Long Term Control of BP Flashcards
(29 cards)
What is long term BP controlled by?
The kidneys
List some of the general functions of the kidney.
Excretion of waste products
Maintenance of ion balance
Regulation of pH
Regulation of osmolarity
Regulation of plasma volume
Which function of the kidney is useful when trying to regulate MAP?
Controlling plasma volume
How do the kidneys regulate plasma volume?
-Renal counter-current system creates a very high osmolarity outside the collecting duct.
-Control of sodium transport determines how big osmotic gradient is.
-Control over the permeability of the collecting duct to water determines if water follows that osmotic gradient or not
-Therefore can control how much water is lost via urine and how much is retained.
Describe some of the ways you can modulate how much water is retained and how much is lost via urine.
- Modulating Na+ transport will affect how big the osmotic gradient is in the first place
- Making the collecting duct very permeable to water will result in lots of water reabsorption, little urine, and conserve plasma volume
- Making the collecting duct very impermeable to water will result in little reabsorption, lots of urine (= diuresis), and a reduction in plasma volume
What is the role of the Renin-angiotensin-aldosterone system?
Feedback system which sense disturbances in plasma volume and MAP
Which hormone does the Renin-angiotensin-aldosterone system produce?
Renin
Where is renin produced?
From the juxtaglomerular (= granule cells) of the kidney
What triggers 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
When do you get sympathetic activation?
When BP is low
If BP is low, is there more or less filtration and, as a result, delivery of calcium and sodium?
Less filtration and less delivery
What does renin do?
Converts inactive angiotensinogen to angiotensin I
What is angiotensin I converted to?
Converted by angiotensin converting enzyme to angiotensin II
What biological molecule is renin?
Enzyme
What do angiotensin II do?
Stimulates release of aldosterone from the adrenal cortex
Increases release of ADH from the pituitary
Is a vasoconstrictor and increases TPR
What does angiotensin II stimulating the release of aldosterone from the adrenal cortex do?
Increases Na+ reabsorption
Therefore reduces diuresis and increases plasma volume
What does angiotensin II increasing release of ADH do?
Increases water permeability of the collecting duct
Therefore reduces diuresis and increases plasma volume
And increases sense of thirst
If you drink more water, will it increase or decrease plasma volume?
Should increase
Where is ADH (Antidiuretic hormone) synthesised from?
Where it is then released from?
Synthesised in the hypothalamus
Released from the posterior pituitary
What can trigger ADH release?
A decrease in blood volume
An increase in osmolarity of interstitial fluid
Circulating angiotensin II
What senses a decrease in blood volume?
Sensed by cardiopulmonary baroreceptors and relayed via medullary cardiovascular centres
What sense an increase in osmolarity of interstitial fluid?
Osmoreceptors in the hypothalamus
What do the following suggest?
A decrease in blood volume
An increase in osmolarity of interstitial fluid
Circulating angiotensin II
Low plasma volume and/or MAP
What does ADH do?
Increases the permeability of the collecting duct to H2O, therefore reduces diuresis and increases plasma volume
Causes vasoconstriction, increasing MAP
