Heildaræðaviðnám

Heildaræðaviðnám, often translated as total peripheral resistance or systemic vascular resistance, is a physiological concept in the circulatory system. It represents the overall resistance to blood flow in the systemic circulation. This resistance is primarily determined by the diameter of the blood vessels, their length, and the viscosity of the blood.

The concept is crucial for understanding blood pressure regulation. Blood pressure is the force exerted by circulating blood on the walls of blood vessels. It is influenced by two main factors: cardiac output (the amount of blood pumped by the heart per minute) and heildaræðaviðnám. The relationship can be simplified by the formula: Mean Arterial Pressure = Cardiac Output × Heildaræðaviðnám.

When heildaræðaviðnám increases, meaning the blood vessels constrict or narrow, the heart has to work harder to pump blood through them, leading to higher blood pressure. Conversely, when heildaræðaviðnám decreases, as in vasodilation where blood vessels widen, blood flows more easily, and blood pressure tends to fall.

Factors that can influence heildaræðaviðnám include hormones like adrenaline and angiotensin II, which cause vasoconstriction, and certain medications. Conditions like atherosclerosis, where arteries become narrowed and hardened, significantly increase heildaræðaviðnám. Understanding and measuring this parameter is vital in diagnosing and managing cardiovascular diseases.