T1 L2 Intro to hypothalamic-pituitary axis Flashcards
What is a consequence of an enlargement of the pituitary gland?
Presses on optic chasm leading to visual defects
Describe the location of the pituitary gland
Below the brain, encased in the skull
Hypothalamus is directly above
How is the pituitary gland connected to the brain?
Infundibulum
What is neurohypophysis?
Posterior pituitary
Down-growth from the brain
What does the neurohypophysis secrete?
ADH
Oxytocin
Where are ADH & oxytocin synthesised?
By neurons of the hypothalamus (supraoptic nuclei and paraventricular nucleus)
Describe the path of ADH and oxytocin to the posterior pituitary
Inactive hormones are transported from the supraoptic and paraventricular nuclei
Along hypothalamico-neurohypophyseal tract to the posterior pituitary for storage
What influences the secretion of ADH?
Plasma osmolarity
What occurs when v2 receptors are stimulated?
Translocation of aquaporins to membrane of kidney tubule leading to water reabsorption
What occurs when v1 receptors are stimulated?
Vasoconstriction
What is the consequence of a disorder of ADH secretion?
Disorders of fluid balance
When is oxytocin important?
During parturition & lactation
What is an increase oxytocinase activity important in early pregnancy?
The levels of oxytocin rise so it breaks down oxytocin to prevent parturition
Describe the effect of oxytocin during parturition
1) Acts on G-protein linked receptor to cause calcium influx.
2) Contraction of myometrium
3) Increased stimulation of stretch receptors in uterine wall
4) Expulsion of foetus
5) Stimulation of cervix & vagina
6) Oxytocin production
Describe the effect of oxytocin during lactation
1) Acts on G-protein linked receptor to cause calcium influx
2) Contraction of smooth muscle of myoepithelium
3) Milk let down
4) Suckling
5) Nipple stimulation
6) Oxytocin production
