Anterior Pituitary Flashcards
When does the hypothalamus secrete corticotrophin releasing hormone and what does it do
- when scared, infected, bloodless ;)
- to act on corticotropes in the anterior pituitary which secrete ACTH (adrenocorticotropin hormone)
What receptor does ACTH bind to on adrenal glands and where does this come from
Melanocortin receptor 2 from POMC producesing melanocyte stimulating hormone (MSH)
What inhibits ACTH and what does ACTH stimulate
- dexamethasone
- cholesterol desmolase and lipoprotein uptake in cortical cells
What receptor is MC2R
GPCR
How is ACTH made and what else is made w it
In pituitary cells prepropriomelancortin is cleaved into propriomelanocortin (POMC) which makes ACTH, MSH, endorphins (endogenous opioids), enkephalins(pain sensors- peptides)
What does cortisol being hydrophilic and lipophillic mean and what does it do in cytoplasm to get to DNA
- travel in plasma and can cross phospholipid bilayer
- binds to gulcocortoid receptor (nuclear R dimerised) in cytoplasm allowing it to dissociate from chaperone and enter nucleas to bind with glucocortoid response elements of genes to change expression
What does ant pit produce and what stims it
GH, TSH, FSH, LH, ACTH, PRL, MSH
Hypothalamus releases hormones into surrounding intestitial fluid whihc permeates into nearby fenestrated capillaries which form hypophyseal portal system that extends into anterior pit
What is somatotropin, when does it get secreted and what stims it
- GH
- morning/ oestrogen/ testosterone
- GHRH from hypothalamus into hypopheaseal portal system to ant pit somatotroph cells to release GH
How is GH release controlled
- neg feed when increase GH releases lots of somatomedins from tissues causing hypothalamus to decreases GHRH production
- somatostatin blocks GHRH from acting on soamtroph cells in pit, inhibits insulin and glucagon (beta alpha), and vasocactive peptides in delta pancreas
What are GH direct effects in adipose liver tissues
- lipolysis, gluconeogenesis and glycogenolysis and in tissues insulin resistance increases prompting more glucose which increases insulin (diebetogenic)
What are GH indirect anabolic effects via IGF1
When somatomedin C is stumated (IGF1) which binds to IGFR and insulin receptors prompting metabolism and previewing cell death, increasing division
- protein uptake and muscle growth
- epiphyseal cartilage osteoblasts and chondrocytes effect
- cardiac function
- glucose after meal taken in by insulin for ATP synthesis while IGF1 binds to plasma membrane receptors to increase aa uptake
What receptor does GH bind to in the liver
TK associated receptors leading to IGF1 release for bone and muscle growth
What is the hypothalamic pit Gondal axis
GnRH from hypo
LH FSH from pit
Oes and test from gonads
What is the action of LH and FSH in males
- LH stims leydig cells to produce testosterone and turn to dihydrotesterone (DHT) which has a negative feedback loop on hypo and pit
- FSH drives sperm from Sertoli cells and supports androgen binding protein (ABP) which maintains high testosterone in tubules, P450 aromatise which returns test to oestradiol, GF that support sperm cells mobility and fertility and negative feedback on FSH acting as a GF for leydig cells
LH and FSH in females
Stimulate overly to produce mature gametes and synthesis oestrogen and progesterone
- LH binds to theca cells on developing follicles and granules cells then after ovulation, LH binds to corpus luteum- basically it matures and releases eggs
- FSH binds to granulosa cells to increase steroid hormone production (LH and FSH) enzymes and follicle growth increases and increase activins production causing pos feedback on ant pit while inhibins produce negative feedback on pituitary, help androgens go to oestrogen
What does theca cells do
Produce progestins and androgens to enter granules cells to be converted to oestrogens
Oestrogen on feedback loops with high levels and w prog
- oest neg feedback on LH and FSH
- high levels is pos (ovulate)
- with prog is neg ( so less LH so less prog causing menstruation)
What cells produce lactin and what its role
- lactotroph cells
- breast development and milk production
What makes prolactin different from other anterior pituitary hormones
No stimulating factor from hypothalamus
What makes prolactin different from other anterior pituitary hormones
No stimulating factor from hypothalamus
What inhibits prolactin, acting as what
What stimulates prolactin (disinhibition) and another 2
- dopamine inhibits
- acting as a PRL inhibitory factor (PIF)
- suckling acts on afferent pathways whihc inhibit dopaminegenic neurons in hypothalamus (disinhibition) and TRH from hypothalamus and oestrogen increases lactotroph sensitivity to TRH which decreases their sensitivity to dopamine inhibition
Why dont u have period while breastfeeding
Decreases GnRH realised by hypothalamus which decreases FSH and LH
Why dont u have period while breastfeeding
Decreases GnRH realised by hypothalamus which decreases FSH and LH
What does T3 and T4 do to met rate, cardiac muscle protein synthesis and mineralisation
- increases rate as is catabolic- lipolysis, glyconeogenesis, glycolysis, proteolysis
- increases cardiac and acts on beta 1 receptors to increase CO
- increases bone mineralisation
How does T3 get to nucleas
Binds to nuclear receptor to stimulate transcription and binds to thyroid regulating element
