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Cardio > Long term control of BP > Flashcards

Long term control of BP Flashcards

1
Q

What is the primary difference between long term & short term control of Blood pressure?

A

Short term revolves primarily around the baroreceptor reflex

Long term control probably does not involve this reflex

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2
Q

What is the basic idea of long term blood pressure control?

A

Based mainly on the volume of plasma in the blood

Controlled by the kidney, using at least 3 hormone systems

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3
Q

What hormone systems are utilised to control long term blood pressure?

A

Renin-angiotensin-aldosterone system

Antidiuretic factor (ADH, vasopressin)

Atrial natriuretic peptide

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4
Q

What are the functions of the kidneys?

A

Excretion, and regulation

Excrete waste products 
Maintain ion balance 
Regulate pH 
Regulate osmolarity 
Regulate plasma volume
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5
Q

How can kidneys alter Mean arterial pressure?

A

By altering plasma volume

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6
Q

In the kidneys, exchange of fluid with capillaries takes place at several stages/areas

Describe the different stages/types of fluid exchange

A

Filtration:

  • Takes place in the Glomerulus , in the Bowman’s capsule
  • Moves OUT of blood, into lumen - LOSS

Secretion:

  • Peritubular capillaries into proximal tube
  • Capillaries into Distal tube
  • Capillaries into Collecting duct
  • LOSS

Reabsorption:

  • Proximal tube into peritubular capillaries
  • Loop of Henle into capillaries
  • Distal tube into capillaries
  • Collecting duct into capillaries
  • GAIN
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7
Q

How does the kidney control the amount of water lost in urine?

A

Collecting duct generates a very high osmolarity outside of it

How?

  • Controlling Na+ transport
  • It can hence vary osmolarity ∴ vary the size of the osmotic gradient

It can also control the permeability of the collecting duct to water ∴ determines if water will follow the osmotic gradient or not

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8
Q

Describe how the kidneys would conserve water

A

By making the collecting duct VERY permeable to water

∴ very easy for water to move out the CD, down osmolarity gradient

This will cause lots of reabsorption ∴ extracts lots of water from kidney ∴ less leaves the end to be excreted

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9
Q

Describe how the kidneys would excrete more water

A

By reducing the permeability of the collecting duct to water

Lower permeability = less reabsorption ∴ more water in the collecting duct

∴ more water excreted as urine
∴ Diuresis

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10
Q

What effect will increased permeability of the collecting duct to water have on blood volume?

A
  • Increased volume of blood -

Higher permeability ∴ high reabsorption ∴ more water LEAVES the CD/kidney ∴ increase Plasma volume

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11
Q

What will the urine be like if the collecting duct is very permeable?

A

Small volume of hyper-osmotic pish

Hyper-osmotic = very concentrated

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12
Q

What can trigger the Renin-angiotensin-aldosterone system?

A

1) Sympathetic neurones, activated by the CVCC when blood pressure drops, link directly to granular cells
2) Granular cells in the kidneys are directly sensitive to BP ∴ respond to low pressure in renal afferent arterioles
3) Paracrine feedback from Maculla densa in the distal tubule. Reduced delivery of Na+/Cl- signals drop in MAP

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13
Q

What is the effect of triggering the Renin-angiotensin-aldosterone system?

A

Renin production

From juxtaglomerular (granular) cells of the kidney

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14
Q

Describe the how a drop in blood pressure causes renin production via the paracrine route (Na+/Cl-)

A

The Macula densa communicates with granular cells based on how much fluid flows through the distal tubule

When fluid volume is high, the Na+/Cl- delivery is high, so the MD releases paracrine signals that inhibit renin release

When low, the amount of Na+/Cl- delivery is reduced, so the MD releases other paracrine signals to stimulate renin production & release

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15
Q

Where exactly is the Macula densa?

A

Loop of Henle ascending limb

In the distal tubule of the kidney

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16
Q

What does renin do?

A

Converts inactive Angiotensinogen into Angiotensin I (ANG I)

17
Q

Describe the pathway of the reactions involving Angiotensin proteins that is kicked off by Renin

A

Angiotensinogen (an inactive plasma protein, constantly produced by the liver) is turned to ANG I by Renin

Angiotensin I (ANG I) encounters the ACE enzyme in the blood into ANG II

18
Q

What does Angiotensin II do?

A

Stimulates release of Aldosterone from the adrenal cortex

Increases the synthesis of ADH (vasopressin) in the Hypothalamus & release from the posterior pituitary gland

Causes vasoconstriction of arterioles

ALSO:

  • CVVC - triggers Cardiovascular response to increase BP
19
Q

ANG II stimulates release of Aldosterone from the AC

What does aldosterone do?

A

Increases Na+ reabsorption in the Loop of Henle

∴ reduces diuresis & increases plasma volume

20
Q

ANG II stimulates release of ADH from the pituitary gland

What does ADH do?

A

Increases water permeability of the collecting duct

∴ reduces diuresis & increases plasma volume

It is also involved in triggering the sensation of thirst

21
Q

What type of system is the R-A-A system?

A

Negative feedback system

Multiple mechanisms detect a drop in BP
Stimulates release of renin
Renin release decreases as BP becomes more normal

22
Q

What is ADH?

A

Anti-diuretic hormone

AKA vasopressin

23
Q

What triggers the release of ADH?

A

Decreased blood volume - cardiopulmonary baroreceptors relay this info to medullary CVCs

Increased osmolarity of interstitial fluid - measured by osmoreceptors in the hypothalamus

ANG II in blood

24
Q

What does ADH do?

A

Increases permeability of collecting duct to water

Vasoconstriction

(another -ve feedback system)

25
Q

What is ANP?

A

Atrial natriuretic peptide

Produced in & released from myocardial cells in the atria, triggered by increased atrial distension

Increased Atrial distension = increased MAP

∴ ANP produces in response to increased BP

26
Q

What does ANP do?

A

Increases excretion of Na+ - Natriuresis

Inhibits release of Renin

Acts of medullary CV centres to reduce MAP

27
Q

So what is the primary difference between the RAA system & the ANP system?

A

RAA - increases BP

ANP - decreases BP

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