Lecture 4. Role of kidney regulating total body H2O Flashcards
Where is H2O reabsorbed? Which parts of the renal tubule?
Osmosis
Proximal Tubule: 65%
Descending limb of Henle
Distal tubule and collecting duct (fine control
Of ADH) (10%)
Ascending limb of henle is IMPERMEABLE to water
Of the filtrate. Less than 1% of H2O filtered is excreted
Where does ADH act on? What is its effect?
ADH increases the water permeability of the late distal tubule and collecting duct cells.
Increasing reabsorption of H2O and thus retaining water in the body.
What is the synthetic version of ADH/vasopressin?
Desmopressin
This will decreaSe urine volume, increase urine concentration because of reabsorption of water back into body.
Why is our urine concentrated in the morning?
In adults
There is increased secretion of ADH overnight. Less urine overnight, more concentrated urine in the morning.
What is the theory for nocturnal enuresis ?
Nocturnal enuresis is bed wetting
There is a developmental delay in overnight increased secretion of ADH.
What can you give to sb with nocturnal enuresis ?
Nasa spray of desmopressin
What are the symptoms of diabetes insipidus?
What are the two types of diabtest insipidus? What is the difference between them?
Diabetes insipidus
Something wrong regarding ADH
Symptoms:
- excessive thirst
- excretion of large amounts of dilute urine. Up to 25 Litres a day.
Two main types:
Central diabetes insipidus
Failure of the posterior pituitary to secrete ADH
Can be treated with desmopressin
Nephrogenic diabetes insipidus
Inability of the kidney to respond to ADH
- your osmoreceptors are responding properly. Normal secretion of ADH
BUT something wrong with the vasopressin Receptors
MAP Is monitored by….
Stretch-sensitive baroreceptors
ADH secretion and blood volume.
Name sequence of events from decreased blood volume.
- decreased blood volume
Therefore
-decreased Mean Arterial Pressure (MAP) - decreased firing rate of atrial and pulmonary stretch receptors
- decreased firing rate of arterial (aortic and carotid) baroreceptors.
- decreased neural impulses via cranial nerves to hypothalamic osmoreceptors.
- unrestrained massive synthesis and posterior pituitary release of ADH
Therefore increased water retention and decreased urinary excretion.
Where in the renal tubules does ADH act on?
We have Fine controL of ADH (anti-diuretic hormone or vasopressin)
In the DISTAL TUBULE AND COLLECTING DUCT ~9%
What is water diuresis?
an increase in urinary water output with little or no change in solute excretion.
Process of removinng excess pure water from the body –> correcting plasma hypoosmolarity.
Following drinking 1L of water we get diuresis of water.
Taking a water loading can be corrected within a couple of hours.
What are the intracellular mechanisms of ADH/vasopressin?
ADH released in blood stream. Peritubular capillaries.
Binds to V2, vasopressin receptor on the basolateral membrane.
Receptor is linked to an enzyme adenylate cyclase. ATP–> cAMP
cAMP activated intracellular protein kinases
That then phosphorylates these aquaporin channels and they get inserted into the LUMINAL membrane of the collecting duct cells. That then allows an increased in water reabsorption in this section of the kidney.
