L10: Osmoregulation Flashcards
What is ADH also known as
Vasopressin
Where is ADH Synthesised
In the hypothalamus
Where is ADH stored and released from
The posterior pituitary gland
Where is osmolality in the brain detected
Anterioventral third ventricle (AV3)
What does the AV3 region contain
Neurones that synthesis ADH
Which protein is ADH released with
Neurophysin
What is the half life of ADH
Short
Which receptors does ADH act on in the kidneys
V2 receptors
What type of receptors are V2 receptors
GPCRs with Gi attached
What happens when ADH binds to V2 receptors
Gi stimulates adenylyl cyclase
Adenyly cyclase produces CAMP
CAMP increases the synthesis of AQP2 in the collecting duct
CAMP activates PKA which causes the insertion of AQP2 into the apical membrane
What receptors do ADH bind to in the veins
V1 receptors
What does ADH/vasopressin cause in the veins
Vasoconstriction
What is the structure of Aquporins
4 subunits
Each subunit has a pore for water= 4 pores
What other hormone does the posterior pituitary gland release
Oxytocin
What is the role of oxytocin
Trigger milk production
Which receptors do oxytocin act on
V1 and V2 receptors
What does less water intake do to the osmolality
Increase it
When do we get a decreased osmolality
When we have a great intake of water
What happens to ADH levels when there is a decreased osmolality
ADH levels are suppressed
With max ADH what is the volume of urine we produce a day
300-400ml
When there is no ADH what is the volume of urine we produce a day
25 litres
What is the concentration of urine like when there is max ADH
Concentrated
What is the concentration of urine like when there is no ADH
Dilute
What is the max urine osmolality we can produce
1400 mosmkg-1
Why can we not drink sea water
The osmolality of sea water is high and to get rid of this high osmolality we lose water
Which 2 ions area big impact on osmolality
Sodium
Potassium
Why is sodium important in osmolality
Sodium stays in the extracellular space for a long time and does not get taken up into cells
Therefore sodium is the main contributor to osmolality because it is not taken up into cells
Does potassium stay in the body more or it is secreted
Mostly secreted
In diabetes mellitus why do patients drink lots of water
An increase in glucose increases osmolality
This increased osmolality induces thirst and patient drink more
Why do patients with diabetes mellitus have confusion
When they are thirsty due to an increase in glucose
ADH is released
This reabsorbed water and sodium concentration falls leading to hyponatremia
This results in seizures and confusion
When does osmoregulation regulate the concentration
When we change the solute content
When does osmoregulation correct the volume change
When we change the water content of the body
Overall what are the roles of osmoregulation i.e ADH
Correct body volume
Correct solute content
