Hypothalamus and Pituitary Flashcards
what part of the pituitary releases neurohormones?
the posterior pituitary
what is the infundibulum?
the stalk connecting the hypothalamus to the pituitary
what two forms of hypothalamic neurohormones are there?
> tropic
> non-tropic
what are tropic hormones?
Hormones which regulate the release of other hormones
what are non-tropic hormones?
Hormones which act directly on tissue to cause a change in activity
how is the anterior pituitary connected to the hypothalamus?
capillary portal system
what is the origin of the anterior pituitary?
epithelial
what is the origin of the posterior pituitary?
neural
name 5 hypothalamic releasing hormones
> prolactin releasing hormones > gonadotropin releasing hormones > corticotropin releasing hormones > thyrotropin releasing hormone > growth hormones releasing hormone
name 2 hypothalamic inhibiting hormones
> dopamine (prolactin inhibiting hormone)
> growth hormone inhibiting hormone (somatostatin)
describe the hypothalamic-hypophyseal portal system
> network of tiny vessels
2 capillary beds connected in series
rapid due to short distance
small amount of neurosecretory neurons sufficient for control
where do hormones from neurons enter the hypothalamic-hypophyseal portal system?
at the median eminence
name 5 anterior pituitary hormones
> prolactin > thyroid stimulating hormones > adenocorticotropic hormone > growth hormone > follicle stimulating hormone (luteinising hormone)
what is the action of prolactin?
targets the breasts and causes lactation
what is the effect of adenocorticotropic hormone?
targets the adrenal cortex:
> triggers cortisol release
what is the effect of growth hormone?
targets the liver:
> IGF-1 release
> tissue metabolism
what are the effects of follicle stimulating hormone and luteinising hormones?
targets the gonads:
> sex hormone release
> regulates reproductive function
name 3 integration centres in the anterior pituitary feedback control loop
> hypothalamus
ant. pituitary
target endocrine cells
what is the long loop feedback in anterior pituitary control?
negative feedback from the endocrine target by hormones acting on the hypothalamus
what is the short loop feedback in control of the anterior pituitary?
negative feedback loop: hormones released by the anterior pituitary act on the hypothalamus
what is the function of the posterior pituitary?
stores and releases 2 neurohormones:
> vasopressin
> oxytocin
where are oxytocin and vasopressin synthesised?
in the magnocellular neurons in the hypothalamus that run through the infundibulum and terminate on capillaries directly
what triggers the release of vasopressin?
> increased plasma osmorality
> decreased plasma volume and blood pressure
what are the effects of vasopressin?
regulates water balance:
> acts on kidney collecting ducts increasing water reabsorption
> constricts vascular smooth muscle causing increased blood pressure
what is oxytocin release triggered by?
> babies head against the cervix
> suckling
what are the effects of oxytocin?
> contraction of milk duct smooth muscle causing milk ejection
acts on uterine smooth muscle in childbirth
describe a primary endocrine disorder
there is a defect in the cells that are secreting the hormone
describe a secondary endocrine disorder
there is too little or too much trophic hormone from the pituitary
describe a tertiary endocrine disorder
there is a defect in the hypothalamus
