Long Term Control of BP COPY Flashcards
What is long term blood pressure control probably not controlled by?
Arterial baroreflex
What three hormone systems does the long term control of BP rely on?
- Renin-angiotensin-aldosterone system - Antidiuretic factor (ADH and Vasopressin) - Atrial natriuretic peptide
What structure is responsible for the long term control of BP?
Kidney
What are the main functions of the kidney?
- Excretion of waste - Maintenance of ion balance - Regulation of pH - Regulation of osmolarity - Regulation of plasma volume
Which of the kidney functions is used to regulate MAP?
- Regulation of plasma volume
Describe what is going on here
- Blood enters Bowman’s capsule
- Glomerular filtration takes place into the proximal tubule
- Blood enters peritubular capillaries where some fluid is reabsorbed and some is secreted
- Blood travels down nephron to loop of henle where some fluid is reabsorbed
- Blood travels back up the other side where more fluid is reabsorbed
- Blood reaches distal tubule where some fluid is reabsorbed and some is lost
- Blood leaves the nephon out of the renal vein
- Waste collected from the blood collects in the collecting duct where it goes to be excreted
How does the renal counter current system ensure that waste moves into the collecting duct to regulate plasma volume?
Creates a very high osmolarity outside the collecting duct
What controls the osmolarity gradient across the collecting duct?
- Control over Na+ transport determines the size of it
- Control over permeability of collecting duct to water determines if water follows the gradient or not
- This allows the volume of water in the urine to be controlled
What will making the collecting duct very permeable to water result in?
- Lots of water reabsorption
- Little urine
- Conserved plasma volume
What will making the collecting duct impermeable to water result in?
- Little water reabsorption
- Lots of urine (diuresis)
- Reduction in plasma volume
Where is renin produced?
- Juxtaglomerular cells (granule cells)
What will trigger renin production?
- Activation of sympathetic nerve to juxtaglomerular apparatus
- Decreased distention of afferent arterioles (renal baroflex)
- Decreased delivery of NaCl through the tube
What will cause a reduced NaCl?
- Reduced arterial pressure in glomerulus
What are all three renin triggers caused by?
Decreased mean arterial pressure
What does renin do?
Converts inactive angiotensin to angiotensin I
What happens to angiotensin I after conversion through renin?
Converted through angiotensin II by angiotensin converting enzyme (ACE)
What does angiotensin II do?
- Stimulates release of aldosterone from adrenal cortex
- Increases release of ADH from pituitary
- Acts as a vasoconstrictor therefore increase TPR
What does the release of aldosterone from the adrenal cortex cause?
- Increased Na+ reabsorption from loop of Henle
- This reduces diuresis and increase plasma volume
What does the release of ADH from the pituitary cause?
- Increases water permeability of collecting duct
- Reduces diuresis and increases plasma volume
- Increases sense of thirst
What type of feedback is the renin-angiotensin-aldosterone system?
Negative feedback
Where is ADH synthesised and released?
Synthesised in Hypothalamus and released in pituitary
Apart from angiotensin II what causes the release of ADH?
- Decrease in blood volume (sensed by baroreceptors)
- Increase in osmolarity of interstitial fluid
What receptors sense a change in interstitial fluid osmolarity?
Osmoreceptors
What other effect does ADH have on the circulation?
- Vasoconstriction (it’s alternate name is vasopressin)
- This increases MAP
Where is atrial natriuretic peptide produced?
Myocardial cells in the atria
What triggers the release of atria natriuretic peptide?
Increase atrial distention
What does atrial natriuretic peptide do?
- Increases Na+ excretion (natriuresis)
- Inhibits release of renin
- Acts on medullary CV centre to reduce MAP
What type of feedback are ALL responses to low MAP?
ALL negative feedback
How do drugs used to treat hypertension usually work through?
- Ca2+ channels antagonists
- B-adrenoreceptor antagonists
- Thiazide diuretics
- Angiotensing converting enzyme inhibitors
