pituitary gland Flashcards
Describe polypeptide hormones
- less than 100 amino acids
- water soluble
- bind to receptors on cell membrane
describe protein hormones
- more than 100 amino acids
- water soluble
- bind to receptors on cell membrane
steroid hormones
- derived from cholesterol
- lipid soluble
- bind to receptors on the cell cytoplasm or in the cell nucleus
amine hormones
- amino-acid derived from tyrosine (norepinipehrine etc)
- water soluble
- bind to receptors on cell membrane
thyroid hormones
- derived from amino acid tysosine and contain iodine
- water soluble
- bind to receptors on cell membrane
describe ACTH (adrenocorticotropic hormone)
- anterior pituitary hromone
- stimulates synthesis of adrenocortical hormones (cortisol, androgens and aldosterone)
- accelerates melanin synthesis (causes hyperpigmentation)
- androgens do not fee-back inhibit ACTH secretion
Describe TSH (thyroid stimulating hormone)
- stimualtes synthesis and secretion of thyroid hormones
- TRH from hypothalamus stimulates the secretion of TSH
describe FSH (follicle-stimulating hormone)
- in females causes growth of follicles in the ovaries
- in males causes sperm maturation
describe LH (luteinizing hormone)
- in males causes stimulation of testosterone synthesis in testes
- in females causes stimulation of ovulation, formation of corpus luteum and estrogen and progesterone synthesis in ovaries
Describe GH or somatostatin (growth hormone)
- inhibit action of GHRH (hypothalamic growth hormone-releasing hormone)
- stimulates protein synthesis and overall growth of most cells and tissues
- stimulates production of insulin-like growth factors (IGF)
describe prolactin (PRL)
- promotes development of female breast and milk
- not a tropic hormone
- thyrotropin releasing hormone (TRH) stimulates the release of prolactin
what are the two posterior pituitary hormones
- arginine vasopressin (AVP) or antidiuretic hormone (ADH)
- Oxytocin
describe oxytocins effect on milk-let down reflex
- afferent signals from the nipples when infant is suckling causes release of oxytocin
- oxytocin causes milk-let down reflex
- myoepithelial cells lining the breast ducts contract causing milk ejection
describe oxytocins effect on childbirth
- by term of pregnancy the mother’s uterus has experienced upregulation of # of oxytocin receptors
- -> distension of cervix anc contraction of uterus stimulates release of oxytocin
- -> results in positive feedback and the release of more oxytocin which further increases contractility of the uterus (aids in the delivery of the baby and the involution of the uterus)
what are the ways hormones are cleared from the blood
- Metabolic destruction by the tissue or by enzymes in the blood
- binding to tissues
- excretion by the liver into bile or kidneys into urine
- water soluble hormone will be filtered at the kidney glomerulus, so hormones bound to plasma proteins tend to have much longer half lives in the blood
define neurogenic diabetes
- caused by a problem in the hypothalamus or the connection between the hypothalamus and the posterior pituitary
- -> defect which interfere with the production or release of AVP
- -> trauma, infection and cancer can also prevent AVP release
- little or no ADH can reach the kidneys, the collecting ducts cannot produce concentrated urine
Define nephrogenic diabetes
- caused by problem in the kidneys themselved
- mutation that affects the V2 receptor for ADH on the collecting duct cells
- -> mutation that affects production and insertion of aquaporins (aquaporins are need to produce concentrated urine)
what are the metabolic effects of growth hormones
- increased rate of protein syntheisis (enhance amino acid transport, RNA translation, transcription of DNA, decreases breakdown of cell protein)
- increased release of fatty acid from adipose tissue (used for energy)
- DECREASE use of glucose
- -> increase glucose synthesis by liver
- -> increase insulin secretion
describe the effects of growth hormone on the bones
- growth hormones strongly stimulates osteoblasts so bone can continue to grow THICKER throughout life
describe IFG (insulin growth factor)
- called somatomedin C
- liver is the main site of synthesis
- Somatomedin C attaches strongly to carrier protien and has much longer half-life than GH
- GH causes production and release of IGF in the liver
- GH exert much of its effects through action of IGF
define panhypopituitarism
- abnormality of growth hormone secretion
- acquired form pituitary tumor that destorys the pituitary gland
Define Hyperpituitarism (acromegaly
- results of excessive secretion of GH after normal completion of body growth
- resutls in overgrowth of bone in the face, head and hands
describe the effects of too much and too little GH
- Giatism = too much GH
- Dwarfism = too little GH (inability to form somatomedin C)
