Control of blood water potential Flashcards
What is osmoregulation?
When the kidneys regulate the water potential of the blood so the body has just the right amount of water
What happens if the water potential of the blood is too low?
More water is reabsorbed by osmosis into the blood from the tubule of the nephrons.
This means the urine is more concentrated so less water is lost during excretion.
What happens if the water potential of the blood is too high?
Less water is reabsorbed by osmosis into the blood from the tubules of the nephrons. This means the urine is more dilute, so more water is lost during excretion.
Where does regulation of water take place?
Loop of Henle
DCT
Collecting duct
Where is the Loop of Henle located?
In the medulla of the kidneys
Name the 2 limbs the make up the Loop of Henle
Ascending
Descending
What do the limbs of the Loop of Henle control?
The movement of sodium ions so that the water can be reabsorbed by the blood
What happens as the top of the ascending limb?
Sodium ions are pumped out into the medulla using active transport
What happens as a result of the ascending limb being impermeable?
Water stays inside the tubule.
This created a lower water potential in the medulla as there is a high concentration of ions
Why does water move of the descending limb into the the medulla?
There is a lower water potential in the medulla than in the descending limb (osmosis)
What does the movement of water into the medulla result in?
Makes the filtrate move concentrated
What happens to the water in the medulla?
It is reabsorbed into the blood through the capillary network
What happens near the bottom of the ascending limb?
Sodium ions diffuse out into the medulla which further lowers the water potential in the medulla
What does water move out of by osmosis?
DCT
(and then reabsorbed into the blood)
What happens as a result of an increase ion concentration in the medulla?
A lowered water potential
What does a lower water potential mean?
It causes water to move out of the collecting duct by osmosis. The water is then reabsorbed into the blood through the capillary network
What controls the volume of water reabsorbed into the capillaries?
The changing permeability of the DCT and the collecting duct
What monitors the water potential of the blood?
Osmoreceptors
Where are osmoreceptors found?
In the hypothalamus
What happens when the water potential of the blood is low?
Water will move out of the osmoreceptor cells by osmosis
What happens when water moves out of the osmoreceptors?
Cells decrease in volume
This sends a signal to other cells in the hypothalamus which send a signal to the posterior pituitary gland.
What happens when the posterior pituitary gland receives a signal?
It releases a hormone called antidiuretic hormone (ADH) into the blood
What does ADH do?
Makes the walls of the DCT and collecting duct more permeable
What happens as result of the DCT and collecting duct being more permeable?
It means that more water is reabsorbed from these tubules into the medulla and into the blood by osmosis.
A small amount of concentrated urine is produced which means less water is lost from the body
