Introduction
The cardiovascular system consists of the heart and the vascular tree which distributes the blood to the tissues of the body. Although the heart is somewhat independent and free running, it has neural connections that can accelerate or depress its activity. Applied EMFs could influence heart function by changing peripheral vascular resistance, by a direct action on the electrical system of the heart muscle, or by a secondary effect via the CNS. The blood is a fluid that contains a variety of cellular elements including the red and white blood cells. Red cells carry dissolved oxygen, picked up in the lungs, to the body's other tissues; the white cells, in addition to protecting against invading microorganisms and foreign proteins, are intimately involved in local inflammation and tissue-repair processes. Both cell types are produced in the hematopoietic tissues (located primarily in the bone marrow), and they have a finite lifetime in the circulation before being replaced by new cells. The fluid portion of the blood is a mixture of many chemicals with diverse metabolic functions-chemical transport, blood clotting, and immune response are three examples.
Feedback systems that are only partially understood regulate both the cellular and non-cellular composition of blood. For example, when an organism suffers a hemorrhage or an infection, the hematopoietic tissues are mobilized to produce the required types of cells in the required numbers. As we have seen in other areas, an EMF impact on the blood could arise from a primary effect on the tissue itself, or from a secondary effect, with the field affecting the systems that regulate blood composition.