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
release and regulation of adrenocorticotropic hormone
aka corticotropin
*release can be modualted by internal ro external factors like fever, hypoglycemia and stressors
- stressor or CRH from hypothalmus causes ACTH to eb released from anterior pituitary
- Acth -> adrenal gland -> releases cortisol, adrenal medulla releases Noradrenaline and adrenaline
idk the point fo this slide
what are gonadotropins
FSH and LH
- reg functoin of ovaries and testes
- FSH stimulates gemete (egg or sperm) production
- absent fomr the blood in prepubertal boys and girls
- triggered by the hypothalamic gonadotropin releasin hormone (GnRH) during and after puberty
function of gonadotropins in females and males
- Females
- LH works with FSH to cause maturation of the ovarian follicle
- LH works alone to trigger ovulation
- LH promotes synthesis and release of estrogens and progesterone
- In males
- Fsh acts on sertoli cells -> get mature sperm
- LG acts on leydig cells -> get testosterone
Describe prolactin (PRL)
- in females, stimulates milk production by the breasts
- Triggered by the hypothalamic prolactin-releasing hormone (PRH)
- Inhibited by prolactin-inhibiting hormone (PIH, dopamine)
- Blood levels rise toward the end of pregnancy
- Suckling stimulates PRH release and encourages continued milk production
key features of the posterior pituitary
- paraventicular nucleus
- supraoptic nucleus
- infundibulum
- hypothalamic hypophyseal tract
secretion of hormones from posterior pituitary
- Hypothalamus neurons synthesize oxytocin and ADH
- Oxytocin and ADH are transported along the hypothalamic-hypophyseal tract to the posterior pituitary
- Oxytocin and ADH are stores in axon terminals in the posterior pituitary
- Oxytocin and ADH are released itno the blood when hyophalamuc neurons fire
describe oxytocin
- released by posterior pituitary
- regulated by postiive feedback
-
- Leads to increased intensity of uterine contractions during birth
- Synthetic and natural oxytocin drugs are used to induceor hasten labor
- triggers milk ejection (“letdown reflex”) inwomen producing milk
- Plays a role in sexual arousal and satisfaction in males and non-lactating females
describe ADH
antidiuretic hormone (released by posterior pituitary)
- Plasma osmolality is monitored by osmoreceptors in the hypothalamus (PVN and SON)
- high solutes leads to ADH release preserving water
- low solutes inhiibt ADH release cusing water loss
- Alcohol inhibits ADH release and causes copious urine output
- ADH secretion also sitmulate by large decrease in blood volume/blood pressure
