Solute Homeostasis

Question 1

What percentage of sodium filtered by the kidneys is reabsorbed?

Answer 1

99%

Question 2

What would be done to counteract an increase in ECF sodium concentration?

Answer 2

ADH secretion and water retention

Question 3

What would be done to counteract a decrease in ECF sodium concentration?

Answer 3

Water excretion

Question 4

What stimulates release of renin?

Answer 4

Decrease in blood pressure which decreases the stimulation of stretch receptors
Sympathetic stimulation to granular cells
Decrease in salt delivery to macula densa which results in paracrine release

Question 5

Describe the renin angiotensin aldosterone pathway

Answer 5

Renin stimulates conversion of angiotensinogen into angiotensin I
Angiotensin I is converted into angiotensin II
Angiotensin II stimulates aldosterone release

Question 6

What are the systemic effects of the RAA system?

Answer 6

Vasoconstriction to increase blood pressure
ADH release
Increased thirst and salt appetite

Question 7

What are the renal effects of the RAA system?

Answer 7

Decreased glomerular filtration

Increased tubular reabsorption

Question 8

What causes decreased glomerular filtration in response to RAA?

Answer 8

Efferent vasoconstriction

Mesangial cell contraction decreases filtration area

Question 9

What causes increased tubular reabsorption of sodium in response to RAA?

Answer 9

Increase Na/K/ATPase activity

Question 10

What stimulates release of aldosterone?

Answer 10

Angiotensin II

Hyperkalaemia

Question 11

What is the role of aldosterone?

Answer 11

Increased transcription of ENaC and ROMK channels to increase sodium reabsorption and decrease potassium secretion

Question 12

What is the role of serum glucocorticoid kinase? How is it stimulated?

Answer 12

Stimulated by aldosterone
Increases ENaC and ROMK activity
Increases sodium reabsorption
Decreases potassium secretion
Increases hydrogen ion secretion in collecting duct
Increases sodium reabsorption in gut and sweat glands

Question 13

Where is atrial natriuretic peptide released from?

Answer 13

Right atrium

Question 14

What stimulates atrial natriuretic peptide release?

Answer 14

Increased pressure in right atrium

Question 15

What are the effects of atrial natriuretic peptide?

Answer 15

Closure of ENaC channels
Inhibition of Na/K/ATPase
Inhibition of aldosterone secretion
Inhibition of renin secretion
Afferent arteriole vasodilation
Inhibits Na/H exchanger

Question 16

How does potassium transport differ between the PCT & loop and DCT & duct?

Answer 16

Potassium transport in the PCT and loop is constitutive

It can be altered in the DCT and duct

Question 17

What causes hypokalaemia?

Answer 17

Diarrhoea
Vomiting
Hyperinsulinemia
Fluid replacement without potassium

Question 18

What causer hyperkalaemia?

Answer 18

Acidosis
Renal failure
Insulin deficit
Tissue death

Question 19

What are the symptoms of hypokalaemia?

Answer 19

Muscle weakness
Dysrhythmia
Polyuria
Thirst

Question 20

What are the symptoms of hyperkalaemia?

Answer 20

Muscle weakness

Dysrhythmia

Question 21

What causes muscle weakness in hyperkalaemia?

Answer 21

The membrane has a higher resting potential which decreases the threshold, so the cell cannot return to true rest

Question 22

What causes muscle weakness in hypokalemia?

Answer 22

A lower resting potential increases the threshold

Question 23

How is potassium concentration regulated?

Answer 23

High potassium stimulates secretion of aldosterone which decreases potassium secretion

Question 24

How does increased tubular flow increase potassium excretion?

Answer 24

Increase flow bends the cilia which allows a calcium influx by PKD1/2
Calcium influx activates ROMK channels so more potassium is secreted

Question 25

How are pH and potassium levels linked?

Answer 25

Proton secretion in intercalated cells is tied to potassium reabsorption

Question 26

What hormones regulate calcium and phosphate levels?

Answer 26

Parathyroid hormone
Calcitonin
Vitamin D

Question 27

What stimulates release of parathyroid hormone?

Answer 27

Increasing serum phosphate

Decreasing serum calcium

Question 28

What stimulates release of calcitonin?

Answer 28

Increasing serum calcium

Question 29

What is the role of parathyroid hormone?

Answer 29

Stimulates vitamin D synthesis
Increases calcium resorption from bone
Increases renal calcium reabsorption by increasing TRPV5/6 activity
Decreases renal phosphate reabsorption by decreasing abundance of NPT2

Question 30

What is the benefit of increasing renal calcium reabsorption while decreasing renal phosphate reabsorption?

Answer 30

Calcium phosphate is near the solubility limit, therefore if your add more calcium into the tubule then phosphate should be removed to prevent precipitation

Question 31

What is the role of calcitonin?

Answer 31

Decreases renal phosphate reabsorption
Increases bone formation
Inhibits calcium resorption from bone

Question 32

What is the role of vitamin D?

Answer 32

Increases renal calcium reabsorption by increasing TRPV5/6 abundance
Increases calbindin abundance
Decreases renal phosphate reabsorption

Question 33

Describe calcium reabsorption in the collecting duct

Answer 33

Calcium diffuses into the cell from the tubule via TRPV5/6 channels
Some calcium is absorbed by calbindin
Calcium is then transported out of the cell by PMCa ATPase and Sodium Calcium exchanger

Question 34

Describe potassium reabsorption in the proximal tubule

Answer 34

Na/K/ATPase sets up a sodium gradient
Phosphate is brought into the cell via cotransport with sodium
Phosphate is then exchanged on the basolateral membrane by an anion exchanger

Question 35

How is magnesium reabsorbed?

Answer 35

Mostly paracellularly