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Chapter 33 Hypertension

Chapter 33 Hypertension. Amazing Fact.

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Chapter 33 Hypertension

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  1. Chapter 33Hypertension

  2. Amazing Fact According to the American Heart Association (2007) one in three U.S. adults has high blood pressure, but because there are no symptoms, nearly one-third of these people don't know they have it. In fact, many people have high blood pressure for years without knowing it. Uncontrolled high blood pressure can lead to stroke, heart attack, heart failure or kidney failure. This is the reason why high blood pressure is often called the "silent killer."

  3. Blood Pressure • In a healthy adult blood pressure is about 120/80 mmHg. Systolic pressure refers to the level of blood pressure while the heart is contracting and is represented by the top number (120 mmHg). Diastolic pressure, the level of blood pressure in between heart contractions, is represented by the bottom number.

  4. Factors Contributing To Blood Pressure • blood pressure is determined directly by two factors, cardiac output, the volume of blood pumped by the heart each minute, and the resistance to blood flow in the vessels, primarily the arterioles. Vascular resistance is a result of friction as blood flows through the vessels and the smaller the diameter of the vessels the higher the resistance. The relationships among pressure, flow and resistance are quite simple: • Pressure = flow X resistance

  5. Kidney – Blood Pressure Relationship • By regulating the total volume of the extracellular fluid (ECFV), kidneys control blood volume. • If ECFV and blood volume increases, blood pressure increases • ECFV is regulated, in large part, by total body sodium levels, which are regulated by variable sodium excretion in urine.

  6. Sodium Transport • Sodium ion (Na+) balance determines ECFV, blood volume and blood pressure • To stay in balance, Na+ eaten must equal Na+ lost – most Na+ is lost in urine. • 70% of Na+ is reabsorbed in the proximal tubule • Fine regulation of Na+ excretion takes place in the distal tubule and collecting ducts

  7. Hormones Regulate Sodium Balance • The renin-angiotensin system (RAAS) regulates sodium excretion. Angiotensin II and aldosterone both increase sodium reabsorption from the distal tubule and the collecting ducts of the nephron. • The RAAS is activated by reduced blood volume or low blood sodium concentration

  8. Water Balance • Water is added to the ECF by drinking and oxidative metabolism. It is lost mostly in expired air, sweat and urine. • The amount of water lost in urine is controlled by the antidiuretic hormone vasopressin. Vasopressin decreases urinary water loss. • Vasopressin levels increase in response to dehydration, blood loss and angiotensin II.

  9. Treatment Of Hypertension- Drugs That Target Kidney Function • Diuretics such as Lasix – Block sodium reabsorption and increases urine volume • Spironolactone and Eplerenone block aldosterone action • ACE inhibitors block conversion of Angiotensin I to angiotensin II • Losartan blocks binding of angiotensin II to cellular receptors

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