Long term control of blood pressure Flashcards
What does long term control of blood pressure revolve around
plasma volume by the kidney
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
How does the kidneys regulate plasma volume
creates high osmolarity outside the collecting ducts
What determines the size of the osmolarity gradient
Control over Na transport
What determines if the water will follow the osmolarity gradient
Control over the permeability of the collecting duct
What would happen if you made the collecting ducts very impermeable
Less water reabsorbtion
Lots of dilute urine
Reduction in plasma volume
What would happen if you made the collecting ducts permeable
lots of water reabsorption,
little concentrated urine,
conserve plasma volume
What is the three regulating hormones that regulate the process of kidney reabsorption
Renin-angiotensin-aldosterone system Antidiuretic factor (ADH, vasopressin) Atrial natriuretic peptide
Where is Renin-angiotensin-aldosterone system produced
From the juxtaglomerular (= granule cells) of the kidney
What triggers renin production
A reduction in mean arterial pressure
How is mean arterial pressure reduced to trigger renin production
Activation of sympathetic nerves to the juxtaglomerular apparatus
Decreased distension of afferent arterioles (the “renal baroreflex”)
Decreased delivery of Na+/Cl- through the tubule to the
Where is the Na/Cl delivered through in the tubule
to macula densa
What is the action of rensin
Converts inactive angiotensinogen to angiotensin I
Which is in turn converted by angiotensin converting enzyme to angiotensin II
What is the function of angiotensin II
Stimulates release of aldosterone from the adrenal cortex Increases release of ADH from the pituitary
Acts as a vasoconstrictor - increase TPR
What is the affect of aldosterone on the kidney
Increases Na+ reabsorption in the loop of Henle
Therefore reduces diuresis and increases plasma volume
What is the affect of ADH on the kidney
Increases water permeability of the collecting duct
Therefore reduces diuresis and increases plasma volume
And increases sense of thirst
How is the Renin-angiotensin-aldosterone system a negative feedback system
As the Multiple mechanism detect any decrease in MAP
which stimulates release of renin
This evokes multiple mechanisms which increase MAP
Where is ADH synthesised
The hypothalamus
Where is ADH released
The posterior pituitary
What triggers the release of ADH
A decrease in blood volume
An increase in osmolarity of interstitial fluid
Circulating angiotensin II
What detects the decrease in blood volume that triggers the release of ADH
Sensed by cardioplumonary baroreceptors and relayed via medullary cardiovascular centres
What senses the increase is osmolarity interstitial fluid that stimulates the release of ADH
Sensed by osmoreceptors in the hypothalamus
What is the function of ADH
Increases the permeability of the collecting duct to H2O, therefore reduces diuresis and increases plasma volume
Causes vasoconstriction - therefore increasing MAP
What is the steps of ADH as a negative feedback system
Multiple mechanism detect any decrease in MAP
Stimulates release of ADH
This evokes multiple mechanisms which increase MAP
Where is the atrial natriuretic peptide produced and released
myocardial cells in the atria
What triggers atrial natriuretic peptide release
Increased distension of the atrium
- a sign of increased MAP
What is the overall function of atrial natriuretic peptide
Decrease plasma volume and mean arterial pressure
What is the different actions of the atrial natriuretic peptide
Increases excretion of Na+ (natriuresis)
Inhibits the release of renin
Acts on medullary CV centres to reduce MAP
What is the steps of atrial natriuretic peptide being a negative feedback system
A mechanism that detects any increase in MAP
Stimulates release of ANP
This evokes multiple mechanisms which reduce MAP
What is the two classification (and their probabilities) of hypertension
Primary - unknown cause ( ±90%)
Secondary - known underlying cause (5-10%)
The reason for hypertension is usually unknown, how is the condition treated then
By giving a rational basis for drugs treatments
What is the different drug treatments for hypertension
Ca2+ channel antagonists
-adrenoceptor antagonists
Thiazide diuretics
Angiotensin converting enzyme inhibitors
What is the affect of thiazide diuretics
make you exreet more water, prvent build up of calcium
What is the affect of Ca2+ channel antagonists
Reduce the release of calcium therefore reduce the force of contraction of the myocardium and decreasing blood pressure
What is the affect of the adrenoceptor antagonists
block the affects of the sympathetic NS, therefore decrease Heart rate and blood pressure
What is the affect of Thiazide diuretics
Preventing the build of sodium therefore reducing plasma volume there blood pressure
What is the affect of Angiotensin converting enzyme inhibitors
Decreases the production of angiotensin II which causes blood vessels enlarge or dilate therefore blood pressure is reduced
What is long term control of mean arterial pressure dependant on
hormones acting on the kidney to control plasma volume
