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Lecture 44
Hypothalamus-Pituitary-Growth
Term | Definition |
---|---|
Hypothalamus/Pituitary Structure | h at the basis of the brain-stalk connects h to pituitary.posterior pituitary connected by neural axons.anterior pituitary connected by h-hypophysed system |
Posterior Pituitary | hormones synthesized in the hypothalamus.axons and nerve endings in posterior pituitary. |
Vasopressin | secreted when osmolarity inc. inc. h2o reabsorption at collecting duct.stimulates aquaporin insertion time CD membrane. |
Oxytocin | contracts uterus during childbirth.causes milk ejection from mammary glands during lactation |
Hypothalamic Releasing/Inhibiting Hormones | anterior pituitary hormone release controlled by hypothalamus.releasing/inhibiting hormones travel by portal sys to anterior pituitary RH and IH control release of 6 ant pit hormones. |
Portal Sysytem | connects capillary beds from hypothalamus to ant pit. small distance and no dilation means RH and IH released in very small amounts,but w/ big effects. |
Anterior Pituitary Hormone Release | input to the hypothalamus controls RH and IH release.input is both neural and hormonal.balance of rh and ih for particular ant pit hormone controls ant pit hormone release. |
Negative Feedback | anterior pituitary hormone release is regulated by negative feedback-always to ant pit sometimes to hypothal.target gland hormone release inhibits ant pit tropic hormone release |
Growth Control | mult factors-all necess. for full growth.genetics provides base and max.nutrition-most important non-genetic factor:proteins,vitamins,minerals essential for full growth calories needed |
Growth Hormone | protein from anterior pituitary activates second messengers at many organ cell membranes.-15 min circulation time before metabolism by liver. |
Non-Growth Related Effects | inc liver glucose production,inc fatty acid release from adipose tissue:conserves glucose for brain use during growth. |
Growth-Promoting Actions | hyperplasia and hypertrophy of cells inc protein synthesis. |
Bone Growth | growth hormone stimulates bone thickness and length. |
Bone Composition | outer layers have compact bone-ca phos hardens/collagen makes strong and flexible inner layers have spongy bone.long bones epiphyses at both ends,diaphysis in middle. |
Osteoblast/Osteoclasts | o'blasts form new bone and secrete calcium phos.o'clasts read:bone,create spaces in bone. |
Bone Length Growth | length growth-occurs at epiphyseal plates-o'clasts eat epiphyses-o'blasts extend diaphysis.fuse at puberty (o'blasts catch o'clasts) |
Control of Growth Hormone Release | hypothal releases both GHRH and GHIH.diurnal-highest an hr after sleep begins.exercise,physical stress and low blood glucose inc GH release |
GH Deficiency | in children,dwarfism occurs w/ dec. bone growth. no effect on adults. |
GH Excess | before puberty inc proportional growth.after puberty,acromegaly-excess growth of face,hands,and feet. |
Growth Control cont. | growth can catch up during puberty if dec in childhood due to protein catabolism during disease/injury. |