US Lecture 6 - Sodium and Potassium Balance Flashcards
What is the main component of the ECF?
Sodium
What happens if you do a high sodium diet?
You will gain weight to try to balance the osmolarity but a decrease in sodium, reduces your weight
What are the effects of increasing sodium levels?
Increases osmolarity so the body increases ECF volume to reduce the osmolarity which causes an increase in blood volume and pressure
What are the effects of decreasing sodium levels?
Decreases osmolarity so the body decreases ECF to increase the osmolarity which causes a decrease in blood volume and pressure
Where is most sodium reabsorbed?
65% in the proximal convoluted tubule. 25% in ascending LoH, 8% in distal CT and 2% in CD
What happens if the GFR is increased/decreased to the reabsorption of sodium in the kidney?
As it is under relatively constant conditions, if GFR increases, so will Na reabsorption and vice versa
How is more Na reabsorbed from the body?
Reduce the amount of Na being filtered by -> reducing GFR
How is GFR reduced to reduce Na filtration into kidneys?
Arterioles (aff/efferent) are constricted - afferent more - which lowers the pressure so less filtrate goes through
What other ways of reabsorbing sodium is there?
The JGA stimulates the release of AngII, which acts of PCT to reabsorb more sodium. Also, aldosterone stimulates DCT and CT to reabsorb more Na If a low tubular Na is detected by the JGA, this stimmulates the release of AngII
How is sodium reabsorption decreased?
Atrial neturietic peptide -> dilates blood cells, reduces Na uptake in PCT/DCT/CD and reduces the stimulus on the JGA
What are the effects of sodium on the distal nephron?
Changes detected by JGA, which releases renin which stimulates cells in the liver to produce Ang > Ang I > Ang II
What stimulates and inhibits renin production?
Inhibits: increased BP and volume and decreased sympathetic stimulus Stimulates: decreased BP and volume and increased sympathetic stimulus
What are the effects of Ang II?
What is aldosterone?
Steroid hormone, synthesised and released from adrenal cortex in response to AngII, decrease in BP (baroreceptors) and decreased osmolarity of ultrafiltrate
What does aldosterone do?
Stimulates increased: Na reabsorption, K secretion and H+ secretion
What does excess aldosterone lead to?
Hypokalaemic alkalosis
How does aldosterone work?
Moves into cell and binds to a receptor inside the cell, inducing expression of apical Na channel of the collecting duct and promotes its activity. Also induces formation of Na-K-ATPase pumps
What are the diseases of aldosterone secretion?
Hypoaldosteronism, hyperaldosteronism and Liddle’s syndrome
What is hypoaldosteronism?
Reabsorption of sodium in the distal nephron reduced, increased urinary loss of sodium, ECF volume falls and increases renin, Ang II and ADH.
What are the symptoms of hypoaldosteronism?
Dizziness, low BP, salt craving and palpitations
What is hyperaldosteronism?
Reabsorption of Na at distal nephron is increased, reduced urinary loss of sodium, ECF volume increases, reduced renin, Ang II and ADH Increased ANP and BNP