Blood pressure and the kidney Flashcards
Why does intracellular volume have little Na?
Intracellular volume has little Na – due to Na/K ATPase
What do changes in Na balance cause?
Changes in osmolarity and ADH release
What does ADH stimulate?
Changes in ECFV
H2O moves through ADH stimulated aquaporin channels in collecting duct
This causes changes in ECFV (including blood volume)
What does an increase in blood volume lead to?
Increasing blood volume leads to ventricular filling and increases SV (Starling’s law)
How does regulating Na levels regulate blood pressure?
Regulate Na levels - changes blood volume - long-term control of BP
How does the CVS control Na levels?
- Change in Na+ intake
- Change in ECFV
- Afferent pathways - cardiac volume receptors, baroreceptors, renal arterial pressure
- Efferent pathways:
Neuronal: Sym nervous system
Hormonal: RAAS and ANP
Haemodyanmaics: Increases/ decreases GFR, pressure natriuresis
- Change renal Na+ output
Describe the RAAS pathway
On image
What factors cause renin release?
- Decreasing BP BV - Descreases renal blood flow -
afferent arteriole mechanoreceptors - Decreasing Na levels at macula densa
- Sympathetic nerve activation
of β1 adrenoreceptors
Due to changes in baroreceptors activity, and cardiac volume receptors
What is the role of the muscular densa and Renin secreting Juxtaglomerular (granular) cells?
Region of contact between afferent arteriole and distal tubule of same nephron
Modified smooth muscle cells along the afferent arteriole
Where is aldosterone produced?
Aldosterone : steroid hormone synthesised in Zona glomerulosa of adrenal gland – released by action of Ang II
What channels does aldosterone act upon?
On image
Describe the role of aldosterone in the kidney
Where does it act?
What does it increase expression of?
What does this cause?
Role of aldosterone in kidney
Acts at steroid receptors inside cells
Increases expression of ENaC and Na/K pump
Increases Na reabsorption at
distal tubular sites
Results in Increases renal K excretion
Excess aldosterone leads to hypokalaemia
Where is Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) found and what do they cause?
Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) found in specialised cardiac myocytes - released by increases cardiac filling pressures ( increases ECFV)
What are the effects of ANP?
Renal
Natriuresis (Increases Na excretion)
Diuresis (Increasing H2O excretion)
Vasculature
Vasodilatation by stimulation of PKG in VSMCs - Increasing Systemic BP
(Drugs on VSM lecture)
Hormonal
Increases Renin secretion
Increases Aldosterone secretion
ANP system opposes RAAS
What does an increase in Na+ cause?
Increase renal Na+ excretion due to a rise in renal arterial pressure
