The Pituitary Gland (Hypothalamus and the Pituitary Gland) Flashcards
what two organs are the ‘principal organisers of the endocrine system’
hypothalamus
pituitary gland
what connects the hypothalamus and the pituitary gland
a stalk called the infundibulum
the anterior pituitary is a direct extension of what type of tissue
epithelial origin - it is considered a true endocrine gland
the posterior pituitary is an extension of what type of tissue
it is an extension of the neural tissue
what are trophic hormones
trophic hormones govern the release of another hormone
both the hypothalamus and the anterior pituitary gland release trophic and non trophic hormones, true or false
true
not all hormones released by the hypothalamus are neurohormones true or false
false- all hormone released by the hypothalamus are neurohormones
all hormones released by the posterior pituitary are _________
neurohormones
all hormones released by the anterior pituitary are _________
classic endocrine hormones
what are trophic neurohormones
neurohormones secreted into capillaries travelling to anterior pituitary which govern release of anterior pituitary hormones
what are non-trophic neurohormones
neurohormones produced in the hypothalamus and travel to posterior pituitary (via axons of hypothalamic neurons) where they are released into BLOOD
what are the 5 hypothalamic “releasing hormones”
Thyrotrophin Releasing Hormone (TRH)
Corticotropin Releasing Hormone (CRH)
Growth Hormone Releasing Hormone (GHRH)
Gonadotrophin Releasing Hormone (GnRH)
Prolactin Releasing Hormone (PRH)
what are the 2 hypothalmic “inhibiting hormones”
Growth Hormone Inhibiting Hormone (GHIH) aka somatostatin
Dopamine aka Prolactin Inhibiting Hormone (PIH)
what is the hypothalamo-hypophyseal portal system
a network of tiny vessels which transfer trophic hormones from the hypothalamus to anterior pituitary
how is the anterior pituitary connected to the hypothalamus
via capillary portal system
what is the anterior pituitary also known as
adenohypophysis
what is the posterior pituitary also known as
neurohypophysis
the posterior pituitary stores and releases 2 peptide neurohormones what are they
vasopressin (ADH)
oxytocin
where are the neurohormones released by the posterior pituitary synthesised
in the magnocellular neurons
what is the function of vasopressin
regulates water balance
what triggers the release of vasopressin
increase in plasma osmolarity
decrease in plasma volume/blood pressure
what are the 2 sites of action of vasopressin
kidney collecting ducts (increases water reabsorption)
vascular smooth muscle (increased blood pressure)
what is the function of oxytocin
milk ejection and uterine contraction
what triggers the release of oxytocin
labour
suckling
what are the 2 sites of action of oxytocin
milk duct smooth muscle
uterine smooth muscle
what are first degree disorders
those in which the defect is in the cells that secrete the hormone
what are second degree disorders
those in which there is too little or too much trophic hormone from pituitary
what are third degree disorders
relate to hypothalamic defects
6 hormones are released from the anterior pituitary gland (they are all peptides) what are they
- thyroid stimulating hormone (TSH)
- adrenocorticotrophic hormone (ACTH)
- Follicle stimulating hormone (FSH)
- luteinising hormone (LH)
- growth hormone (GH)
- prolactin
what is the only anterior pituitary hormone that isn’t a trophic hormone
prolactin
what is dexamethasone
similar to cortisol, it acts to lower the amount of ACTH released by the pituitary which in turn lowers cortisol secretion from the adrenal gland
what can excess cortisol cause
tissue breakdown
Na+ retention
insulin antagonsim
what tests can be used to diagnose Cushings
24hour urine free cortisol
Dexamethasone test measuring plasma ACTH at the same time
radiology
