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Cardiovascular > Control Of Blood Pressure > Flashcards

Control Of Blood Pressure Flashcards

1
Q

What is hypertension?

A

Sustained increase in blood pressure

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2
Q

What is blood pressure measured in?

A

MmHg

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3
Q

What is the normal or ideal adult blood pressure considered to be between ?

A

90/60mmHg and 120/80mmHg

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4
Q

What causes hypertension? ( primary and secondary)

A
  • in around 95% of cases , the cause is unknown. This is called primary hypertension.
  • in the remaining 5% , this can be called secondary hypertension where the causes are often : renal vascular diseases , renal chronic disease , hyperaldosteronism,Cushing syndrome
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5
Q

Stage 1 hypertension values

A

Above 140/90 mmHg

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6
Q

Stage 2 hypertension

A

160/100mmHg

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7
Q

Severe hypertension

A

180/110

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8
Q

Why is it important to treat hypertension?

A
  • the silent killer
  • it can have unseen damaging effects on the heart and vasculature.
  • potentially leading to heart failure , MI, stroke , renal fialure and retinopathy.
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9
Q

What are a few diseases that result from hypertension?

A
  • heart failure
  • coronary heart disease
  • stroke
  • MI
  • left ventricular hypertrophy
  • aortic aneurysms
  • chronic kidney fialure
  • cerebral hemorrage
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10
Q

How can hypertension lead to heart failure ?

A

1) due to the increased afterload, the left ventricle must work harder to eject blood.
2) this causes left ventricular hypertrophy
3) this results in heart failure

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11
Q

How can hypertension lead to MI?

A

1) due to the increased afterload , there is an increase in the myocardial demand for oxygen - which cannot be supplied. This leads to myocardial ischaemia.
2) Or hypertension could lead to arterial damage which leads to atherosclerosis forming which could prevent oxygenated blood from supplying the myocardium.

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12
Q

What does arterial damage result iN.

A

1) atherosclerosis and weakened vessels
- this leads to aneurysms
- retinopathy

  • nephrosclerosis / renal failure
  • cerebrovascular disease
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13
Q

What are the positive effects of intervention of hypertension?

A
  • every 10mmHg reduction in blood pressure it results 8n :

17% reduction for CHD

27% reduction for stroke

28% reduction for heart failure

13% reduction in all cause mortality

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14
Q

What is the equation for mean arterial blood pressure ?

A

Mean arterial blood pressure = cardiac output x total peripheral resistance

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15
Q

What regulates blood pressure in the short term ?

A

Baroreceptor reflex.

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16
Q

Where are barorecetoros found?

A

Carotid sinus

Aortic arch

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17
Q

How do baroreceptors act to quickly change the BP back to normal ?

A

1) alter autonomic inputs to the heart to change cardiac output
2) alter total peripheral resistance by affecting the sympathetic inputs to the blood vessels.

18
Q

If the arterial blood pressure is high , how the blood pressure returned back to normal ?

A
  1. Baroreceptors detect the changes in blood pressure as they detect stretch in the carotid sinus / aortic arch.
  2. Nerve endings of the baroreceptors will communicate information the medulla via firing an increase in the number of action potentials.
  3. The medulla would then activate the parasympathetic efferent nerves and inhibit the efferent sympathetic nerves. This would cause vasodilation of the blood vessels and a decrease in the heart rate.
19
Q

Why do baroreceptors not control sustained increased in blood pressure ?

A

Because the threshold for baroreceptor firing re sets.

20
Q

In medium or longer term control of blood pressure , what are the four neurohumoral pathways that control it ?

A
  1. Renin-angiotensin -aldosterone system
  2. Sympathetic nervous system
  3. Antidieurtic hormone
  4. Atrial natriuretic peptide ( ANP)
21
Q

What is renin?

A

It is released from granular cells of the juxtaglomerular apparatus ( JGA) which are found next to the glomerulus.

22
Q

What is renin release stimulated by?

A
  1. Reduced kidney perfusion ( reduced delivery of blood to kidneys) this is detected by baroreceptor in afferent arteriole.
  2. Reduced NACL delivery to the distal convoluted tubule,
  3. Sympathetic stimulation of the JGA in the kidneys
23
Q

Does renin work to increases or decrease blood pressure ?

A

Increase blood pressure

24
Q

Outline how renin works to increase blood pressure

A
  1. Angiotensinogen produced by liver is circulating in blood and is converted into angiotensin 1 by renin.
  2. Angiotensin 1 is then converted into angiotensin 11 by ‘ angiotensin converting enzyme -ACE’ in the lung epithelial cells.
  3. Angiotensin 11 acts on both angiotensin receptor 1 and 2 ( mainly 1).
  4. This causes vasoconstriction of arterioles. Kidneys to reabsorbed more sodium , so more water. Aldosterone release from adrenal cortex. Increased release of noradrenaline. Increases thirst sensation because it stimulates ADH release - this causes us to drink more.
25
Q

What is the effect of aldosterone on the kidney

A
  1. Aldosterone acts on principle cells of collecting ducts.

