Control Of Blood Pressure

Question 1

What is hypertension?

Answer 1

Sustained increase in blood pressure

Question 2

What is blood pressure measured in?

Answer 2

MmHg

Question 3

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

Answer 3

90/60mmHg and 120/80mmHg

Question 4

What causes hypertension? ( primary and secondary)

Answer 4

• 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

Question 5

Stage 1 hypertension values

Answer 5

Above 140/90 mmHg

Question 6

Stage 2 hypertension

Answer 6

160/100mmHg

Question 7

Severe hypertension

Answer 7

180/110

Question 8

Why is it important to treat hypertension?

Answer 8

• 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.

Question 9

What are a few diseases that result from hypertension?

Answer 9

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

Question 10

How can hypertension lead to heart failure ?

Answer 10

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

Question 11

How can hypertension lead to MI?

Answer 11

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.

Question 12

What does arterial damage result iN.

Answer 12

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

• nephrosclerosis / renal failure
• cerebrovascular disease

Question 13

What are the positive effects of intervention of hypertension?

Answer 13

• 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

Question 14

What is the equation for mean arterial blood pressure ?

Answer 14

Mean arterial blood pressure = cardiac output x total peripheral resistance

Question 15

What regulates blood pressure in the short term ?

Answer 15

Baroreceptor reflex.

Question 16

Where are barorecetoros found?

Answer 16

Carotid sinus

Aortic arch

Question 17

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

Answer 17

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.

Question 18

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

Answer 18

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.

Question 19

Why do baroreceptors not control sustained increased in blood pressure ?

Answer 19

Because the threshold for baroreceptor firing re sets.

Question 20

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

Answer 20

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

Question 21

What is renin?

Answer 21

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

Question 22

What is renin release stimulated by?

Answer 22

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

Question 23

Does renin work to increases or decrease blood pressure ?

Answer 23

Increase blood pressure

Question 24

Outline how renin works to increase blood pressure

Answer 24

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.

Question 25

What is the effect of aldosterone on the kidney

Answer 25

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.

Question 26

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

Answer 26

Bradykinin into peptide fragemts Bradykinin is a vasodilator.

Question 27

How does the sympathetic nervous system help control blood pressure ?

Answer 27

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.

Question 28

How does ADH control long term blood pressure ?

Answer 28

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.

Question 29

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

Answer 29

- 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.

Question 30

How to treat hypertension using a non pharmacological approach ?

Answer 30

Exercise Diet Reduced Na+ Intake Reduced alcohol intake

Question 31

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

Answer 31

- 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.

Question 32

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

Answer 32

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

Question 33

How to treat hypertension ? - by providing vasodilator

Answer 33

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.

Question 34

How to treat hypertension using diuretics?

Answer 34

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 )

Question 35

How to treat hypertension with beta blockers ?

Answer 35

- 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.

Question 36

What are the three common causes for secondary hypertension?

Answer 36

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

Question 37

What is conns syndrome and how does this cause hypertension?

Answer 37

Too much aldosterone is produced from an adenoma.

Question 38

What is Cushing syndrome and how does this cause hypertension ?

Answer 38

Excess secretion of the g,uctocorticoid cortisol

Question 39

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

Answer 39

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

Question 40

How can renovascular disease lead to hypertension?

Answer 40

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.

Question 41

How do prostaglandins effect blood pressure ?

Answer 41

- 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

Question 42

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

Answer 42

- 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.