Tubular function 4 Flashcards
What are the clinical manifestations of excess sodium
Weight gain
Oedema formatin
Hypertension
Nocturia
What are the clinical manifestations of deficit of sodium
weight loss
changes in skin turgor
Fainting
Orthostatic hypotension
What are the 2 major influences on Na+ excretion
GFR
Tubular reabsorption of Na+ (collecting duct=fine control)
What are the effector mechanisms influencing renal Na+ transport
Renin-angiotensin-aldosterone system
Sympathetic nervous system
Atrial natriuretic peptide
Natruiretic factors
ADH/vasopressin
What effector mechanisms have a positive influence on renal Na+ transport
RAAs
Sympathetic nervous system
How does the RAAs influence renal Na+ transport
Angiotensin 2 and aldosterone increase proximal tubule Na+ reabsorption
Aldosterone increases late distal / CCD Na+ reabsorption
How does the SNS affect renal Na+ transport
Noradrenaline increases proximal Na+ reabsorption
Activates RAA which increases Na+ reabsorption
Decreases GFR which decreases Na+ excretion
Which effector mechanisms decrease renal Na+ transport
Atrial natriuretic peptide (ANP)
Natriuretic factors
How does ANP affect renal NA+ transport
Increases GFR (vasodilation- increases Na+ excretion)
Decreases proximal tubule and collecting duct Na+ reabsorption
Inhibits aldosterone and renin release
How do Natriuretic factors affect renal Na+ transport
Decrease proximal Na+ reabsorption
Inhibit renin release which increases Na+ excretion
Inhibits RAA
Effect on prostanoids which change GFR
Where is renin released
Juxtaglomerular apparatus - (made up of macula densa and granular cells)
How does the macula densa mechanism stimulate release of renin from granular cells
macula densa mechanism- decrease of sodium delivery to distal tubule (e.g. when there’s a low plasma sodium level or low blood pressure or low extracellular fluid volume)
-less salt is transported by Na-Cl co transporter by macula densa and when there’s a decrease in deliver, that triggers the release of renin
How does the renal baroreceptor mechanism affect renin release
fall in renal perfusion pressure (bp fall or extracellular fluid fall) triggers renin release
or when catecholamine levels released (compensatory response of SNS to a fall in blood pressure or EX fluid volume) – act on beta are
How does the catecholamine mechanism affect renin release
Catecholamine levels are increased when there’s a compensatory response of SNS to a fall in blood pressure or extracellular fluid volume
It then acts on beta adrenoceptors on macula densa cells which then stimulate release of renin
What are the components of the RAAS
Renin released from granular cells of jga
Increases angiotensinogen from liver which gets turned to angiotensin 1 by renin
This gets turned to angiotensin 2 by ACE
Stimulates aldosterone release from adrenal cortex which increases distal Na+ uptake
