Long Term Control of Blood Pressure Flashcards
Long term control of blood pressure revolves around
Control of plasma volume by the kidney
3 hormone systems involved
Renin-angiotensin-aldosterone system Antidiuretic factor (ADH, vasopressin) Atrial natriuretic peptide
Functions of the kidney
Excretion of waste products
Regulation of plasma volume
Maintenance of ion balance
Regulation of pH and osmolality
Function of loop of Henle
Pump sodium ions out to create a concentration (osmotic) gradient which controls how much water is absorbed into the blood
Function of renal counter-current system
Creates a very high osmolality outside the collecting duct
What determines if water follows the osmotic gradient at kidneys or not
The permeability of the collecting duct to water
Where is renin produced
Juxtaglomerular (granule cells) of the kidney
Triggers for renin production (=signs of low MAP)
Activation of sympathetic nerves to the juxtaglomerular apparatus Decrease distension (dilation) of afferent arterioles (renal baroreflex) Decreased delivery of sodium/chlorine ions through the tubule
Function of renin
Converts active angiotensinogen to angiotensin I - then converted by angiotensin converting enzyme to angiotensin II
Functions of angiotensin II
Stimulates release of aldosterone from the adrenal cortex
Increases release of ADH from pituitary
Is a vasoconstrictor
Effect of aldosterone release by angiotensin II
Increases sodium ion reabsorption in the loop of Henle which reduces diuresis and increases plasma volume
Effect of increasing ADH release by angiotensin II
Increase water permeability of collecting duct which reduced diuresis and increases plasma volume, and increases sense of thirst
Effect of vasoconstriction by angiotensin II
Increases TPR
Where is ADH synthesised
Hypothalamus
Where is ADH released from
Posterior pituitary
What triggers ADH release (=signs of low plasma volume and/or MAP)
Decrease in blood volume
Increase in osmolality of ISF
Circulating angiotensin II
Function of ADH
Increases permeability of collecting duct to water which reduced diuresis and increases plasma volume
Causes vasoconstriction which increases TPR so MAP
Negative feedback system entails
Multiple mechanisms detect any decrease in MAP
Stimulates release of hormone
Evokes multiple mechanisms which increase MAP
Where is atrial natriuretic peptide (ANP) produced and released
Myocardial cells in atria
Trigger of ANP release (=signs of increased MAP)
Increased distension of the atrium
Diuresis
Increased production of urine
Functions of ANP
Increases excretion of sodium ions
Inhibits release of renin
Acts on medullary CV centres to reduce MAP
Effects of sustained residence in space (or bed rest)
Fools cardiopulmonary baroreceptors into thinking that there is a high plasma volume resulting in triggering a reduction in plasma volume
What percentage of hypertension is classed as secondary (due to a known cause)
5-10%
Drugs treatments for hypertension
Calcium ion channel antagonists Beta adrenoceptor antagonist Thiazide diuretics Angiotensin converting enzyme inhibitors Angiotensin II antagonist
