HYPOTHALAMUS, PITUITARY AND NEUROSECRETION Flashcards
(10 cards)
How does the hypothalamus control the pituitary gland? (1)
By releasing a number of controlling hormones from its special neurosecretory cells into the portal vein that supplies the anterior lobe of the pituitary.
What are neurosecretory cells? (1)
Modified neurones producing and transporting hormones
How does the pituitary secrete these hormones? (1)
The posterior. Lobe of the pituitary gland does not synthesise hormones but stores releases hormones synthesised by the hypothalamus, these hormones are transported to the posterior pituitary along modified neurones and stored in the vesicles found at the end of these specialised neurosecretory fibres within the gland.
What causes the release of these hormones in the pituitary gland? (1)
Impulses from the hypothalamus cause the release of specific hormones into the blood in the capillary network.
Where is ADH synthesised? (1)
In the hypothalamus and transported by neurosecretory cells to the posterior pituitary
How does ADH act? (1)
It is a peptide hormone and acts by binding to receptor sites on the cells of the collecting ducts and by the use of a second messenger triggers the insertion of intergral membrane protein channels called aquaporins
What are aquaporins? (1)
Intergral proteins that form channels to allow the free passage of water molecules through the phospholipid bilayer.
How do aquaporins allow water molecules to diffuse? (1)
They increase the rate of osmosis, This is because the water molecules no longer have to pass through the lipoprotein structure that restricts their flow.
What effect does ADH have on osmosis? (1)
Ensures that a maximum volume of water can be reabsorbed in the medulla of the kidney and back into the bloodstream.
How are hormones like ADH removed? (1)
Are removed from the bloodstream and broken down by the liver, this means that continual secretion is needed to retain its effect on the kidney and allow the hypothalamus to retain accurate control.
