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CVS Physiology > Long term control of BP > Flashcards

Long term control of BP Flashcards

1
Q

What are the functions of the kidneys?

A

Excretion of waste products
Maintenance of ion balance
Regulation of pH
Regulation of osmolarity
Regulation of plasma volume

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2
Q

How is regulation of plasma volume important?

A

Controlling plasma volume is used to regulate MAP:
- If trying to squeeze big plasma volume through CVS = high MAP
- If trying to squeeze low plasma volume through CVS = low MAP

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3
Q

How do the kidneys regulate plasma volume? (vauge)

A

Control how much water is lost as urine and how much is retained

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4
Q

What does the renal counter-current system create?

A

A very high osmolarity outside the collecting duct

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5
Q

What determines how big the osmotic gradient outside the collecting duct is?

A

Control over Na transport

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6
Q

What determines if water flows along the osmotic gradient?

A

Control over permeability of the collecting duct to water

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7
Q

What is the efferent arteriole and what does it do?

A

Flows close to the loop of Henle and collecting duct and as things move along they can be reabsorbed or secreted
(move form blood to filtrate or back)

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8
Q

How is transfer between blood and filtrate done?

A
  • Done by kidney building up a big Na gradient in the extracellular fluid in the loop of Henle.
  • Water comes into the collecting duct, by controlling permeability, you can either allow water to follow that osmotic gradient or not.
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9
Q

Where does filtrate start and with what osmolarity?

A

Bowman’s capsule
Osmolarity of 200 milliosmoles (same as blood so no osmotic gradient)

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10
Q

What happens to osmotic gradient as filtrate passes through loop of Henle and why?

A

As it comes down the loop of Henle, Na is transported out which builds up osmotic gradient.

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11
Q

What is osmolarity of filtrate by the time it reaches collecting duct?

A

50 miliosmoles

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12
Q

What modulates the amount of water retained/reabsorbed?

A

Modulating Na transport
Making collecting duct very permeable to water
Making collecting duct impermeable

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13
Q

How can modulating Na transport affect the amount of water retained?

A

Will affect how big the osmotic gradient is in the first place

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14
Q

What happens when you make the collecting duct highly permeable to water? (fate of MAP)

A

Will result in lots of water reabsorption, little urine and conserve plasma volume
- Increase MAP

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15
Q

What happens when you make the collecting duct impermeable to water? (fate of MAP)

A

§ Little water reabsorbed an lots ending up in urine
- Large volume of very dilute urine
- Diuresis
Leads to decrease in plasma volume and decrease in MAP

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16
Q

What hormone system regulates sensing of plasma volume?

A

Renin-angiotensin-aldosterone system (RAAS)

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17
Q

What is RAAS?

A

Feedback system that senses disturbances in plasma volume and MAP.
Produces hormones to produce appropriate response.

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18
Q

What hormones does RAAS produce?

A

Renin

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19
Q

Where is renin produced?

A

Juxtaglomerular of the kidney

20
Q

What triggers renin production?

A

Activation of sympathetic nerves to the juxtaglomerular apparatus.
Decreased distension of afferent arterioles (the renal baroreflex).
Decreased delivery of Na/Cl through the tubule.

21
Q

How does activation of sympathetic nerves lead to renin production?

A

Sympathetic activation when BP is low.
Increases contractility of heart and HR.
Increases SV, CO and MAP.
Activates juxtaglomerular cells and releases renin.

22
Q

How does decreased distension of afferent arterioles lead to renin production?

A

Signalling a reduction in MAP
- If lower MAP then arterioles are less stretched/distended

23
Q

How does decreased distension of Na/Cl through the tubules lead to renin production?

A

If BP is higher = more filtration
- More Na/cl going out of proximal tube
- More Na/Cl delivered to macula densa

If BP is low = less filtration
- Less delivery of Na/Cl

Reduction in MAP and triggers release of renin

24
Q

What is the path of filtrate?

A
  • Blood comes into Bowman’s capsule from the afferent arteriole
  • Its filtered under high pressure
  • Filtrate comes out proximal tubule
  • Down descending limb of loop of Henle, off the ascending limb
  • Back down past Bowman’s capsule
  • Juxtaglomerular cells are here
25
Q

What does renin do?

A

Converts angiotensinogen into angiotensin 1

26
Q

What is angiotensin 1 converted to and by what?

A

Angiotensin 2 by angiotensin converting enzyme

27
Q

What is angiotensin 2?

A

The active hormone

28
Q

What does angiotensin 2 do?

A
  • Stimulates release of aldosterone from adrenal cortex
  • Increases release of ADH from pituitary gland
  • Is a vasoconstrictor
29
Q

What is aldosterone and what does it do?

A

A steroid hormone
- Increases Na reabsorption in the loop of Henle, giving a bigger osmotic gradient
- Recues diuresis and increases plasma volume

30
Q

What does increasing the release of ADH do?

A

Reduces diuresis and increases plasma volume
- Increase water permeability of the collecting duct
- Also increases sense of thirst

31
Q

What effect does angiotensin being a vasocontrictor have?

A

Increases TPR and thus increases MAP

32
Q

What type of system is angiotensin and why?

A

A negative feedback system
- Multiple mechanisms detect any decrease in MAP
- Stimulate release of renin
- This evokes multiple mechanisms which increase MAP

33
Q

What does ADH mean?

A

Antidiuretic hormone

34
Q

Where is ADH synthesised?

A

Hypothalamus

35
Q

Where is ADH released?

A

Posterior pituitary gland into the blood stream

36
Q

What triggers ADH release?

A

Decrease in blood volume
Increase in osmolarity if ISF
Circulating angiotensin 2

37
Q

What does ADH do?

A

Increases permeability of collecting duct to water reducing diuresis and increasing plasma volume and MAP
Causes vasoconstriction and therefore increases MAP

38
Q

What type of system is ADH?

A

Negative feedback system
- Multiple mechanisms detect any decrease in MAP
- Stimulate release of ADH
- This evokes multiple mechanisms which increase MAP

39
Q

What do ANP and BNP stand for?

A

ANP = atrial natriuretic peptide
BNP = brain natriuretic peptide

40
Q

Where are ANP and BNP produced and released?

A

ANP = myocardial cells
BNP = ventricles

41
Q

What triggers the release of ANP/BNP?

A

Increased distension of the atria and ventricles (a sign of increased MAP)

42
Q

What do ANP and BNP do?

A
  • Increase excretion of Na (natriuresis)
  • Inhibit the release of renin
  • Act on medullary CV centres to reduce MAP

*All tend to reduce MAP

43
Q

What type of system are ANP and BNP?

A

Negative feedback system but decreasing MAP
- A mechanism detects any increase in MAP
- Stimulates release of ANP and BNP
- This evokes multiple mechanisms which reduce MAP

44
Q

What proportion of hypertension cases are primary/secondary?

A

Primary = 95-90%
Secondary = 5-10%

45
Q

What are some types of drug that can be used for hypertension? (5)

A
  • Ca2+ channel antagonists
  • B-adrenoreceptor antagonists
  • Thiazide diuretics
  • Angiotensin converting enzyme inhibitors
  • Angiotensin 2 antagonists

CVS Physiology (10 decks)

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