Hypertension And The Sympathetic NS

Question 1

What is blood pressure regulated by?

Answer 1

1. Sympathetic nervous system: sympathetic release of noradrenaline causes:
   
   • heart (beta1): positive chonotropy (tachycardia, SA node) and positive inotropy (ventricles) - increased cardiac output.
   • arterioles in peripheral vasculature (alpha1): vasoconstriction - increased peripheral resistance.
2. Renin-angiotensin-aldosterol system
   
   • kidney: renin release to decrease Na+/water loss.

Question 2

What is normal blood pressure?

Answer 2

120/80 mmHg

Question 3

What is hypertension and what are the 2 types?

Answer 3

Hypertension = increase in BP to >140/90 mmHg. 2 types:

• primary/essential (95%) - no specific cause
• secondary - associated with other pathology, normally renal disease (or in rare cases Conn’s or phaeochromocytoma)

Question 4

What are the target sites for drug action to control abnormally elevated BP?

Answer 4

• Heart (beta1 adrenoreceptors)
• Arteriolar smooth muscle (alpha1 adrenoreceptors)
• Kidney (RAAS)
• CNS - determines BP set point

Question 5

Suggest possible therapeutic drugs in hypertension.

Answer 5

1. Alpha-blockers: vasodilator - antagonise alpha1-adrenoreceptors in vasculature.
2. Beta-blockers: decrease cardiac output (by decreasing rate and force of heart)
   decrease renin production - increase kidney secretion of water as less aldosterone is produced
3. Calcium channel blockers: smooth muscle vasodilator - prevent release of internal calcium stores into cell cytosol - cardiac muscle can’t respond to calcium ion signal
4. Angiotensin converting enzyme inhibitors (ACEi): inhibit production of angiotensin II.
5. Angiotensin II inhibitors (ARBs): inhibit action of angiotensin II.
6. Diuretics: increase Na+ and water loss from kidneys.

Question 6

Which of the therapeutic drugs used to treat hypertension should not be used in >55 and those of African/Caribbean origin and why?

Answer 6

• Angiotensin converting enzyme inhibitors

- As they normally produce less renin

Question 7

What are the main side effects of alpha-adrenoreceptor antagonists in treating hypertension?

Answer 7

• postural hypotension
• impotence
• diarrhoea (due to increased gastrointestinal motility)
• arrhythmias (very rare)

Question 8

What are the main side effects of beta-adrenoreceptor antagonists in treating hypertension?

Answer 8

• bronchoconstriction in asthmatics and blocking of anti-asthmatic beta-adrenoreceptor agonist action.
• cardiac failure in patients with pre-existing heart disease who may rely on sympathetic drive to maintain cardiac output.
• bradycardia
• physical fatigue due to decrease CO and decreased beta-adrenoR-mediated increase in skeletal muscle flow during exercise.
• decreased hypoglycaemia awareness due to sweating, tremors, etc.
• impotence

Question 9

Why might there be poor compliance hypertension drugs?

Answer 9

Hypertension is usually asymptomatic whereas treatments all have side effects.