Blood pressure and kidney

Question 1

Western diet

Answer 1

150-300 mmol sodium/day

Blood pressure: 120/80 mmHg

Question 2

Yanomamo Indian diet

Answer 2

10-20 mmol sodium/day

Blood pressure: 100/60 mmHg

Question 3

Whys is sodium levels linked to blood pressure

Answer 3

Na is the major electrolyte of the extracellular fluid volume (ECFV)
Interstitial fluid, plasma fluid, cerebrospinal fluid

Question 4

What do changes in Na cause?

Answer 4

• Changes in osmolarity
• ADH release
• H2O moves through ADH stimulated aquaporin channels in collecting duct
• Changes in ECFV (including blood)

Question 5

How does the CVS control Na levels?

Answer 5

Change in Na+ intake, change in ECFV - cardiac volume receptors, Baroreceptors, renal arterial pressure, leads to
Neuronal: Sym nervous system
Hormonal: RAAS, ANP
Haemodynamic: increase/decrease GFR, pressure natriuresis

Change renal Na+ ouput

Question 6

RAAS for Na conserve

Answer 6

ECFV, changes in blood pressure leads to release Renin to Angiotensin 1 (ACE) then makes Angiotensin 2 to:

• Release Aldosterone - increases Na reabsorption, decrease urine sodium
• Vascular smooth muscle cells - vasoconstriction - increases BP

Question 7

What factors stimulate renin release?

Answer 7

1. Decrease BP and Decrease BV and Decrease renal blood flow - afferent arteriole mechanoreceptors
2. Decrease Na levels at macula densa
3. Sympathetic nerve activation of B1 adrenoreceptors.
   Due to change in baroreceptors activity, and cardiac volume receptors

Question 8

Aldosterone

Answer 8

Steroid hormone synthesized in Zona glomerulosa of adrenal gland - released by the action of Ang 2

Question 9

Cardiac natriuretics

Answer 9

ANP (Atrial natriuretic peptide) and Brain natriuretic Peptide (BNP) found in specialized cardiac myocytes - released by increases cardiac filling pressure (Increase ECFV)

Question 10

Summary of effects on ANP

Answer 10

Renal - Natriuresis (increase Na excretion), Diuresis (increase H2O excretion)
Vasculature - Vasodilation by stimulation of PKG in VSMCs leads to decrease systemic BP, (Drugs)
Hormonal- Decrease Renin secretion, Decrease Aldosterone secretion

Question 11

Pressure Natriuresis

Answer 11

Increase renal Na+ excretion due to a rise in renal arterial pressure

Question 12

Hypertension

Answer 12

Systolic >140 mmHg and/or Diastolic > 90mmHg

Question 13

Are defects in renal Na+ handling involved?

Answer 13

Agents that decrease RAAS are frontline anti-hypertensive treatment e.g. ACE inhibitors, Ang 2 receptor blockers

Question 14

Conn’s syndrome

Answer 14

Increase ECFV, Decrease Plasma potassium, Decrease plasma renin activity