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Oxytocin produced by
hypothalamus nerve signal stimulates paraventricular nuclei in posterior pituitary to produce and release
stimulates labor contractions in uterus and milk ejection in mammary glands during suckling.
Antidiuretic hormone (ADH) produced by
hypothalamus nerve signal stimulates supra optic nuclei in posterior pituitary to produce and release
Antidiuretic hormone (ADH) action
promotes water retention to raise blood pressure, AKA vasopressin
-In presence of ADH, permeability of collecting ducts increases, allowing water to be reabsorbed (conc. urine)
-Acts via adenyl cyclase-cAMP 2nd messenger system
Antidiuretic hormone (ADH) mechanism of control
-When stretch receptors in the atrial vessles stretch (due to high BP), signal is sent to the brain to inhibit ADH secretion
Thyroxine (T4) & Triiodothyronine (T3) action
increases metabolic rate (glucose oxidized, heat generated etc.)
stimulates calcium phosphate disposition and bone tissue "to reduce blood calcium levels"
Parathyroid hormone (PTH) action
stimulates osteoclast resorption of bone to released calcium and calcium absorption by kidneys and intestines
increases energy supplies; controls stress; controls metabolism of proteins, carbohydrates, and fats; anti-inflammatory effects
Atrial natriuretic peptide action
inhibits release of aldosterone, reduces the blood volume/pressure (tells kidneys to secrete salty urine)
Gastrin, secretin, cholecycstokinin action
stimulate HCG secretion, GI tracked mobility, release of bicarbonate rich juices, expulsion of bile, etc.
Growth hormone releasing hormone (GHRH) action
stimulates growth hormone production
-Short-term: mediated by increased Ca
-Long-term: increases transcription in the nucleus by genes
Gonadotropin releasing hormone (GnRH) action
stimulates follicle stimulating hormone and luteinizing hormone
Growth Hormone (Somatotropin) action
Works via somatomedins such as IGF-1 (somatomedin C) to:
-Somatomedins attach more strongly to carrier protein then does GH, giving it a prolonged action.
-Stimulates protein synthesis
-mobilization of fatty acids for energy
-decreased glc utilization
-promotes protein deposition
-reduces insulin's actions
-overall growth of most cells and tissues (no specific tissue or gland)
Growth Hormone (Somatotropin) mechanism of control
-Stimulated in a pulsatile pattern due to many diff. factors (Starvation, hypoglycemia, exercise, deep sleep, GHRH)
-Inhibited by many diff. factors (GHIH or somatostatin, aging, increased bld glc, increased free fatty acids in bld, exogenous GH, somatomedins)
Growth Hormone (Somatotropin) abnormalities
Panhypopituitarism: decreased secretion of all anterior pituitary hormones==> Dwarfism if in childhood, or loss of sexual function/weight gain if in adulthood
Dwarfism: results from generalized deficiency of anterior pituitary secretion during childhood (body parts develop proportionally but at a much slower rate)
Gigantism: Hormone producing cells excessively active during adolescence. All body tissues grow larger, including bones.
Acromegaly: Excessively active GH producing cells after adolescence (after epiphysesial growth plate closure). Bones become thicker and soft tissue becomes larger.
Thyroid-Stimulating Hormone (TSH) action
Stimulates synthesis and secretion of thyroid hormones (T4 & T3)
Thyroid-Stimulating Hormone (TSH) mechanism of control
-Stimulated by low T3
-Inhibited by high T4 or T3
Adrendocorticotropic Hormone (ACTH) action
Stimulates synthesis and secretion of adrenocortical hormones (cortisol, androgens, and aldosterone)
Follicle-Stimulating Hormone (FSH) action
Causes growth of follicles in the ovaries and sperm maturation in Sertoli cells of the testes
-Controls their hormonal and reproductive activities
Luteinizing Hormone (LH) action
Stimulates testosterone synthesis in Leydig cells of testes
Stimulates ovulation, formation of corpus luteum, and estrogen and progesterone synthesis in ovaries
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