Long Term Control of BP

Question 1

What is long term blood pressure control probably not controlled by?

Answer 1

Arterial baroreflex

Question 2

What three hormone systems does the long term control of BP rely on?

Answer 2

• Renin-angiotensin-aldosterone system - Antidiuretic factor (ADH and Vasopressin) - Atrial natriuretic peptide

Question 3

What structure is responsible for the long term control of BP?

Answer 3

Kidney

Question 4

What are the main functions of the kidney?

Answer 4

• Excretion of waste - Maintenance of ion balance - Regulation of pH - Regulation of osmolarity - Regulation of plasma volume

Question 5

Which of the kidney functions is used to regulate MAP?

Answer 5

• Regulation of plasma volume

Question 6

Describe what is going on here

Answer 6

• 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

Question 7

How does the renal counter current system ensure that waste moves into the collecting duct to regulate plasma volume?

Answer 7

Creates a very high osmolarity outside the collecting duct

Question 8

What controls the osmolarity gradient across the collecting duct?

Answer 8

• 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

Question 9

What will making the collecting duct very permeable to water result in?

Answer 9

• Lots of water reabsorption
• Little urine
• Conserved plasma volume

Question 10

What will making the collecting duct impermeable to water result in?

Answer 10

• Little water reabsorption
• Lots of urine (diuresis)
• Reduction in plasma volume

Question 11

Where is renin produced?

Answer 11

• Juxtaglomerular cells (granule cells)

Question 12

What will trigger renin production?

Answer 12

• Activation of sympathetic nerve to juxtaglomerular apparatus
• Decreased distention of afferent arterioles (renal baroflex)
• Decreased delivery of NaCl through the tube

Question 13

What will cause a reduced NaCl?

Answer 13

• Reduced arterial pressure in glomerulus

Question 14

What are all three renin triggers caused by?

Answer 14

Decreased mean arterial pressure

Question 15

What does renin do?

Answer 15

Converts inactive angiotensin to angiotensin I

Question 16

What happens to angiotensin I after conversion through renin?

Answer 16

Converted through angiotensin II by angiotensin converting enzyme (ACE)

Question 17

What does angiotensin II do?

Answer 17

• Stimulates release of aldosterone from adrenal cortex
• Increases release of ADH from pituitary
• Acts as a vasoconstrictor therefore increase TPR

Question 18

What does the release of aldosterone from the adrenal cortex cause?

Answer 18

• Increased Na+ reabsorption from loop of Henle
• This reduces diuresis and increase plasma volume

Question 19

What does the release of ADH from the pituitary cause?

Answer 19

• Increases water permeability of collecting duct
• Reduces diuresis and increases plasma volume
• Increases sense of thirst

Question 20

What type of feedback is the renin-angiotensin-aldosterone system?

Answer 20

Negative feedback

Question 21

Where is ADH synthesised and released?

Answer 21

Synthesised in Hypothalamus and released in pituitary

Question 22

Apart from angiotensin II what causes the release of ADH?

Answer 22

• Decrease in blood volume (sensed by baroreceptors)
• Increase in osmolarity of interstitial fluid

Question 23

What receptors sense a change in interstitial fluid osmolarity?

Answer 23

Osmoreceptors

Question 24

What other effect does ADH have on the circulation?

Answer 24

• Vasoconstriction (it’s alternate name is vasopressin)
• This increases MAP

Question 25

Where is atrial natriuretic peptide produced?

Answer 25

Myocardial cells in the atria

Question 26

What triggers the release of atria natriuretic peptide?

Answer 26

Increase atrial distention

Question 27

What does atrial natriuretic peptide do?

Answer 27

• Increases Na+ excretion (natriuresis)
• Inhibits release of renin
• Acts on medullary CV centre to reduce MAP

Question 28

What type of feedback are ALL responses to low MAP?

Answer 28

ALL negative feedback

Question 29

How do drugs used to treat hypertension usually work through?

Answer 29

• Ca2+ channels antagonists
• B-adrenoreceptor antagonists
• Thiazide diuretics
• Angiotensing converting enzyme inhibitors