PATHOPHYSIOLOGY Dr. Wasfi Dhahir Abid Ali Department of medical sciences –College of Nursing – University of Basrah
Blood pressure • Blood pressure (BP) define as the pressure of circulating blood on the walls of blood vessels • Blood pressure is one of the vital signs, along with respiratory rate, heart rate , oxygen saturation and body temperature. • Normal resting blood pressure in an adult is approximately 120 millimeters of mercury systolic, and 80 millimeters of mercury diastolic, abbreviated "120/80 mm. Hg.
hypotension& Hypertension • Blood pressure that is low due to disease state is called hypotension, and pressure that is consistently high is hypertension. • Both have many causes. and may be of sudden onset or of long duration. Long-term hypertension is a risk factor for many diseases, including heart disease , strok and kidney failure. • Long-term hypertension is more common than long term hypotension and often goes undetected because of infrequent monitoring and the absence of symptoms.
Mean arterial pressure The mean arterial pressure (MAP) is the average over a cardiac cycle and is determined by the cardiac output (CO , systemic vascular resistance SVR)and central venous pressure(SVR) MAP = P Diastole + 1 ( P systole - P diastole ) 3
Mean systemic pressure Or mean circulatory filling pressure, (MCFP)) is defined as the mean pressure that exists in the circulatory system when the blood has had a chance to redistribute evenly to all vessels and organs. MSP is approximately 7 mm of Hg. It is an indicator of how full the circulatory system is (i. e. the volume of blood in the system compared to the capacity of the system), and is influenced by the volume of circulating blood and the smooth muscle tone in the walls of the venous system (which determines the capacity of the system
Regulation of blood pressure • The endogenous regulation of arterial pressure Baroreceptor reflex : In the high pressure receptors zones detect changes in arterial pressure. These baroreceptors send signals ultimately to the medulla of brain stem , baroreceptors are located in the left and right carttid sinuses and in the aortic arch Renin- angiotensin system (RAS): This system is generally known for its long-term adjustment of arterial pressure. This system allows the kidney to compensate for loss in blood volume or drops in arterial pressure by activating an endogenous vasoconstrictor known as angiotensin II.
Regulation of blood pressure Aldosterone release: This steroid hormone released from the adrenal gland cortex in response to angiotensin II or high potassium levels. Aldosterone stimulates sodium retention and potassium excretion by the kidneys. Since sodium is the main ion that determines the amount of fluid in the blood vessels by osmosis, aldosterone will increase fluid retention, and indirectly, arterial pressure. Baroreceptor in low pressure receptor (mainly in the venae cavae and the pulmonary veins , and in the atria ) result in feedback by regulating the secretion of antidiuretic hormone (ADH/Vasopressin), renin and aldosterone . The resultant increase in blood volume results in an increased cardiac output in turn increasing arterial blood pressure. •