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
What hormones does the anterior pituitary gland secrete?
Growth hormone Prolactin TSH ACTH FSH LH
What cells synthesise TSH?
Thyrotrophe cells
What cells synthesis ACTH?
Corticotrophe cells
What cells synthesise FSH?
Gonadotrophe cells
Why is the timing of diagnostic tests important?
Diurnal rhythm
Describe the steps for diagnosis
Signs & symptoms
Biochemical tests
Imaging
Visual field tests
Where is prolactin synthesised?
Lactotrophe cells of anterior pituitary
What does prolactin release inhibiting factor (dopamine) do?
Allows hypothalamic control of prolactin secretion
What stimulates prolactin synthesis?
TRH
What does prolactin do to fertility?
inhibits fertility
What stimulates prolactin secretion?
Mild stress
Nipple stimulation
Coitus
What are the roles of prolactin?
Promote lactation
Development of breast tissue
Excess causes infertility in males and females
What controls the secretion of growth hormone?
The hypothalamus via GHRH and GHRIH
What is GHRIH?
Growth hormone release inhibiting hormone
What stimulates secretion of growth hormone?
Decreased carbohydrates
Decreased fatty acids
Increased amino acids
What is the role of growth hormone?
Promote linear growth of adolescence by increasing protein synthesis and collagen deposition
Foetal growth is relatively independent of GH
Tissue turnover and repair
