BIOLOGY 20 Lecture Notes - Lecture 28: Calcium Metabolism, Dehydroepiandrosterone, Keratinocyte
Document Summary
Keratinocytes convert a cholesterol like steroid into cholecalciferol (vitamin d) using uv from sun. Liver involved in the production of hormones. Secretes 15% of erythropoietin (stimulates bone marrow) Hepcidin promotes intestinal absorption of iron. Kidneys plays a role in production of three hormones. Converts calcidiol to calcitriol, the active form of vitamin d increases ca2+ absorption by intestine and inhibits loss in the urine. Secrete renin that converts angiotensinogen to angiotensin ! Most cells sensitive to more than one hormone and exhibit interactive effects of hormones. When both are present, observed effects are weaker than those produced by either hormone unopposed. One hormone is needed for 2nd to produce its effect. Example: epinephrine changes rate of cellular energy consumption only in presence of thyroid hormones. Net result from two hormones is greater than each acting alone, often greater than the sum. Example: the combination of sex hormones and hgh causes more rapid growth than either sex hormone or hgh alone.
