3.6.4.3 control of blood water potential Flashcards
What are the 4 stages of water reabsorption by the kidneys
- Ultrafiltration by the glomerulus
- Selective reabsorption by the proximal convoluted tubule
- Loop of Henle , where in the ascending limb sodium ions are actively transported out and in the descending limb water moves out by osmosis and into capillaries.
- Collecting duct, where water moves out into the blood
Where are osmoreceptors?
In the hypothalamus
Where specifically is ADH secreted from?
The posterior pituitary gland
What does ADH stand for?
Antidiuretic hormone
Describe and explain ultrafiltration and selective reabsorption, including where they occur.
What is osmoregulation?
Osmoregulation is a key part ofhomeostasis
Specialisedsensory neurones, known asosmoreceptors, monitor the water potential of the blood (these osmoreceptors are found in an area of the brain known as thehypothalamus)
If the osmoreceptors detect adecreasein the water potential of theblood, nerve impulses are sent along these sensory neurones to theposterior pituitary gland(another part of the brain just below the hypothalamus)
These nerve impulses stimulate the posterior pituitary gland to releaseantidiuretic hormone (ADH)
ADH molecules enter the blood and travel throughout the body
ADH causes thekidneystoreabsorbmore water
Thisreduces the loss of water in the urine
How does ADH affect the reabsorption of water in the collecting duct? (5 steps)
Give three ways water is removed from the body? Besides the kidneys
Respiration
Sweating
Blood loss
Explain how the Loop of Henle maintains a graidient of ions which allows H20 to be reabsorbed from filtrate in the collecting duct
- Epithelial cells of descending tubule carry out active transport
-transport sodium ions out of filtrate
-against conc gradient
-into interstitial/tissue fluid
-created/maintains water potential gradient for water reabsorption from collecting duct
-countercurrent multiplier
