Pulmonary hypertension is a rare lung disorder in which the arteries that carry blood from the heart to the lungs become narrowed, making it difficult for blood to flow through the vessels. As a result, the blood pressure in these arteries -- called pulmonary arteries -- rises far above normal levels.
Homeostatic Control Mechanisms Homeostatic Control Mechanisms are devices for maintaining or restoring homeostasis. They involve virtually all of the bodyâs organs and systems.
Two general mechanisms are involved in homeostatic regulation: autoregulation and extrinsic regulation: 1  Autoregulation, or intrinsic regulation, occurs when the activities of a cell, tissue, organ, or organ system adjust automatically in response to some environmental change. For example, when oxygen levels decline in a tissue, the cells release chemicals that dilate local blood vessels.