Skip to main content
Like
Create new Glog
previous
next
Email share
43 views | 0 likes | 0 reposts
Sodium in Fluid and Electrolyte Balance Changes in plasma sodium levels affect: Plasma volume, blood pressure ICF and interstitial fluid volumes Renal acid-base control mechanisms are coupled to sodium ion transport
Regulation of Sodium Balance Sodium reabsorption 65% of sodium in filtrate is reabsorbed in the proximal tubules 25% is reclaimed in the loops of Henle When aldosterone levels are high, all remaining Na+ is actively reabsorbed Water follows sodium if tubule permeability has been increased with ADH
Regulation of Sodium Balance The renin-angiotensin mechanism triggers the release of aldosterone This is mediated by the juxtaglomerular apparatus, which releases renin in response to: Sympathetic nervous system stimulation Decreased filtrate osmolality Decreased stretch (due to decreased blood pressure) Renin catalyzes the production of angiotensin II, which prompts aldosterone release
Regulation of Sodium Balance Adrenal cortical cells are directly stimulated to release aldosterone by elevated K+ levels in the ECF Aldosterone brings about its effects (diminished urine output and increased blood volume) slowly
Cardiovascular System: Baroceptors Baroreceptors alert the brain of increases in blood volume (hence increased blood pressure) Sympathetic nervous system impulses to the kidneys decline Afferent arterioles dilate Glomerular filtration rate rises Sodium and water output increase
Barorecptors This phenomenon, called pressure diuresis, decreases blood pressure Drops in systemic blood pressure lead to opposite actions and systemic blood pressure increases Since sodium ion concentration determines fluid volume, baroreceptors can be viewed as “sodium receptors”
Atrial Natriuretic Peptide Reduces blood pressure and blood volume by inhibiting: Events that promote vasoconstriction Na+ and water retention Is released in the heart atria as a response to stretch (elevated blood pressure) Has potent diuretic and natriuretic effects Promotes excretion of sodium and water Inhibits angiotensin II production
