the pituitary gland Flashcards
the hypohalamo-pituitary axis
hypothalamus and pituitary are principal organisers of the endocrine system
hypothalamus is part of brain and connected to pituitary gland below
hypothalamus neuroendocrine function
part of its function is to release chemicals into blood that act at distal sites
as hypothalamus is made of neural tissue, any chemicals it releases must be neurohormones
hypothalamus
integration centre for endocrine systems
connected to pituitary via stalk (infundibulum)
how does hypothalamus communicate with anterior pituitary and poosterior pituitary
hypothalamic axons and nerve terminals project to and from posterior pituitaty
connection with anterior pituitary is via neurohormones (via capillary portal system)
pituitary gland
bean shaped and size
located in a pocket in sphenoid bone, directly below hypothalamus
2 distinct types of tissues - anterior and posterior
difference between anterior and posterior pituitary
posterior is extension of neural tissue
anterior is a true endocrine gland of epithelial origin
anterior pituitary
connected to hypothalamus via capillary portal system
also called adenohypophysis
true endocrine, epithelial origin
makes up 2/3rds of glan
posterior pituitary
continuation of hyopthalamus, consits of axons and nerve terminals of hypothalamic neurones
secretes neurohormones made in hypothalamus
neuroendocrine
aka neurohypophysus
makes up 1/3 of gland
parta intermedia
bit inbetween anterior and posterior pituitary
secretes melanocyte stimulating hormone
tropic hormones
tropic hormones govern the release of another hormone
hormone type released from hypothalamus
neurohormone
hormone type released from posterior pituitarty
neurohormone
hormone type released from anterior pituitary
classic endocrine hormones
non-tropic hormones
do not have intermediate hormone in pathway
just go off to target and elict a responese
hypothalaic neurohormones: 2 forms
non-tropic
tropic
hypothalamic neurohormones: non-tropic
neurohormones produced in hypothalamus and travel to posterior pituitary (via axons of hypothalamic neurones) where they are released into blood
hypothalamic neurohormones: tropic
neurohormones secreted into capillaries travelling to anterior pituitary
govern release of anterior pituitary hormones
the hypothalamic non-trophic hormones and posterior pituitary
vasopressin (ADH)
oxytocin
ADH (vasopressin)
maintaines water balance
oxytocin
stimulates uterine contraction at parturiton and aids expression of milk in lactating brease
hypothalamic trophic hormones: the ‘releasing’ hormones
thyrotropin releasing hormone (TRH) corticotropin releasing hormone (CRH) growth hormone releasing hormone (GHRH) gonadotropin realsing hormone (GnRH) prolactin releasing hormone (PRH)
hypothalamic trophic hormones: the ‘inhibiting’ hormones
growth hormone inhibiting hormone (GHIH) aka somatostatin
dopamine aka prolactin inhibiting hormone
hypothalamo-hypophyseal portal system
network of tiny vessels which transfer trophic hormones from hypothalamus to anterior pituitary
short distance - rapid and dynamic
what is production of anterior pituitary hormones controlled by
hypothalamic trophic hormones that either stimulate or inhibit hormone production
the anterior pituitary hormomea
thyroid stimulating hormone (TSH) aka thyrotropin adrenocorticotrophic hormone (ACTH) follicle stimulating hormone (FSH) luteinising hormone (LH) growth hormone (GH) prolactin
which of the anterior pituitary hormones are trophic
TSH ACTH FSH LH GH
what does prolactin do
directly stimulates milk production from the breast during lactation
long-loop feedback
feedback from endocrine target
short-loop feedback
feedback from anterior pituitary to hypothalamus
1ry endocrine disorders
those in which the defect is in cells that secrete the hormone
2ry endocrine disorders
those in which there is too little or too much trophic hormone from pituitary
3ry endocrine disorders
relate to hypothalamic disorders
hyporesponsiveness endocrine disorders
alterations in receptor for hormone, disordered post-receptor events. failure of metabolic activation of hormone or antagonistic events
hyperresponsiveness endocrine disorders
could be due to permissive. effects e.g. thyroid hormone ++ adrenaline meadiated lipolysi s
permissive effects
the presence of one hormone enhances the effect of another
antagonistic effect
the presence of one hormone reduces the effect of another