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CVS > 6. Control Of BP And Hypertension > Flashcards

6. Control Of BP And Hypertension Flashcards

1
Q

How do you calculate mean arterial BP?

A

Cardiac output * total peripheral resistance

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2
Q

How do you calculate cardiac output?

A

Stroke volume * heart rate

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3
Q

What is responsible for short term regulation of blood pressure?

A

Baroreceptor reflex

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4
Q

What are the 4 neurohumoral pathways which control BP long term

A

Renin-angiotensin-aldosterone system
Sympathetic nervous system
Antidiuretic hormone (ADH)
Atrial natriuretic peptide (ANP)

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5
Q

What is the main aim of the mechanisms for long term control of BP?

A

Controlling Na+ balance, and therefore extracellular fluid volume (including plasma)

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6
Q

What cells is renin released from?

A

Granular cells of juxtaglomerular apparatus (JGA) in the kidney

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7
Q

What 3 factors stimulate renin release?

A

Reduced NaCl delivery to distal tubule.
Reduced perfusion pressure in the kidney (detected by baroreceptors in afferent arteriole in kidney).
Sympathetic stimulation to JGA.
(SO DECREASED CIRCULATING VOLUME)

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8
Q

What are the 3 steps in the renin-angiotensin-aldosterone system?

A

Release of renin, reacts with angiotensinogen which is a plasma protein, to produce angiotensin I. ACE then converts this into angiotensin II

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9
Q

What 3 affects does angiotensin II have to increase BP

A

Vasoconstriction
Stimulates Na+ reabsorption at kidney
Stimulates aldosterone secretion from adrenal cortex

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10
Q

What are the 2 types of angiotensin II receptors, and which is the main actions via? What type of receptor are they?

A

AT1 and AT2
Main actions via AT1
GCPR

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11
Q

Give 3 sites of angiotensin II receptors, and their action

A

Arterioles - vasoconstriction
Kidney - stimulates Na+ reabsorption
Adrenal cortex - stimulates release of aldosterone

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12
Q

What cells does aldosterone mainly act on?

A

Principle cells of collecting ducts

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13
Q

What 3 things does aldosterone stimulate/activate?

A

Stimulates Na+ and water reabsorption.
Activates apical Na+ (re uptake) and apical K+ channels (secretion)
Increases basolateral Na+ extrusion via Na/K/ATPase

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14
Q

What other function does angiotensin converting enzyme (ACE) have?

A

Breaks down bradykinin, which has vasodilator actions, so this also works to help increase BP

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15
Q

What 2 drugs act of the RAAS system to reduce hypertension?

A

ACE inhibitors

Ang II receptor antagonists

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16
Q

How does sympathetic nervous system stimulation on the kidneys help to maintain BP?

A

Acts on arterioles to reduce renal blood flow and decrease GFR, so decrease Na+ excretion.
Stimulated renin release via RAAS.
Stimulated Na+ reabsorption from PCT.

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17
Q

What is the main role of antidiuretic hormone in maintaining BP? In what other ways does it also do this?

A

Formation of concentrated urine by retaining water to control plasma osmolarity - increases water reabsorption in distil nephron.
Stimulates Na+ reabsorption and causes vasoconstriction.

18
Q

What 2 things stimulate ADH release?

A

Increases in plasma osmolarity

Severe hypovolaemia

19
Q

What does atrial natriuretic peptide promote?

A

Vasodilation of afferent arteriole
Increased glomerular filtration rate
Inhibits Na+ reabsorption along nephron
So Na+ excretion

20
Q

Where is atrial natriuretic peptide synthesised and stored?

A

Atrial myocytes

21
Q

When is atrial natriuretic peptide released?

A

From atrial cells in response to stretch

22
Q

Is atrial natriuretic peptide released to increase or decrease BP?

A

Decrease, so reduced effective circulating volume inhibits the release of ANP to support BP

23
Q

What do prostaglandins do?

A

Act as vasodilators.
Enhance glomerular filtration and reduce Na+ reabsorption.
Act as a buffer to excessive vasoconstriction produced by SNS and RAAS, so are important when levels of Ang II are high.

24
Q

Where is dopamine formed and what is it formed from?

A

In the kidney, from circulating L-DOPA

25
Q

Where are dopamine receptors present?

A

Renal blood vessels and cells of proximal convoluted tubule and thick ascending limb of the loop of Henle

26
Q

What does dopamine cause to happen?

A

Vasodilation in kidneys

Reduced reabsorption of NaCL

27
Q

What is the definition of hypertension? What different stages can this be?

A

Sustained increase in BP

Stage I, II or severe

28
Q

What is primary hypertension?

A

Cause is unknown

29
Q

What is secondary hypertension?

A

Cause can be defined eg chronic renal disease, Cushing’s syndrome

30
Q

What is renovascular disease?

A

Occlusion of the renal artery (stenosis)

31
Q

How does renovascular disease lead to secondary hypertension?

A 
Occlusion of renal artery 
Fall in perfusion pressure in kidney
Increased renin production
Activation of RAAS
Vasoconstriction and Na+ retention in other kidney
32
Q

How does renal parenchyma disease (caused by chronic kidney disease) lead to secondary hypertension?

A

Early stage - loss of vasodilator substances.

Later stage - Na+ and water retention due to inadequate glomerular filtration (volume dependant hypertension).

33
Q

Give one adrenal cause of secondary hypertension and how it causes hypertension

A

Cushing’s syndrome - excess secretion of glucocorticoid cortisol, which at high concentrations acts on aldosterone receptors, leading to Na+ and water retention

34
Q

Hypertension leads to increased afterload (pressure on wall of LV during ejection). What does this result in?

A

LV hypertrophy - heart failure

Increased myocardial oxygen demand - myocardial ischaemia and MI

35
Q

Hypertension leads to arterial damage. HWat does this cause?

A

Atherosclerosis and weakened vessels - cerebro-vascular disease stroke, aneurysm, nephro-sclerosis and renal failure, retinopathy

36
Q

What target organs should be assessed in hypertension?

A

Brain, eyes, heart, kidneys, arteries

37
Q

In primary hypertension what can be used to work out possible targets for treatment?

A

Equation for mean arterial BP

38
Q

Give 3 non-pharmacological approaches for treating hypertension

A

Exercise
Reduced Na+ intake
Reduced alcohol intake
Diet

39
Q

What could limit the effectiveness of antihypertensive therapy?

A

Failure to implement lifestyle changes

40
Q

Give two types of vasodilators and how they work to treat hypertension

A

L-type Ca channel blockers - reduce Ca2+ entry to vascular smooth muscle cells, so relaxation.
Alpha1 receptor blockers - reduce sympathetic tone, but can cause postural hypotension.

41
Q

What is the main group of diuretics given to treat hypertension, and how do they work?

A

Thiazide diuretics - reduce circulating volume by inhabiting Na+ reabsorption in distal tubule

42
Q

What do beta blockers do?

A

Block beta1 receptors in the heart, to reduce effects on sympathetic output, thus reducing heart rate and contractility. Only used if other indications such as previous MI

CVS (14 decks)

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