of special cardiomyocytes responsible. These cells and other normal cardiomyocytes very different, although it is also called cardiomyocytes, but basically there is no ability to contract the muscle cells.
At the top of this dictator conduction system is a group of P cells, they are responsible for calling the shots, other non-contractile cells form a network of vertices P cells within the heart. P cells orders are highly disciplined, you can not rely on any external instruction. Skeletal muscle contraction can not cut off the nerves, but the heart is completely cut off from the body, it can still beat your own time, it is because of this self-discipline. Normal heart, what is the frequency of P cells, the whole heart is what frequency, such as P cytokinin 60 times per minute, that our heart rate is 60 beats per minute. Because P gathering place called the sinus node cells, so called normal sinus rhythm.
Virtually all cardiac myocytes have self-discipline, will separate out a contraction of myocardial cells, it can also just keep shrinking, why should listen to P cells dictatorship it? Is generally considered the highest rhythm P cells, the lower the downstream rhythm, rhythm only follow the rhythm of the low high activity. Like a pendulum, each has its own fixed pendulum swing cycle, but if you catch it hard to quickly swing the pendulum swing naturally fast. If for some reason, conduction is interrupted upstream and downstream will be autonomy within a very short time. For example, the normal sequence of atrial systolic contraction of the first, the blood into the ventricle, and ventricular contraction again, pump the blood out of weeks. Atrial and ventricular contraction frequency matching, if information between atrial and ventricular conduction path is broken, then the atrium and ventricle will jump their own, no matter who is who.
Although heart jump or not to jump in the high degree of autonomy under the dictatorship P cells, but also had to suffer the whole body control, sometimes you have to adjust our overall operating frequency. For example, people in the excitement when the blood will release large amounts of catecholamines, bind to catecholamine receptors will cause P cells faster signals, to the night, the vagus nerve dominant, acetylcholine dominant, binds to the acetylcholine receptor, the It can cause the heart to slow down. Pesticide poisoning people because blood acetylcholine decomposition enzyme is organophosphorus tripping, so large accumulation of acetylcholine, heart rate will become slower until it stops beating. Heart rate also affected by many other factors, these effects are applied to the heart by the autonomic nervous system, people will not be affected by the disposal. Although it was claimed by the idea to make her heart to speed up or slow down, unless it is forced to think of himself got angry, have generally been unsuccessful. If that's the idea of control, not as good as it laps around the playground.
(Author: lw56102)
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