long term control of blood pressure Flashcards
What is changed in order to control plasma volume in the long term?
The control of plasma volume by the kidneys
What are the three hormone systems used to control blood pressure long term?
Renin-angiotensin-aldosterone system, antidiuretic factor (vasopressin), atrial and brain natriuretic peptide
What are the functions of the kidneys?
Excretion of waste products, regulation of ion balance, pH, osmolarity, plasma volume
What determines how big the osmotic gradient is in the collecting duct?
The control over Na+ transport
What determines whether water flows down the osmotic gradient in the collecting duct?
The permeability of the collecting duct to water
What happens to the urine when the collecting duct is very permeable to water?
Results in lots of water reabsorption, small volume of hyperosmotic urine and conservation of plasma volume
What happens to urine when the collecting duct is very impermeable to water?
Little reabsorption of water so lots of hypo-osmotic urine and a reduction in plasma volume
What s diuresis?
The production of a large volume of urine
Where is renin produced?
The juxtaglomerular (granular cells) of the kidney
What 3 things trigger Renin production?
Activation of sympathetic nerves to the juxtaglomerular, decreased distension of afferent arterioles (renal baroreflex), decreased delivery of NA+/CL- through the tubule
Which part of the nephron detects the decreased sodium and chloride ion concentration which causes the release of Renin?
The macula densa
What does renin do?
Converts inactive angiotensinogen into angiotensin I. this angiotensin I is then converted into angiotensin II by angiotensin converting enzyme (ACE).
What does angiotensin II do?
Stimulates the release of aldosterone from the adrenal cortex, increases the release of ADH from the pituitary, it is also a vasoconstrictor
What does aldosterone do?
Increases the Na+ reabsorption in the loop of Henle therefore reduces diuresis and increases plasma volume
What does an increase in ADH release do?
Increases water permeability of the collecting duct, therefore reducing diuresis and increasing plasma volume. It also increases the sense of thirst
How does renin being a vasoconstrictor affect MAP?
It increases TPR, increasing MAP
Where is ADH synthesised and released?
Synthesised in the hypothalamus and released from the posterior pituitary gland
What triggers ADH release?
– A decrease in blood volume (as sensed by cardioplumonary baroreceptors and relayed via medullary cardiovascular centres)
– An increase in osmolarity of interstitial fluid (as sensed by osmoreceptors in the hypothalamus)
– Circulating angiotensin II (triggered by the renin-angiotensin-aldosterone system)
What does ADH do?
Increases the permeability of the collecting duct to water so reduces diuresis and increases plasma volume, also causes vasoconstriction increasing MAP
Where is atrial natriuretic peptide (ANP) produced?
The myocardial cells of the atria
Where is brain natriuretic peptide (BNP) released from?
The myocardial cells of the ventricles
What triggers the release of ANP and BNP?
Increased distension of the atria for ANP and ventricles for BNP
What do ANP and BNP do?
Increase the excretion of Na+ from (natriuresis), Inhibits the release of renin, Acts on medullary CV centre to reduce MAP (all these reduce MAP)
What are some classes of anti-hypertensive drugs?
– Ca2+ channel antagonists
– beta-adrenoceptor antagonists
– Thiazide diuretics
– Angiotensin converting enzyme inhibitors
