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
