Most people hardly think about getting up. They simply get up, day after day, dozens or hundreds of times.
Yet what our circulatory system has to do is impressive. 85% of the blood is always in the veins. When we stand up, another 10% or half a liter is added within seconds. It "sinks" into the veins of the legs and abdomen. If no countermeasures were taken here, the blood pressure would immediately drop by 50 mmHg. Instead of 120 mmHg systolic (the upper value) only 70 mmHg. This is no longer sufficient for cerebral perfusion.
So countermeasures are urgently needed. When the pressure receptors or also Bart receptors in the carotid artery or the carotid artery signal a drop in pressure, threefold countermeasures are taken:
- Heart rate and the ejection output of the heart increase.
- The veins contract and ensure an increased return flow of blood to the right heart.
- Arteries contract to make the heart work against more resistance. The pressure thus increases.
This regulation work is called orthostasis reaction (orthostasis = standing upright) and is in everyday life one of the performances that the cardiovascular regulation most often demands and also constantly trains through the frequent change of standing up/sitting/lying down.
The whole runs with the healthy one within seconds fully automatically. Particularly sporty active people do not spend any thought on it. But if you have been lying in bed for a few days and then suddenly get up, you already feel a certain "deconditioning". The circulation must first adapt again.
Likewise, many medications/drugs have an influence on the circulation. If you've had too much to drink, you'll feel dizzy when you get up from a round of wine: your circulatory system has already been affected by the alcohol.
In a large number of people, the regulation of the circulatory system is frequently or permanently disturbed, and in some there is a real condition that can severely impair the quality of life. Some patients only get slightly dizzy or have a little heart palpitations, then it's all over again. But there may also be severe symptoms: visual disturbances, sweating, shortness of breath, rapid heartbeat and anxiety, even blackness before the eyes and unconsciousness, the affected person falls down.