Physiology blood pressure

1. Arterial Blood pressure

2. Long-term regulation of BP
1.
2.
Renal-Body fluid system
Renin-Angiotensin system

3. Renal-Body fluid system
•
(i)
•
Increase in Blood pressure:
Renal output of water increases →
Pressure
Diuresis
(ii) Renal output of sodium increases →
Pressure
Natriuresis
BP brought back to normal

4. Renin-Angiotensin system

7. Hypertension
•
•
Sustained elevation of Systemic Arterial
BP
Most commonly due to increase in
Peripheral resistance

8. Hypertension
•
•
•
•
Mean Arterial pressure ˃ 110 mmHg
This level of mean arterial pressure
occurs when:
Systolic BP ˃ 140 mmHg
Diastolic BP ˃ 90 mmHg

9. Types of Hypertension
1.
2.
Primary or Essential hypertension
Secondary hypertension

10. Primary or Essential
Hypertension
•
•
•
•
cause of Hypertension is unknown
About 90% of patients with Hypertension
Most common risk factor → Obesity
Treatable but not curable

11. Characteristics of Primary
Hypertension
1.
2.
3.
↑ peripheral resistance → most common
cause of hypertension
↑ cardiac output
↑ stimulation of sympathetic nerves

12. Characteristics of primary
Hypertension
4. ↑ levels of Angiotensin II & Aldosterone
5. ↓in Renal-pressure natriuresis
mechanism

13. Causes of Secondary
Hypertension
•
•
•
•
•
Renal artery stenosis, Parenchymal
disease
Coarctation of Aorta
Primary Aldosteronism, Cushing
syndrome, Pheochromocytoma
Estrogen treatment → “Pill hypertension”
Neurogenic hypertension

14. Complications of Hypertension
1.
2.
3.
4.
5.
Left ventricular hypertrophy
Coronary artery disease → MI
Cardiac failure
Stroke – cerebral infarct
Chronic kidney disease

15. Treatment of Hypertension
1.
2.
(i)
(ii)
(iii)
Exercise and weight loss – first step
Drugs
Drugs that block α-adrenergic receptors
Drugs that block β-adrenergic receptors
Drugs that inhibit ACE (Angiotensin-
converting enzyme)

16. Treatment of Hypertension
2. Drugs
(iv) Drugs that block Calcium channels →
causes relaxation of vascular smooth
muscle
(v) Drugs that causes Natriuresis or Diuresis
– Natriuretic or Diuretic drugs →
decreases tubular reabsorption of salt and
water

17. Hypotension
•
•
•
•
Sustained reduction in Arterial BP
Systolic BP → < 100 mmHg
Diastolic BP → < 60 mmHg
Sudden hypotension will cause loss of
consciousness called Fainting or Syncope

18. Causes of Hypotension
1.
2.
3.
↓ in cardiac output
↓ in peripheral resistance
↓ in blood volume

19. Postural Hypotension
• Prolonged standing → venous return
decreases → cardiac output decreases →
hypotension