Pituitary And Hypothalamic Control Flashcards
Anterior pituitary originates from the invagination of pharyngeal epithelium
Rathke’s pouch
hence made up of epitheloid cells
Posterior pituitary originates from the
called
neural tissue outgrowth from hypothalamus pituicytes
hence made up of glial cell
Cell: somatotropes
Stimulates body growth, secretion of IGF-1, lipolysis
Inhibits action of insulin on carbohydrates and lipid metabolism
Promotes growth of entire body by affecting protein formation, cell mutliplication and differentiation
Growth hormone
Cell: Corticotrope
Stimulates production of glucocorticoids and androgen by adrenal cortex
Maintains size of zona fasciculata and reticularis of cortex
Controls secretion of some of the adrenocortical hormones which affect the metabolism of glucose, proteins and fats
Adrenocorticotropic hormone
Corticotropin
Cell: Thyrotropes
Stimulates production of thyroid hormones by thyroid follicular cells
Maintains size of follicular cell
Controls rate of secretion of thyroxine and triiodothyronine by thyroid glands
Control rates of intracellular chemical reaction
Thyroid stimulating hormone
Thyrotropin
Cell: Gonadotrope
Stimulates development of follicle, regulates spermatogenesis in testes
Follicle stimulating hormone
Cell: Gonadotrope
Causes ovulation and formation of corpus luteum in ovary
Stimulates production of estrogen and progesterone by ovary
Stimulates testosterone production by testes
Luteinizing hormone
Cell: lactotropes
mammotropes
Stimulates milk secretion and production
Prolactin
Secreted by posterior pituitary
Controls rate of water excretion into urine helping to control concentration of water in the body fluids
Antidiuretic hormone
Vasopressin
Secreted by posterior pituitary
Helps express milk from glands of breast to nipple during suckling and helps in delivery of baby at end of gestation
Oxytocin
Stain strongly with acid dyes called
Thus pituitary tumors secrete large quantities of human growth hormones are
Somatotropes
Acidophils
Acidophilic tumor
Cells bodies secreting posterior pituitary hormones are located on the hypothalamus and called
Magnocellular cells
Supraoptic nuclei
Paraventricular nuclei
Secretion from posterior pituitary is controlled by nerve signals that originate in the hypothalamus and terminate in the
Meanwhile, secretion by anterior pituitary is controlled by hormones called via
posterior pituitary
Hypothalamic releasing and inhibitory hormones by hypothalamic-hypophyseal portal vessel
Highly vascular with extensive capillary sinuses
Flows through hypothalamic hypophysial portal blood vessel into ant pituitary sinus through median eminence
Anterior pituitary
Electrical stimulation of this region excites nerve endings and cause the release of all hypothalamic hormones
Median eminence and tuber cinereum
Almost all of the anterior pituitary hormones rely on the releasing hormone except
which is controlled by inhibitory hormone
and the GH which is inhibited by
Prolactin
somatostatin
All major anterior pituitary hormones exert their principal effect by stimulating target glands except
growth hormone exerts its effect directly on all of body tissues
GH metabolic effects
1 inc rate of protein synthesis
2 inc mobilization of fatty acid from adipose, inc fatty acid in blood and inc fatty acid for energy
3 dec rate of glucose utilization
GH promotes protein synthesis by
Enhancing AA transport through cell membranes
Enhancing RNA translation to cause protein synthesis by ribosomes
Inc nuclear transcription of DNA to form RNA (most important)
Dec catabolism of protein and amino acid
GH also causes this effect on fat stores
Promotes utilization of fat over carbohydrates and protein
Excessive GH amount may cause ketogenic effect and fatty liver
GH causes these effects on carbohydrate
1 dec glucose uptake in skeletal ms and fat
2 inc glucose production by liver
3 inc insulin secretion
Insulin resistance = diabetogenic, hyperglycemia and compensatory inc in insulin secretion bec probably of elevated FA dec sensitivity of liver and skeletal ms
GH fails to cause growth if there is lack of
pancreas
carbohydrate exclusion from diet
GH has these effects on bone
1 inc deposition of protein by chondrocytic and osteogenic cells causing growth
2 inc rate of reproduction of these cells
3 specific effect of converting chondrocytes into osteogenic cells causing deposition of new bone
Two principal mechanism of bone growth by GH
1 deposition of new cartilage then conversion into new bone elongating shaft at epiphyses
2 osteoblast deposition making bones thicker esp in membranous bones greater than osteoclast resorption
GH exerts its growth effect through
Somatomedin C
Insulin like growth factor
GH is secreted in this pattern
Pulsatile inc and dec
Deficiency or inability to secrete somatomedin C causes
pygmy stature in Africans
Levi-Lorain dwarf
GH is secreted during these states
1 starvation with protein deficiency 2 hypoglycemia or low fatty acid 3 exercise 4 trauma 5 excitement 6 ghrelin 7 inc blood AA 8 testosterone, estrogen 9 deep sleep first two hours (stage II, IV)
Inhibits GH release
Somatomedin ILGF
GH exogenous
GH IH
Aging obesity inc blood fa and glucose
Part of hypothalamus that cause secretion of GH
Sensitive to blood glucose conc
Causes satiety in hyperglycemic state and hunger in hypoglycemic states
Ventromedial nucleus
GHRH stimulates secretion of GH in cells by
Attaching to cell receptor on outside surface of GH cells in pituitary
Activate adenylate cyclase
Inc cAMP
Inc Ca ions and release of hormone into blood
Long term effect: transcription in nucleus by genes to synthesize new hormone
Major long term controller of growth hormone secretion
Protein nutrition
Dec secretion of all hormones of anterior pituitary from congenital or by tumor
Panhypopituitarism
Generalized def of anterior pituitary secretion during CHILDHOOD
Proportional but slowed growth rate usually due to panhypo
Dwarfism
Causes of panhypopituitarism in adults
1 craniopharyngioma
2 chromophobe tumor
3 Sheehan syndrome
Panhypopituitarism on adult may present
1 lethargic person
2 weight gain
3 loss of sexual function
Acidophilic GH producing tumor before adolescence
Hyperglycemia, DM
Gigantism
Acidophilic tumor after adolescence
Thicker bones, marked enlargement if hands and feet and membranous bone such as skull, nose, bosses of forehead
Acromegaly
ADH is formed primarily in the of the hypothalamus
supraoptic nuclei
oxytocin is formed primarily in the of the neurohypophysis
paraventricular nuclei
Hormones of the pituitary are synthesized in the hypothalamus and bound to carrier proteins called
neurophysin
ADH secretion is controlled by osmoreceptors in the
through
organum vasculosum
vascular organ of lamina terminalis (VOLT)
supraoptic crest
osmolarity
Stimulates vasopressin secretion
Low blood volume by 15-25%
Dec stretch of baroreceptors of carotid aortic and pulmo regions
Stimulates contraction of pregnant uterus toward end of gestation
Causes birth of baby
Oxytocin
Oxytocin on breast milk secretion
Suckling stimulus leads to nerve signals to oxytocin neuron
Release of oxytocin from hypothalamus to posterior
Oxytocin is carried by blood to breast causing contraction of myoepithelial cell outside of alveoli of mammary
Milk let down
