6. Control Of BP And Hypertension

Question 1

How do you calculate mean arterial BP?

Answer 1

Cardiac output * total peripheral resistance

Question 2

How do you calculate cardiac output?

Answer 2

Stroke volume * heart rate

Question 3

What is responsible for short term regulation of blood pressure?

Answer 3

Baroreceptor reflex

Question 4

What are the 4 neurohumoral pathways which control BP long term

Answer 4

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

Question 5

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

Answer 5

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

Question 6

What cells is renin released from?

Answer 6

Granular cells of juxtaglomerular apparatus (JGA) in the kidney

Question 7

What 3 factors stimulate renin release?

Answer 7

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)

Question 8

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

Answer 8

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

Question 9

What 3 affects does angiotensin II have to increase BP

Answer 9

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

Question 10

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

Answer 10

AT1 and AT2
Main actions via AT1
GCPR

Question 11

Give 3 sites of angiotensin II receptors, and their action

Answer 11

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

Question 12

What cells does aldosterone mainly act on?

Answer 12

Principle cells of collecting ducts

Question 13

What 3 things does aldosterone stimulate/activate?

Answer 13

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

Question 14

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

Answer 14

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

Question 15

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

Answer 15

ACE inhibitors

Ang II receptor antagonists

Question 16

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

Answer 16

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.

Question 17

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

Answer 17

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

Question 18

What 2 things stimulate ADH release?

Answer 18

Increases in plasma osmolarity

Severe hypovolaemia

Question 19

What does atrial natriuretic peptide promote?

Answer 19

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

Question 20

Where is atrial natriuretic peptide synthesised and stored?

Answer 20

Atrial myocytes

Question 21

When is atrial natriuretic peptide released?

Answer 21

From atrial cells in response to stretch

Question 22

Is atrial natriuretic peptide released to increase or decrease BP?

Answer 22

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

Question 23

What do prostaglandins do?

Answer 23

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.

Question 24

Where is dopamine formed and what is it formed from?

Answer 24

In the kidney, from circulating L-DOPA

Question 25

Where are dopamine receptors present?

Answer 25

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

Question 26

What does dopamine cause to happen?

Answer 26

Vasodilation in kidneys | Reduced reabsorption of NaCL

Question 27

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

Answer 27

Sustained increase in BP | Stage I, II or severe

Question 28

What is primary hypertension?

Answer 28

Cause is unknown

Question 29

What is secondary hypertension?

Answer 29

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

Question 30

What is renovascular disease?

Answer 30

Occlusion of the renal artery (stenosis)

Question 31

How does renovascular disease lead to secondary hypertension?

Answer 31

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

Question 32

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

Answer 32

Early stage - loss of vasodilator substances. | Later stage - Na+ and water retention due to inadequate glomerular filtration (volume dependant hypertension).

Question 33

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

Answer 33

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

Question 34

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

Answer 34

LV hypertrophy - heart failure | Increased myocardial oxygen demand - myocardial ischaemia and MI

Question 35

Hypertension leads to arterial damage. HWat does this cause?

Answer 35

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

Question 36

What target organs should be assessed in hypertension?

Answer 36

Brain, eyes, heart, kidneys, arteries

Question 37

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

Answer 37

Equation for mean arterial BP

Question 38

Give 3 non-pharmacological approaches for treating hypertension

Answer 38

Exercise Reduced Na+ intake Reduced alcohol intake Diet

Question 39

What could limit the effectiveness of antihypertensive therapy?

Answer 39

Failure to implement lifestyle changes

Question 40

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

Answer 40

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.

Question 41

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

Answer 41

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

Question 42

What do beta blockers do?

Answer 42

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