Sodium and Potassium balance Flashcards
(32 cards)
What is the effect of increasing dietary sodium
Increased osmolarity
Increased ECF volume
Increased blood volume and pressure
More water retained and weight increases
What is the effect of decreasing dietary sodium
Decreased osmolarity
Decreased ECF volume
Decreased blood volume and pressure
What is the relationship between GFR and sodium reabsorption
As GFR increases, sodium reabsorption increases (more fluid going in)
What substance decreases sodium reabsorption in the kidneys and where does it act
Atrial naturietic peptide
Efferent arteriole, proximal convoluted tubule, juxtaglomerulus apparatus and collecting duct
Which factors increase sodium reabsorption
Increased sympathetic activity
Angiotensin II
Low tubular sodium sensed by the juxtaglomerulus apparatus
Aldosterone
What does increased sympathetic activity affect
Afferent arteriole
Glomerular filtration rate (-)
Proximal convoluted tubule
Juxtaglomerulus
Draw a diagram to show how increased sympathetic activity, angiotensin II, low tubule sodium, aldosterone and atrial naturietic peptide affect reabsorption
diagram
Describe the RAAS
- Angiotensinogen from the liver
- Low osmolarity of cells at the JGA causes water to leave and the cells shrink
- Shrinking cells produce NO and PG2
- JGA releases renin
- renin converts angiotensinogen to angiotensin I
- ACE converts angiotensin I to angiotensin II (lungs with a large endothelial surface)
- aldosterone release from the zona glomerulosa of the adrenal gland
What are the effects of angiotensin II
Aldosterone synthesis in the adrenal gland
Increased sodium uptake in the PT, therefore increased water reabsorption
Increased extracellular fluid
Increased vasoconstriction
Increased blood pressure
Describe aldosterone
Steroid hormone
Released from the adrenal cortex in response to angiotensin II, decrease in blood pressure and decrease in osmolarity in ultrafiltrate
What does aldosterone do
Works on principal cells
Increases sodium reabsorption
Increases potassium secretion
Increases hydrogen ions= secretion
What is the effect of excess aldosterone
Hypokalaemic alkalosis
How does aldosterone work
- Binding of aldosterone
- Heat shock proteins released
- Receptors dimerise
- Travels to the nucleus and alters transcription
- Induces expression of sodium channels in the apical collecting duct membrane
- Induces formation of Na-K ATPase pumps via transcription
What is hypoaldosteronism
Reabsorption of sodium in the distal nephron is reduced
Increased urinary loss of sodium
ECF volume falls
Increased renin, angiotensin II and ADH
What are the symptoms of hypoaldosteronism
dizziness
Low blood pressure
Salt cravings
Palpitation
What is hyperaldosteronism
Reabsorption of sodium in the distal nephron is increased
Reduced urinary sodium loss
ECF volume increases
Reduced renin, angiotensin II and ADH
What are the symptoms of hyperaldosteronism
High blood pressure
Muscle weakness
Polyuria
Thirst
What is Liddle’s syndrome
Inherited disease of high blood pressure
Mutation in the aldosterone activated sodium channel so the channel is always active
Sodium retention and hypertension
Which baroreceptors come into contact with low pressure blood
Atria
Right ventricle
Pulmonary vasculature
Which baroreceptors come into contact with high pressure blood
Carotid sinus
Aortic arch
Juxtaglomerular apparatus
What is the response when there is low pressure at the high pressure baroreceptors
- Signal through afferent fibres to the brainstem
- Sympathetic activity
- ADH increased
- JGA cells release renin
What is the response when there is a pressure change at the low pressure baroreceptors
Low pressure
- Signal sent through afferent fibres to the brainstem
- Sympathetic activity and ADH increased
High pressure
- atrial stretch
- ANP, BNP released
What is ANP and what does it do
atrial natriuretic peptide
Small peptide made in the atria which is released in response to stretch
Vasodilation
Inhibition of sodium reabsorption
Inhibits renin and aldosterone release
Reduce blood pressure
How do carbonic anhydrase inhibitors work
Inhibits carbonic anhydrase to reduce sodium reabsorption and decreases urinary acidity
Protons are not liberated from H2CO3 and therefore are note exchanged with Na+
