9.2 Release of hormones Flashcards
what are the two lobes of the pituitary gland
- Neurohypophysis: posterior lobe (neural tissue): receives, stores and releases hormones from hypothalamus
^ continuation of hypothalamus
- Adenohypophysis: anterior lobe, glandular tissue: synthesies and secretes hormones (involved in stress, growth and reporduction)
what are the 3 major areas of the hypophysis
bit of overview of structure/how thigns are transmittd
PVN (paraventricular nuclei), VH (ventral hypothalamus), SON (supraoptic nuclei)
- primary capillary plexus receives hormones secreted from hypothalamus
- primary ans secondary capillary plexus are connected in series
*hypothalamus projects down to post Pituitaty
describe the anterior lobe of the pituitary
- otupocking of oral mucosa
- no dierct neural contact with hypothalamus
- is a vascular connection, the hypophyseal portal system which has: primary and secondary capillary plexus and hypophyseal portal viens
*hypo releaseshormones into prim cap plex -? travel thru protal veins to anterior pit to sitmulate or inhibt hormone release -> hormoens secreted into secondary cap plexus
what tropic hormones are secreted by the adenohypophysis
*modulate secretion of other hormones
Thyroid-stimulating hormone (TSH):
Adrenocorticotropic hormone (ACTH)
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Growth Hormone (GH)
what non tropic hormones are secreted by the adenophypophysis
- prolactin, Beta-lipotropin, mealnocyte stim hormone (MSH)
what are the endocrine cell types in the adenohypophesis
- Corticotrophs (15-20%)
- produce ACTH (adrenal gland) B-lipotropin (adipocytes) and MSH (melanocytes)
- Thyrotroph (3-5%)
- TSH (thyroid gland)
- Gonadotroph (10-15%)
- LH, FSH (gonads)
- Somatotroph (40-50%)
- GH (all tissues, liver)
- Lactotroph (10-15%)
- PRL (breast gonads)
what hromones are secreted by the hypothalamus to the anterior pituitary
*stim secretion from anterior pituitary
- Corticotropin releasing hormone (CRH): stim ACTH secretion
- Thyrotropin releasing hormone (TRH: sitm TSH and PRL secretion
- Growth hormone stim hormone (GHSH): stim GH secretion
- Somatostatin (GHIH): inhibits GH secretion
- Gonadotropin releaseing hormone (GnRH): stim LH and FSH secretion
- Prolactin releasing hormone (PRH): stim PRL secretion
Prolactin inhib homone (Dopamine): inhibits PRL secretion
Summar of adenohypothyssi action
describe Growth hrmone
- anabolic (building)
- stimulates inrease size and divison of msot cells
- promotes protein synthesis and encourages the sue of fats
- Key targets: liver, bone and skeletal muscle
*effects mediated indirectly by somatomedins (growth promoting protins eg IGF)
metabolic action of HG
- GH released by pituitary to the liver and target tissues
- liver causes formation of IGF-1 (neg feedback to brain)
- > inhibits GHRH release and sitm GHIH release
- IGF-1 can also to to target tissues and modulate things like growth
results of GH secretion
- Skeletal: increased cartilage formation and skeletal growth
- Extraskeletal: inc protin synthesis and cell growth and proliferation
- Fat: inc fat breakdown and release
- Carbohydrate metabolism: inc blood glucose and other anti=insulin effects
what is acromegaly?
- excessive GH section after pubery -> epiphyseal paltes have closed
- get tissue swelling, pigmentation changes, skull expansion
- can be due to pituitary tumour
What is gigantism
- excess GH secretion before closure of epiphyseal plates in long bones
release/ cycle of TH
- Hypothalamus secrets TRH into hypophoseal protal -> to pituitary
- Pituitary releases TSH -> thyroid to release T4 and T3 to modulate cell activity
- free and bound hormone in equlibrium, but the free version causes inhibition at pituitary -> inhibt TSH