Long term control of blood pressure

Question 1

What are the functions of the kidneys?

Answer 1

Excretion of waste produces
Maintenance of ion balance
Regulation of pH
Regulation of osmolarity
Regulation of plasma volume -> regulates MAP

Question 2

What does the control of blood pressure revolve around?

Answer 2

Control of plasma volume by the kidney

Question 3

What are the main sensors for the kidneys?

Answer 3

Cardio-pulmonary baroreceptors

Question 4

What are the 3 hormone systems involved in blood pressure control?

Answer 4

• Renin-antiotensin-aldosterone system
• Antidiuretic system
• Atrial natriuretic peptide

Question 5

What does the renin-angiotensin-aldosterone system do?

Answer 5

Angiotension II causes arteriolar constriction and an increase in TPR
Aldosterone increases Na+ reabsorption -> increase in plasma volume

Question 6

What does antidiuretic factor do?

Answer 6

ADH, vasopressin
Causes arteriolar constriction and an icnrease in TPR
Increase in water permeability of collecting duct -> increase in plasma volume

Question 7

What does atrial natriuretic peptide do?

Answer 7

Causes arteriolar dilation -> decrease in TPR

Increase in Na+ excretion (natriuresis) -> decrease in blood volume

Question 8

What receptors detect blood volume? Where are they?

Answer 8

Low pressure baroreceptors

In large systemic veins and in the walls of the right atrium and ventricle

Question 9

What are the two factors that determine how much water is lost in the renal system?

Answer 9

Control over Na+ transport -> size of osmotic gradient

Control over permeability of collecting duct to water-> determines if water follows osmotic gradient or not

Question 10

How does the normal loop of Henle and distal tube operate?

Answer 10

Progressively higher concentration of salt as flow does down the descending limb -> water will try to follow the concentration gradient

Question 11

What happens when the tube is very permeable?

Answer 11

Very small volume of hyperosmotic urine

Question 12

What happens when the tube is very impermeable?

Answer 12

Large volume of hypoosmotic urine

Question 13

Where is renin produced from? What is it?

Answer 13

Juxtaglomerular (granule cells) in kidney

Precursor enzyme

Question 14

What is renin production triggered by?

Answer 14

Activation of sympathetic nerves to juxtaglomerular appartus
Decreased distension of afferent arterioles -> renal baroreflex
Decreased delivery of Na+/Cl-
All of these are signs of low MAP

Question 15

What does renin do?

Answer 15

Converts inactive angiotensin to angiotensin I

Angiotensin -> angiotensin II by converting enzyme angiotensin converting enzyme

Question 16

What does angiotensin II do?

Answer 16

Stimulates release of aldosterone from adrenal cortex -> increases Na+ reabsorption in the loop of Henle -> reduces diuresis and increases plasma volume
Increases release of ADH from pituitary -> increases water permeability of the collecting duct, reduces diuresis and increases plasma volume -> increases sense of thirst
All these increase MAP

Question 17

What is the effect of angiotensin II?

Answer 17

Vasoconstrictor, snti-natriuretic peptide
Increases TPR
Hypertrophic agent -> stimulates myocyte and smooth muscle hypertrophy in the arterioles -> poor prognostic indicators in patients with hypertension

Question 18

How is angiotensin II a negative feedback system?

Answer 18

Multiple mechanisms detect any decrease in MAP
Stimulates release of renin
Evokes multiple mechanisms which increase MAP

Question 19

Where is the antidiuretic factor produced?

Answer 19

Hypothalamus -> released form posterior pituitary

Question 20

What is antidiuretic production triggered by?

Answer 20

Decreased in blood volume -> as sensed by cardiopulmonary baroreceptors and relayed via medullary cardiovascular centres
Increase in osmolarity of the interstitial fluid -> as sensed by osmoreceptors in the hypothalamus
Circulating angiotensin II -> triggered by the renin-angiotensin-aldosterone system

Question 21

What does ADH do?

Answer 21

Increases the permeability of the collecting duct to H2O -> reduces diuresis and increases plasma
Causes vasoconstriction -> increasing MAP
Overall increase in MAP

Question 22

How does ADH work as a negative feedback system?

Answer 22

Multiple mechanisms detect any decrease in MAP
Stimulates release in ADH
Evokes multiple mechanisms which increase MAP

Question 23

Where is brain natriuretic peptide prodominantly found?

Answer 23

Ventricles but it was found in the brain first

Question 24

Where is ANP produced?

Answer 24

Myocardial cells in the atria

Question 25

What is ANP triggered by?

Answer 25

Increased distension of the atrium -> sign of increased MAP

Question 26

What does ANP do?

Answer 26

Increases excretion of Na+ (natriuresis)
Inhibits the release of renin
Acts on medullary CV ventres to reduce MAP
All tend to decrease MAP

Question 27

How does ANP act as a negative feedback system?

Answer 27

A mechanism that detects any increase in MAP
Stimulates release of ANP
Evokes multiple mechanisms which reduce MAP

Question 28

What is the rational basis for Ca2+ channel antagonists treatment?

Answer 28

Voltage gates Ca2+ channels affects the plateau in heart in AP and smooth muscle

Question 29

What is the rational basis for β-adrenoreceptor antagonists treatment?

Answer 29

Reduces CO, lowers MAP

Question 30

What is the rational basis for thiazide diuretics treatment?

Answer 30

Stops sodium transport which means more water is excreted

Question 31

What is the rational basis for angiotensin converting enzyme inhibitor treatment?

Answer 31

Stop effects on blood vessels and kidneys