This causes :

  1. Stimulates reabsorption of Na+ into blood , therefore increased water absorption because there is an increased expression of Na+/K ATPase in basolateral wall of collecting ducts. And activation of ENaC ( epithelial sodium channels) & apical K+ channels.
26
Q

What else does angiotensin converting enzyme ( ACE) also break down ?

A

Bradykinin into peptide fragemts

Bradykinin is a vasodilator.

27
Q

How does the sympathetic nervous system help control blood pressure ?

A
  1. The sympathetic nervous system is stimulated by a decrease in the blood pressure .
  2. High levels of sympathetic stimulation results in decreased renal blood flow by causing vasoconstriction of the afferent arterioles. This decreases glomerular filtration rate which increases sodium retention and hence fluid retention raising BP.
  3. Activates apical Na/H exchanger and basolateral Na/K+ ATPase in the tubules to increase sodium rebabsorption.
  4. Stimulates renin release from the JGA cells to increase the RAAS activation.
28
Q

How does ADH control long term blood pressure ?

A
  1. ADH is released from the posterior pituitary gland in response to hypovolaaemia ( decreases volume of blood in the body) and high plasma osmolality.
  2. ADH increases water absorption by causing insertion of aquaporin channels in the collecting duct - this causes concentrated urine formation by increasing water reabsorption from the kidney.
  3. ADH also stimulates vasoconstriction of blood vessels to help raise BP.
29
Q

How does atrial natriuretic peptide (ANP) help control blood pressure ? A COUNTER REGULATORY SYSTEM

A
  • ANP is synthesised and stored in atrial myocytes which detect stretch in atria.
    2. ANP is released in response to stretch often caused by increased filling of the heart often caused by high BP.
    3. ANP causes increased secretion of Na+ and water to lower BP by inhibiting sodium reabsorption in kidney. Stimulating vasodilation of afferent arterioles to increase blood flow to kidneys and GFR.
30
Q

How to treat hypertension using a non pharmacological approach ?

A

Exercise

Diet

Reduced Na+ Intake

Reduced alcohol intake

31
Q

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

A
  • ACE inhibitors which prevent production of Ang11 from Ang1.
  • Ang 11 receptor antagonists
  • by blocking the action or production of Ang 11 it has vasodilator and dieuretic effects.
32
Q

People who take ACE inhibitors, what is a common side effect ?

A

An accumulation of bradykinin which often results in a troublesome dry cough as bradykinin is present in the lungs.

33
Q

How to treat hypertension ? - by providing vasodilator

A

1) L type ca channel blockers eg verapamil which reduce Ca entry to vascular smooth muscle cells. This would relax the vascular smooth muscle.
2) a1 receptor blockers get doxazosin which can reduce sympathetic tone - allowing relaxation of vascular smooth muscle.

34
Q

How to treat hypertension using diuretics?

A

1) thiazides dietetics which inhibit Na/Cl contransporter on apical membrane of cells in distal tubule this prevents reabsorption of Na+ into the cells.
2) other dieuretics involve aldosterone antagonists. ( but this is not the first line of choice )

35
Q

How to treat hypertension with beta blockers ?

A
  • these are less commonly used.
  • blocking b1 receptors in the heart will reduce the effects sympathetic output so would reduce heart rate and contractility.
  • this is not used in hypertension alone.
36
Q

What are the three common causes for secondary hypertension?

A

1) renovawcular disease
2) renal parenchymal disease
3) adrenal causes eg conns syndrome and Cushing syndrome.

37
Q

What is conns syndrome and how does this cause hypertension?

A

Too much aldosterone is produced from an adenoma.

38
Q

What is Cushing syndrome and how does this cause hypertension ?

A

Excess secretion of the g,uctocorticoid cortisol

39
Q

How can tumour of the adrenal medulla eg a phaeochromocytoma lead to hypertension?

A

Excess secretion of the catecholamines which leads to increase section of adrenaline and noradrenaline which stimulates the sympathetic nervous system.

40
Q

How can renovascular disease lead to hypertension?

A

1) occlusion of the renal artery eg renal artery stenosis causes a fall in perfusion in that kidney.
2. Baroreceptors in the afferent arteriole detect that the blood Pressure in the kidneys are low.
3. This goes off to stimulate the sympathetic nervous system which causes vasoconstriction of arterioles , decreases GFR , decreases Na+ excretion.
4. Stimulation of the sympathetic nervous system also goes off to stimulate renin release from juxtaglomerular apparatus ( JGA).
5. This leads to increased Ang 11 levels , leading to increased aldosterone levels , increased Na+ absorption.

41
Q

How do prostaglandins effect blood pressure ?

A
  • they act as vasodilators
  • they can enhance glomerular filtration rate and reduce Na+ reabsorption
  • they act as a buffer system to excessive vasoconstriction produced by the RAA system.
  • important when the levels of Ang 11 are very high
42
Q

What is the role of dopamine in regulation of blood pressure ?

A
  • dopamine is formed in the kidney
  • dopamine receptors are present on renal blood vessels , PCT
  • dopamine causes vasodilation and increases renal blood flow.
  • DA reduces reabsorption of NACL.

Cardiovascular (18 decks)

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