Long term control of blood pressure Flashcards
What are the functions of the kidneys?
Excretion of waste produces Maintenance of ion balance Regulation of pH Regulation of osmolarity Regulation of plasma volume -> regulates MAP
What does the control of blood pressure revolve around?
Control of plasma volume by the kidney
What are the main sensors for the kidneys?
Cardio-pulmonary baroreceptors
What are the 3 hormone systems involved in blood pressure control?
- Renin-antiotensin-aldosterone system
- Antidiuretic system
- Atrial natriuretic peptide
What does the renin-angiotensin-aldosterone system do?
Angiotension II causes arteriolar constriction and an increase in TPR
Aldosterone increases Na+ reabsorption -> increase in plasma volume
What does antidiuretic factor do?
ADH, vasopressin
Causes arteriolar constriction and an icnrease in TPR
Increase in water permeability of collecting duct -> increase in plasma volume
What does atrial natriuretic peptide do?
Causes arteriolar dilation -> decrease in TPR
Increase in Na+ excretion (natriuresis) -> decrease in blood volume
What receptors detect blood volume? Where are they?
Low pressure baroreceptors
In large systemic veins and in the walls of the right atrium and ventricle
What are the two factors that determine how much water is lost in the renal system?
Control over Na+ transport -> size of osmotic gradient
Control over permeability of collecting duct to water-> determines if water follows osmotic gradient or not
How does the normal loop of Henle and distal tube operate?
Progressively higher concentration of salt as flow does down the descending limb -> water will try to follow the concentration gradient
What happens when the tube is very permeable?
Very small volume of hyperosmotic urine
What happens when the tube is very impermeable?
Large volume of hypoosmotic urine
Where is renin produced from? What is it?
Juxtaglomerular (granule cells) in kidney
Precursor enzyme
What is renin production triggered by?
Activation of sympathetic nerves to juxtaglomerular appartus
Decreased distension of afferent arterioles -> renal baroreflex
Decreased delivery of Na+/Cl-
All of these are signs of low MAP
What does renin do?
Converts inactive angiotensin to angiotensin I
Angiotensin -> angiotensin II by converting enzyme angiotensin converting enzyme
What does angiotensin II do?
Stimulates release of aldosterone from adrenal cortex -> increases Na+ reabsorption in the loop of Henle -> reduces diuresis and increases plasma volume
Increases release of ADH from pituitary -> increases water permeability of the collecting duct, reduces diuresis and increases plasma volume -> increases sense of thirst
All these increase MAP
What is the effect of angiotensin II?
Vasoconstrictor, snti-natriuretic peptide
Increases TPR
Hypertrophic agent -> stimulates myocyte and smooth muscle hypertrophy in the arterioles -> poor prognostic indicators in patients with hypertension
How is angiotensin II a negative feedback system?
Multiple mechanisms detect any decrease in MAP
Stimulates release of renin
Evokes multiple mechanisms which increase MAP
Where is the antidiuretic factor produced?
Hypothalamus -> released form posterior pituitary
What is antidiuretic production triggered by?
Decreased in blood volume -> as sensed by cardiopulmonary baroreceptors and relayed via medullary cardiovascular centres
Increase in osmolarity of the 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 H2O -> reduces diuresis and increases plasma
Causes vasoconstriction -> increasing MAP
Overall increase in MAP
How does ADH work as a negative feedback system?
Multiple mechanisms detect any decrease in MAP
Stimulates release in ADH
Evokes multiple mechanisms which increase MAP
Where is brain natriuretic peptide prodominantly found?
Ventricles but it was found in the brain first
Where is ANP produced?
Myocardial cells in the atria
What is ANP triggered by?
Increased distension of the atrium -> sign of increased MAP
What does ANP do?
Increases excretion of Na+ (natriuresis)
Inhibits the release of renin
Acts on medullary CV ventres to reduce MAP
All tend to decrease MAP
How does ANP act as a negative feedback system?
A mechanism that detects any increase in MAP
Stimulates release of ANP
Evokes multiple mechanisms which reduce MAP
What is the rational basis for Ca2+ channel antagonists treatment?
Voltage gates Ca2+ channels affects the plateau in heart in AP and smooth muscle
What is the rational basis for β-adrenoreceptor antagonists treatment?
Reduces CO, lowers MAP
What is the rational basis for thiazide diuretics treatment?
Stops sodium transport which means more water is excreted
What is the rational basis for angiotensin converting enzyme inhibitor treatment?
Stop effects on blood vessels and kidneys
