Flashcards in Physiology (6-8) Deck (96)
What is the tonicity of the tubular fluid entering the DCT compared to blood?
What is the collecting duct bathed in?
Progressively increasing [ISF]:
- 300 -> 1200mosmol/L
What percentage of filtered ions are reabsorbed before the DCT?
What is the residual load of NaCl that reaches the DCT?
Why is the residual load of NaCl in the DCT important?
What effect does ADH have on the regulation of water and ion balance?
Increases water reabsorption
What effect does Aldosterone have on the regulation of water and ion balance?
Increases Na+ reabsorption
Increases H+ and K+ excretion
What effect does Atrial Natriuretic hormone have on the regulation of water and ion balance?
Reduces Na+ reabsorption
What effect does PTH have on the regulation of water and ion balance?
Increases calcium reabsorption
Decreases phosphate reabsorption
What does the DCT have a low permeability to?
What happens in the early segment of the DCT?
NaCl reabsorption via the Triple-transporter
Which of the following does not happen in the late segment of the DCT:
- Calcium reabsorption
- H+ secretion
- Na+ reabsorption
- K+ reabsorption
- Phosphate secretion
What is the early collecting duct similar to?
What is the permeability of the late collecting duct?
Low ion permeability
High water permeability
Where is ADH (an octopeptide) synthesised and from what?
Supraoptic nuclei and Paraventricular nuclei in the hypothalamus
Where is ADH stored?
In granules in the posterior pituitary
What is the approximate half life of ADH in the plasma?
How does ADH increase water reabsorption?
1. Binds to an Arginine Vasopressin Receptor 2 (V2)
2. ATP -> cAMP
3. cAMP causes increased transcription and insertion of aquaporins in the lumenal/apical membrane
In high [ADH]p, what is urine like?
Hypertonic (Up to 1400mosmol/L)
In low [ADH]p, what is urine like?
Hypotonic urine (
What is the dominant factor controling thirst and ADH secretion?
Increased osmolarity activating hypothalamic osmoreceptors
When are left atrial volume receptors important in water balance?
In large plasma volume or BP changes
What causes left atrial volume receptors to encourage ADH release?
Very low plasma volume
Hugh drop in BP
Apart from increasing water reabsorption, how else does ADH increase BP?
Causes peripheral vasoconstriction -> BP rises
Where is aldosterone secreted from?
When is aldosterone secreted?
In response to:
- Increased [K+]p
- Decreased [Na+]p
Activation of RAAS
If aldosterone is absent, how much K+ is present in the urine?
How does decreased [Na+]p result in aldosterone secretion?
Indirectly via the juxtaglomerular apparatus
Where is renin produced and what does it do?
- Converts Angiotensinogen -> Angiotensin I