The Pituitary Gland Flashcards
what are the “master controllers” of the endocrine system?
The hypothalamus and pituitary
what connects the hypothalamus to the pituitary?
stalk called the infundibulum.
how big is the pituatary gland?
14 mm diamete
what are the two types of tisue in the pituitary gland?
anterior and posterior pituitary
what are the functions of hypothalamus?
cold stress metabolic demand hydration status exercise day/night menstrual cycle sleep breastfeeding pregnancy puberty
what do hypothalamus and anterior pituitary release?
tropic and non-tropic hormones (tropic hormones govern the release of another hormone)
what are all the hormones released by the hypothalamus?
neurohormones
what are all the hormones released by the posterior pituitary?
neurohormones
what are all the hormones released by the anterior pituitary?
classic endocrine hormones
what are the 2 forms of hypothalmic neurohormones?
tropic and non-tropic
what are tropic neurohormones?
neurohormones secreted into capillaries travelling to anterior pituitary. Govern release of anterior pituitary hormones
what are non-tropic neurohormones?
neurohormones produced in the hypothalamus and travel to posterior pituitary (via axons of hypothalamic neurons) where they are released into blood
where do all hypothalamic tropic hormones bind to?
receptors on anterior pituitary and stimulate/inhibit release of AP hormones
what are the 5 trophic hypothalmic releasing hormones?
Thyrotropin Releasing Hormone (TRH) Corticotropin Releasing Hormone (CRH) Growth Hormone Releasing Hormone (GHRH) Gonadotropin Releasing Hormone (GnRH) Prolactin Releasing Hormone (PRH)
what are the 2 trophic hypothalmic inhibiting hormones?
Growth Hormone Inhibiting Hormone (GHIH) aka somatostatin
Dopamine aka Prolactin Inhibiting Hormone (PIH)
what are the 2 hypothalmic inhibiting hormones?
Growth Hormone Inhibiting Hormone (GHIH) aka somatostatin
Dopamine aka Prolactin Inhibiting Hormone (PIH)
are all of these hypothalmic hormones peptides?
yes except dopamine
what is the hypothalamo-hypophyseal portal system?
Network of tiny vessels which transfer trophic hormones from hypothalamus to anterior pituitary
what type of tissue is the anterior pituitary?
true endocrine tissue
epithelial origin
how is the anterior pituitary connected to the hypothalmus?
via capillary portal system
what is the anterior pituitary also called?
adenohypophysis
which part of the pituitary gland makes up 2/3rds of the gland?
anterior
what type of tissue is the posterior pituitary gland?
neuroendocrine tissue
what is the tissue origin of the posterior pituitary gland?
neural
what is the connection betwen posterior pituitary and hypothalamus?
neural connection
what is the posterior pituitary gland also called?
neurohypophysis
what is the production of the anterior pituitary hormones controlled by?
hypothlamus
how many hormones are released from the pituitary gland?
6
how many of these hormones are tropic hormones that are releaased from anterior pituitary gland?
5/6
what are the anterior pituitary hormones?
Thyroid Stimulating Hormone (TSH) aka thyrotropin
Adrenocorticotrophic Hormone (ACTH) aka corticotropin
Follicle Stimulating Hormone (FSH)
Luteinising Hormone (LH)
Growth Hormone (GH)
Prolactin
which of the anterior pituitary hormones are not tropic hormones?
prolactin
what does prolactin do?
directly stimulates milk production from the breast during lactation
action of prolactin
breast –> lactation (direct)
action of thyeoid-stimulating hormone
thyroid –> TH release (tropic)
action of adrenocorticotropic hormone?
ad. cortex –> cortisol release (tropic)
action of the growth hormone
liver –> IGF-1 release (tropic) and tissue metabolism (direct)
action of the follicle-stimulating hormone luteinising hormone?
gonads –> regulation of reproductive function (direct) and sex hormone release (tropic)
what are the integration centres that control the anterior pituitary feedback control?
hypothalamus
anterior pituitary
target endocrine cell
how does the anterior pituitary feedback control work?
hormones themselves act as negative feedback signal
each hormone feeds back to inhibit hormone secretion by integrating centres earlier in the reflex
feedback from endocrine target = long-loop feedback
feedback from anterior pituitary to hypothalamus = short-loop feedback
what are the peptide hormones that the posterior pituitary stores and releases?
vasopressin (ADH)
oxytocin
where are the posterior pituitary neurohormones synthesised?
magnocellular neurons which have their cell bodies in specific areas of the hypothalamus
how do the axons get to the posterior pituitary?
project down the infundibulum
what type of hormones do oxytocin and vasopressin behave like?
typical peptide hormones
what is vasopressins main function?
regulates water balance
the release of vasopressin is triggered by?
increase plasma osmolarity and decrease plasma volume/blood pressure
what is the site/mode of action of vasopressin?
kidney collecting ducts
increases water absorption
vascular smooth muscle
increase blood pressure
what is the function of oxytocin?
milk ejection and urine contraction
the release of oxytocin is triggered by?
labour
suckling
site/mode of action of oxytocin?
milk duct smooth muscle
contracts muscle- ejecting milk
urine smooth muscle
child birth
what is hyposecretion?
too little hormone secreted
hypersecretion
too much hormone secreted
hyporesponsiveness
reduced response of the target cell
hyperreponsiveness
increased response of the target cell
what does hyporesponsiveness relate to?
relates to alterations in receptor for hormone, disordered post-receptor events or failure of metabolic activation of hormone, (where this is required for function).
what does hyperresponsiveness relate to?
could be due to permissive effects e.g. Thyroid hormone ++ adrenaline mediated lipolysis.
what are 1st disorders?
are those in which the defect is in the cells that secrete the hormone
what are 2nd disorders?
are those in which there is too little or too much trophic hormone from pituitary
what are 3rd disorders?
relate to hypothalamic defects
what kind of neurons does the posterior pituitary contain?
magnocellular neurons which have their cell bodies in the hypothalamu
magnocellular neurons store and releases 2 peptide neurohormones. What are they?
vasopressin
Oxytocin
how do vasopressin and oxytocin behave?
as typical peptide hormones
how is anterior pituitary connected to hypothalamus?
Connected to hypothalamus via hypothalamic-hypophyseal portal system
