Long Term Control of Blood Pressure

Question 1

What controls blood pressure in the long term?

Answer 1

Renin-Angiotensin-Aldosterone System (RAAS)

Question 2

What is renin?

Answer 2

A peptide hormone released by the granular cells of the juxtaglomerular apparatus in the kidney.

Question 3

What is renin released in response to?

Answer 3

Sympathetic stimulation
Reduced sodium-chloride delivery to the distal convoluted tubule
Decreased blood flow to the kidney

Question 4

What kidney function is important when discussing the long term control of blood pressure?

Answer 4

Regulation of plasma volume as controlling plasma volume is used to regulate MAP

Big plasma volume = high MAP vice versa

Question 5

What is Bowman’s Capsule?

Answer 5

A part of the nephron which is a part of your kidney. The nephron is the filtering unit of your kidney.

Question 6

What creates a very high osmolarity outside collecting duct of kidney?

Answer 6

Renal counter current system

Question 7

Control over what determines size of the osmotic gradient?

Answer 7

Na+ (sodium) transport

Question 8

Osmolarity of filtrate coming out of Bowman’s Capsule?

Answer 8

300 mOsm - same as blood

Question 9

What happens as Na+ goes down the Bowman’s capsule?

Answer 9

Na+ transported out and builds big osmotic gradient w/ increased sodium in ECF

Question 10

What happens to MAP when the collecting duct of the kidney is made very permeable to water?

Answer 10

Lots of water moves out of collecting duct
Lots of water reabsorption
Little urine and plasma volume = very small vol. of concentrated urine
Retaining water results in increased MAP due to increased plasma volume

Question 11

What happens to MAP when the collecting duct of the kidney is made impermeable to water?

Answer 11

Little water reabsorption
Decreased plasma volume
Decreased MAP

Question 12

What are the three main hormones that regulate water reabsorption?

Answer 12

Renin - angiotensin - aldosterone system (RAAS)

Antidiuretic factor (ADH, vasopressin)

Atrial natriuretic peptide

Question 13

What triggers renin production?

Answer 13

–Activation of sympathetic nerves to the juxtaglomerular apparatus

–Decreased distension of afferent arterioles (the “renal baroreflex”)

–Decreased delivery of Na+/Cl- through the tubule

ALL SIGNS OF LOW MAP

Question 14

What does renin do?

Answer 14

Converts inactive angiotensinogen to angiotensinogen I
Which is in turn converted by angiotensin converting enzyme to angiotensinogen II

Question 15

What is the active hormone in the RAAS system?

Answer 15

Angiotensinogen II

Question 16

What does angiotensinogen II do?

Answer 16

Stimulates release of aldosterone form the adrenal cortex
- Increases Na+ absorption in loop of Henle, reducing diuresis and increases PV

Increases release of ADH from the pituitary
- Increases water permeability of the collecting duct, reducing diuresis and increases PV and thirst

Vasoconstrictor therefore increases total peripheral resistance

ALL INCREASE MAP

Question 17

What type of feedback is the RAAS system?

Answer 17

Negative feedback

Question 18

What is diuresis?

Answer 18

Increased or excessive production of urine.

Question 19

Where is ADH synthesised and where is it released from?

Answer 19

S: hypothalamus
R: posterior pituitary

Question 20

What is responsible for detecting a reduced delivery of sodium and chlorine ions?

Answer 20

Macula densa

Found in the ascending loop of henle

Question 21

What triggers ADH release?

Answer 21

A decrease in blood volume - (Baroreceptors from CVS relayed by medullary cardiovascular centres)

An increase in osmolarity in interstitial fluid (osmoreceptors in the hypothalamus)

Circulating angiotensin 2 (triggered by the renin-angiotensin-aldosterone system)

ALL SIGNS OF LOW PV OR MAP

Question 22

What is the effect of ADH?

Answer 22

Increases the permability of the collecting duct to H2O

Causes vasoconstriction (hence why it is sometimes known as vasopressin)

Both tend to increase MAP

Question 23

Why is the release of ADH classed as a negative feedback mechanism?

Answer 23

–Multiple mechanism detect any decrease in MAP

–Stimulates release of ADH

–This evokes multiple mechanisms which increase MAP

Question 24

Where is ANP and BNP produced?

Answer 24

In and released from myocardial cells in the atria and the ventricles respectively

Question 25

What triggers ANP and BNP release?

Answer 25

Increased distention of the atria and ventricles

A SIGN OF INCREASED MAP

Question 26

What do ANP and BNP do?

Answer 26

Increases the excretion of sodium (natriuresis) - (opposes the act of angiotensin 2 which causes lots of sodium to be reabsorbed by the loop of henle)

Inhibits the release of renin

Acts on the medullary CV centres to reduce MAP

ALL DECREASE MAP

Question 27

Why is the release of ANP described as a negative feedback mechanism?

Answer 27

–A mechanism that detects any increase in MAP

–Stimulates release of ANP

–This evokes multiple mechanisms which reduce MAP

Question 28

What does ANP stand for?

Answer 28

Atrial natriuretic peptide

Question 29

What percentage of hypertension cases are as a result of secondary (knoown) causes?

Answer 29

Only 5% to 10%

Question 30

What are the rational drug treatments for hypertension?

Answer 30

–Ca2+ channel antagonists

–b-adrenoceptor antagonists – specifically beta 1 receptor antagonist – reduces cardiac output and blood pressure

–Thiazide diuretics – work in sodium transporter in kidney – stops build up of sodium gradient – makes you excrete more water

–Angiotensin converting enzyme inhibitors

–Angiotensin 2 antagonist