Long Term Control of Blood Pressure Flashcards
What does long term control of blood pressure revolve around?
The control of plasma volume by the kidneys
What three systems does long term control of BP involve?
Renin-angiotensin-aldosterone system
Antidiuretic factor
Atrial natriuretic peptide
What are the functions of the kidneys?
Excretion of waste products Maintenance of ion balance Regulation of pH Regulation of osmolarity Regulation of plasma volume
What is controlling plasma volume used to regulate?
MAP
Does the renal counter-current system create a high or a low osmolarity outside of the collecting duct?
Very high
What determines how large the osmotic gradient is?
Control over Na+ transport
What determines if water will follow the osmotic gradient or not?
Control over the permeability of the collecting duct
What does control over Na+ transport and permeability of the collecting duct allow?
Control of how much water is lost in the urine and how much is retained
What will result from making the collecting duct very permeable to water?
Lots of water reabsorption
Small volume of hyper-osmotic urine excreted
Conservation of plasma volume
What will result from making the collecting duct less permeable to water?
Little water reabsorption
Large volume of hypo-osmotic urine excreted
Reduction in plasma volume
Where is renin produced?
From the juxtaglomerular cells of the kidney
What is renin production triggered by?
Activation of sympathetic nerves to the juxtaglomerular apparatus
Decreased distension of afferent arterioles
Decreased delivery of Na+/Cl - through the tubule
All of MAP
What does renin convert?
Angiotensinogen to angiotensin I
What does angiotensin converting enzyme convert?
Angiotensin I to angiotensin II
What does angiotensin II stimulate?
Release of aldosterone from the adrenal cortex
How does angiotensin II stimulate the release of aldosterone?
By;
Increasing Na+ reabsorption in the loop of Henle
Reducing diuresis
Increasing plasma volume
How does angiotensin II increase the release of ADH from the pituitary?
Increasing water permeability of the collecting duct
Reducing diuresis
Increasing plasma volume
Increasing sense of thirst
How does angiotensin II work as a vasoconstrictor?
Increases TPR which is part of the negative feedback system which detects any decrease in MAP and will stimulate the release of renin to increase MAP
Where is antidiuretic hormone synthesised and released?
Synthesised by the hypothalamus
Released from the posterior pituitary
What is the release of antidiuretic hormone triggered by?
Decrease in blood volume
Increase in osmolarity of interstitial fluid
Circulating angiotensin II triggered by the renin-angiotensin-aldosterone system
All of the above are signs of a low plasma volume +/- MAP
What detects a decrease in blood volume?
Cardiopulmonary baroreceptors
What detects an increase in osmolarity of the interstitial fluid?
Osmoreceptors in the hypothalamus
What does ADH cause?
Increase in permeability of the collecting duct to water Reduced diuresis Increased plasma volume Vasoconstriction Increased MAP
Where is atrial natriuretic peptide produced and released from?
Myocardial cells in the atria
What triggers the release of atrial natriuretic peptide?
Increased distension of the atrium (sign of increased MAP)
What does atrial natriuretic peptide cause?
Increased excretion of Na+ (natriuresis)
Inhibits release of renin
Acts on medullary CV centres to reduce MAP
What percentage of hypertension is due to a known cause (secondary hypertension)?
5-10%
What is the majority of hypertension with no known cause classed as?
Primary or essential
