If you are worried about your blood pressure reading, remember this: blood pressure is never constant; it is a condition that changes according to the needs and requirements of the body, and it does so frequently in the course of every day. Whether it goes up or down depends on a wide variety of different factors.

The lowest pressure readings normally occur while sleeping. During the day with its physical and psychological demands and strains, pressure usually goes up, adjusting constantly to different requirements and muscle activities. Let us take two examples:

When we stand erect, the blood, because of its weight, flows down to the lower extremities. At the same time, the blood pressure goes down and could continue to do so to the point of danger if the regulatory mechanism of our circulation would not automatically raise the pressure and maintain it at a normal level by constricting the peripheral arteries. If this mechanism works too slowly or not satisfactorily it can cause a temporary blood shortage in the brain. The result is a feeling of light-headedness and dizziness. Most of us have at one time or another arteries constrict, with the exception of the vessels of the legs, which dilate. Your blood pressure goes up and the blood flow to your legs increases. Once you have reached the top and rest, the blood requirements of your leg muscles return to normal, and with it the heart activity and blood pressure.

We know from experience how excitement can affect circulation: "pounding heartbeats", accompanied by a definite increase in blood pressure. That holds true regardless of the cause, whether pleasure or pain, shame or fear, or simple irritation over being caught in a traffic jam when you're in a hurry or feel pressured on your job. This rise in blood pressure under conditions of psychological stress or nervous tension helps you to keep under control in critical situations by making you more alert and responsive. When the specific cause of the excitement is removed or comes to an end, the blood pressure returns to its baseline level.

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