5-Pituitary gland Flashcards
Structure
Uneven ball sack shape, anterior is the bigger ball
Size of a large pea
Buckle tissue forms anterior sack
Neural tissue derived from rafkai pouch forms posterior
Tumor on pituitary
Can’t press downwards due to sphenoid bone (sella turcica)
Presses upwards on optic nerve
Tropic vs Non-tropic
Tropic acts on another endocrine gland
Non-tropic acts directly on body
Anterior pituitary hormones
FLAT PIG (first ones tropic, last 2 non-tropic)
Follicle Stimulating Hormone(FSH)
Luteinising Hormone(FH)
Adrenocorticotropic Hormone(ACTH)
Thyroid Stimulating Hormone(TSH)
Prolactin(PRL)
I
Growth Hormone(GH)
Acidophils
Secrete Gh and PRL
Somatotropes-GH
Located laterally, 40-50% of all cells
Lactotropes-PRL
Randomly distributed, 10-25% of cells
Proliferate in pregnancy, mammary gland formation
Stimulated by oestrogen
Basophils
Secrete FSH, LH, ACTH, TSH
Thyrotropes-TSH
Found laterally, 3-5% of cells
Corticotropes-ACTH
Found in centre, 15-20% of cells
Gonadotropes-LH, FSH
Found randomly, 10-15%
Chromophobes
In anterior pituitary
Don’t take up colour
Secretory cells in the process of building up hormone stores
ACTH synthesis
From POMC gene
Pro-opiomelanocortin
chopped down by pro-hormone convertase 1&2
ACTH release
Corticotropin Releasing Hormone released from hypothalamus
From paravicellular hypothalamic neurones
Binds to CRH-R1 GCPR (Gs)
Activates adenylate cyclase
cAMP
PKA causes transcription of POMC gene
Product stored
If CRH signal is big enough, ACTH released
Vasopressin works on V3 receptor GCPR (Gq)
Activates IP3 pathway
Intracellular Ca increases which leads to release of ACTH
ACTH control and feedback loops
Ultra-short feedback loop from CRH
Short loop feedback
Long loop feedback
Pulsal time can vary a lot between hormones
Diurnal control mediated by superchiasmatic nucleus(SCN)
Endogenous clock genes in many tissues
Entrained by light/dark
GH secretion
Hypothalamus releases GHRH
Somatotropes release GH
Can act on liver to produce IGF-1
Hypothalamus releases somatostatin
inhibits somatotropes from releasing GH
Sleep increases GHRH
FFA increases somatostatin
Oestrogen increases somatotrope sensitivity to GHRH
PRL secretion
Hypothalamus releases TRH
Causes Lactotropes to release prolactin
acts on mammary gland
Hypothalamus releases dopamine
inhibits lactotropes from releasing prolactin
Suckling triggers PRL release
TSH secretion
Hypothalamus releases TRH
Thyrotropes release TSH
Diurnal release (overnight)
Stresses decrease release
T3 and T4 have a short and long feeback loop
LH and FSH secretion
Hypothalamus pulsatile release of GnRH
Gonadotropes release FH and FSH
In men-
Testosterone synthesis
Spermatogenesis
Testosterone has long and short loop feedback
Testes inhibit gonadotropes
PRL stops hypothalamus and anterior pituitary
In women-
Oestrogen and progesterone synthesis
Menstrual cycle
Oestrogen can have positive and negative feedback loops depending on stage of menstrual cycle
PRL inhibits both hypothalamus and anterior pituitary
