Long term control of BP

Question 1

What is long term control of blood pressure mediated by?

Answer 1

• revolves around the control of plasma volume by the kidney and involves 3 horemone systems
• Renin-angiotensin-aldersterone system
• Antidiuretic factor ( ADH, vasopressin)
• atrial natriuretic peptide

Question 2

State the functions fo the kidney

Answer 2

• extrection of waste products
• maintainence of ion balance
• regulation of pH
• regulation of osmolarity
• regulation of PV ( used to regulate MAP)

Question 3

Describe the regulation of PV by the kidneys

Answer 3

-Starling’s forces= balance between hydrostatic pressure and osmotic pressure.

• countercurrent system creates high OSMOLARITY outside the collecting duct
• control over the Na+ transport determines how big the osmotic gradient is
• control over the permeability of the collecting duct to water determines if water follows that osmotic gradient or not
• hence, you can control how much water is lost in the urine + how much is retained

Question 4

The effect of making the collecting duct permeable to water + vise versa

Answer 4

• lots of water reabsorption, little urine and increases PV. Small volume of hyperosmotic(concentrated) urine.
• making collecting duct impermeable to water will result in little reabsorption + lots of urine ( diuresis) and reduction in PV. Large volume of hypo-osmotic(less concentrated) urine

Question 5

Where is renin produced?

Answer 5

-from juxtaglomerular ( granule cells) of the kidney

Question 6

What triggers renin production?

Answer 6

Low MAP

• juxtaglomerular apparatus is activated by sympathetic nerves.
• decreased distension of afferent arterioles ( the renal baroreflex),
• decreased delivery of Na+/Cl- through the tubule

All of this are signs of low MAP

Question 7

Function of renin

Answer 7

converts inactive angiotensin>angiotensin l

- this is is converted into Angiotensin ll by angiotensin converting enzyme

Question 8

Function of angiotensin ll

Answer 8

Stimulates the release of aldesterone from the adrenal cortex;
-this increases Na+ reasborption in the loop of Henle, hence reduces diuresis and icnreases PV

Increases release of ADH from posterior pituitary gland

• increases water permeability of the collectig duct, hence reducing diuresis and icnreases PV
• increases thirst

All of the above increases MAP

Vasoconstriction
-increases TPR

Question 9

Is the renin-angiotensin-aldersterone system a negative or positive feedback system?

Answer 9

-negative feedback system as multiple mechanisms detect any decrease in MAP, stimulates release of renin which evokes mechanisms to increase MAP

Question 10

Where is ADH produced?

Answer 10

• synthesised in the hypothalamus

- released from posterior pituary gland

Question 11

What triggwea ADH release?

Answer 11

• decrease in blood volume ( sensed by cardiopulmonary baroreceptors and relayed via the medullary cardiovascular centres)
• an increase in osmolarity of ISF ( sensed by smoreceptors of hypothalamus)
• circulating angiotensin ll ( triggered by renin-angiotensin -alderesterone system)

All of the above are signs of low PV and/or MAP

Question 12

Function of ADH

Answer 12

• increases permeability of collecting duct to H20 + reduces diuresis and increases PV
• causes vasoconstriction (hence aka vasopressin)

Both increases MAP
-another negative feedback system as many systems decrease any decrease in MAP>ADH> multiple mechanisms activated to increase MAP

Question 13

Where is atrial natriutetic peptide produced?

Answer 13

ANP produced in and releleased from myocardial cells in atria

Question 14

What triggers ANP release?

Answer 14

increased distension of atrium

A sign of increased MAP

Question 15

Function of ANP

Answer 15

• increases excretion/secretion of Na( natriuresis)
• inhibits release of renin
• acts on medullary CV centres to reduce MAP

All of these decreases MAP

Question 16

Negative feedback of ANP

Answer 16

detects increase in MAP > ANP > evokes multiple mechanisms to reduce MAP

Question 17

Identify receptors involved in sensing plasma volume (BP indirectly)

Answer 17

• cardiopulmonary receptors
• juxtaglomerular cells of the kidney
• macula densa cells of the kidney ( cells of distal convulated tubule, part of juxtaglomerular apparatus where DCT meets with afferent arteriole)

Question 18

Describe how chronic hypotension results in right sided heart failure

Answer 18

Pulmonary hypotension incolves there being high blood pressure in the pulmonary arterioles, so this high so not all the blood pumped in the right ventricle will go into pulmonary circulation as it requries more strength/energy to overcome this increased pressure. Hence, increased afterload occurs and overtime the right ventricle will adapt through hypetrophy but this may not be enough which will decrease SV + Pooling of the blood will occur into the systemic pulmonary circulation.
-Symptoms include a leg oedema, hepatomegaly,, raised JV[

Question 19

How can this lead to left side heart failure?

Answer 19

Due to pooling of blood in pulmonary circualtion, less blood will be getting pumped into the systemic circulation, increasing volume and pressure in pulmonary circulation.
-caused by acute MI, mitral valve regugitation, etc

Question 20

Why can right sided HF lead to a pulmonary oedema

Answer 20

due to high pulmonary pressure, leakage of ISF of pulmonary capillaries into the lungs will occur . Fluid accumulates in intersitial space=pulmonary oedema
-there is an imbalance of starling’s forces

Question 21

What is starling’s forces

Answer 21

-balance betweeen hydrostatic pressure and osmotic pressure

Question 22

How does an oedema affect gas exchange?

Answer 22

-fluid build up will decrease the diffusion distance thus decreasing gas exchange. Affects mainly O2 as it is less soluble in water vs CO2