L10-Osmoregulation Flashcards
Where is osmolality detected in order to determine when to release ADH? why is this an appropriate place?
It is detected anterloventeral third ventricle region of the brain (AV3V). This is an appropriate location as the blood brain barrier is incomplete.
How is ADH synthesised and released?
It is synthesised as a prohormone in the hypothamamus and is then cleaved to the hormone as it moves to the pituitary where it is released.
What is the half life of ADH?
Only around 10 minutes
What are the two ADH receptors and what do they do?
V1 receptors are mainly on smooth muscle cells of veins and cause constriction.
V2 receptors are on the collecting ducts of the kidneys and cause increased AQN2 channels in the membrane.
What effect does oxytocin have?
It triggers the milk let down reflex for breast feeding
It is an agonist at V1 and V2 receptors
It commonly triggers thirst
What is the maximum concentration our kidneys can concentrate our urine to?
1400mOsm
What is the maximum urine daily production rate?
25L
Why does drinking sea water of 2000mOsm cause dehydration?
The kidney can only concentrate to a maximum of 1400mOsm so to clear the salt it requires 2000/1400=1.4L of water
What are the dominant osmolytes that are ingested?
Carbohydrates, fat and proteins
What are the fates of carbohydrates and proteins post absorption?
Carbohydrates are mostly converted to simple sugars and transported into cells so do not massively effect osmolality.
Similarly proteins are broken down to amino acids which are taken up by cells so osmolality only changes small amounts.
Which has a higher renal clearance sodium or potassium ions?
Potassium
What effect does high glucose levels in diabetics have?
It can change the osmolality so causes a large thirst drive. If not sufficient then the individual can become hypernatraemic and suffer seizures and altered mental state.
Why did intranasal delivery of an ADH substitute cause nasal necrosis?
The V1 receptors caused vasoconstriction
What does osmoregulation change?
It changes the body water volume as when the osmolality changes then the body doesnt know if this is due to a change in volume or a change in the solute. This means it corrects by changing the volume and then it is the job of volume regulation to restore normal volume.
