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CVS > 11. Control Of BP > Flashcards

11. Control Of BP Flashcards

1
Q

What is hypertension?

A

Sustained increase in blood pressure

Normal or ideal adult BP is between 90/60mmHg and 120/80mHg

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2
Q

What is the BP in stage 1 hypertension?

A

> = 140/90 mmHg

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3
Q

What is the BP in stage 2 hypertension?

A

> =160/100 mmHg

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4
Q

What is the BP in severe hypertension?

A

> = 180 systolic or >= 110 diastolic

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5
Q

What causes hypertension?

A

In about 95% of cases, cause is unknown (primary hypertension)
Where the cause can be defined it is secondary hypertension e.g. renovascular disease, chronic renal disease, hyperaldosteronism, Cushing’s syndrome

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6
Q

Why is it important to treat hypertension?

A

Silent killer
Although it can be asymptomatic, can have unseen damaging effects on heart and vasculature, leading to heart failure, MI, stroke, renal failure, retinopathy

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7
Q

What is the medium and loner term control of blood pressure?

A

Complex interaction of neurohumoral responses

Directed at controlling sodium balance and thus extracellular fluid volume

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8
Q

What are the 4 parallel neurohumoral pathways that control circulating volume and hence BP?

A

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

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9
Q

Where is renin released from?

A

Granular cells of juxtaglomerular apparatus (JGA)

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10
Q

What are the factors that stimulate renin release?

A

Reduced NaCl delivery to distal tube
Reduced perfusion pressure in kidney (detected by baroreceptors in afferent arteriole)
Sympathetic stimulation to JGA increases release of renin

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11
Q

What is the renin-angiotensin-aldosterone system?

A

Angiotensinogen converted to angiotensin 1 by renin
Angiotensin 1 converted to angiotensin 2 by ACE (angiotensin converting enzyme)
Angiotensin causes vasoconstriction, stimulates Na+ absorption at kidney and stimulates aldosterone

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12
Q

What are the 2 types of Ang 2 receptors?

A

AT1 and AT2
Main actions via AT1 receptor
G-protein coupled receptor

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13
Q

What are the actions of aldosterone on the kidney?

A

Acts on principal cells of collecting ducts
Stimulates Na+ and therefore water reabsorption
Activatesapical na+ channels and apical K+ channel
Also increases base lateral Na+ extrusion via Na/K/ATPase

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14
Q

What does bradykinin convert to?

A

Peptide fragments using angiotensin converting enzyme (ACE)

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15
Q

Where s bradykinin mainly found?

A

In the lungs

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16
Q

Describe ACE inhibitors

A

ACE inhibitors prevent ACE from working and therefore angiotensin 1 cannot convert to angiotensin 2 and bradykinin cannot convert to peptide fragments
E.g. captopril, lisinopril, perindopril, enalapril

17
Q

How does the sympathetic nervous system control blood volume and therefore BP?

A

High levels of sympathetic stimulation reduce renal blood flow - vasoconstriction, decrease GFR and decrease Na+ excretion
Activates apical Na/H-exchanger and basolateral Na/K ATPase in PCT
Stimulates renin release from JGcells - leading to increased Ang 2 levels and increased aldosterone levels, therefore increased Na+ reabsorption

18
Q

Describe direct sympathetic stimulation

A

Acts on arteriolar to reduce renal blood flow - vasoconstriction
Stimulates granule cells of afferent arteriole to release renin via renin-Ag-aldosterone axis
Stimulates Na+ reabsorption from PCT

19
Q

What is ADH release stimulated by?

A

Increases in plasma osmolarity or severe hypovolaemia

Stimulated with low BP as low blood volume

20
Q

What is the role of ADH?

A

Stimulates Na+ reasborption - acts on thick ascending limb, stimulates apical Na/K/Cl co-transporter
Increases water absorption in distal nephron

21
Q

How do natriuretic peptides control circulating volume and therefore BP?

A

Atrial natriuretic peptide promotes Na+ excretion
Synthesised and stored in atrial myocytes
Released from atrial cells in response to stretch
Low pressure volume sensors in atria
Reduced effective circulating volume inhibits release of ANP to support BP

22
Q

What are the actions of ANP?

A

Causes vasodilation of afferent arteriole
Increased blood flow increases GFR
Also inhibits Na+ reabsorption along nephron
Acts in opposite direction to other neurohumoral regulators - causes natriuresis (loss of Na+ into urine)
If circulating volume is low ANP release is inhibited - supports BP

23
Q

What are prostaglandins?

A

Acts as vasodilator
Enhance glomerular filtration and reduce Na+ reabsorption
Protective function
Act as bidder to excessive vasoconstriction produced by SNS and RAA system
Important when levels of Ang 2 are high

24
Q

What is dopamine?

A

Formed locally in kidney from circulating L-DOPA
Receptors present on renal blood vessels and cells of PCT and TAL
Causes vasodilation and increases renal blood flow
Reduces reabsorption of NaCl

25
Q

What is renovascular disease?

A

Occlusion of renal artery (stenosis) causes fall in perfusion pressure in kidney
Decrease perfusion pressure leads to increased renin production
Activation of renin-angiotensin-aldosterone system
Vasoconstriction and Na+ retention at other kidney

26
Q

What are the adrenal causes for secondary hypertension?

A

Conn’s syndrome - aldosterone secreting adenoma
Cushing’s syndrome - excess secretion of glucocorticosteroid cortisol
Tumour of adrenal medulla - secretes catacholamines

27
Q

What are the non-pharmacological approaches to treating hypertension?

A

Exercise
Diet
Reduced Na+ intake
Reduced alcohol intake

28
Q

How do you treat hypertension by targeting the renin-angiotensin-aldosterone system?

A

ACE inhibitors - prevents production of Ang2 from Ang1
Ang2 receptors antagonists
Blocking production or action of Ang2 has diuretic and vasodilator effects

29
Q

What can a build up of bradykinin cause?

A

Can cause dry cough

30
Q

How do you treat hypertension with vasodilators?

A

L-type Ca channel blockers - reduce Ca2+ entry to vascular smooth muscle cells, relaxation of vascular smooth muscle
Alpha 1 receptors blockers - reduce sympathetic tone, can cause postural hypotension

31
Q

How do you treat hypertension with diuretics?

A

Thiazides diuretics - reduce circulating volume

Inhibit Na/Cl co-transporter on apical membrane of cells in distal tubule

32
Q

When are beta blockers used to treat hypertension?

A

If there are other indications such as previous MI

CVS (21 decks)

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