PHSL 3051 Lecture Notes - Lecture 24: Chemical Substance, Estrone, Insulin
Document Summary
System of organs, cells, and tissues that secrete hormones. Hormone: chemical substance that is secreted into the blood by one cell or group of cells (gland), and has a physiologic control effect on other cells of the body through a specific receptor. Examples: oxytocin, tsh (thyroid stimulating hormone), testosterone (steroid), estrogen. Influence cells by receptors on the target cells. Potent in small concentrations body does not make much. One hormone binds to receptor and many molecules are produced in the cell. Work through receptors that are specific for certain classes of hormones. Ex: estrogen receptors bid estrogens like estradiol, estriol, or estrone. Carried in blood by protein and shielded from being broken down right away. Signal for synthesis automatically leads to secretion. Since they are lipid soluble, they must have a carrier protein. Only free hormone can diffuse into the liver to be broken down. Increased lipid solubility greater binding more shielding longer half-life.
