Epinephrine Receptor Phospholipase c protein membrane CONbEOnOtOmloonn Endoplasmic G prot pr Calmodulin reticulum Hormone effects ⑤◎ FIGURE 53. 8 The IPy/Ca" second-messenger system. (I) The hormone epinephrine binds to specific receptor proteins on the cell surface. (2) cting through G proteins, the hormone-bound receptor activates the enzyme phospholipase C, which converts membrane phospholipids into inositol trisphosphate (IPo).(3) IP diffuses through the cytoplasm and binds to receptors on the endoplasmic reticulum. (+)The binding of IP, to its receptors stimulates the endoplasmic reticulum to release Ca into the cytoplasm. () Some of the released Ca" binds to a regulatory protein called calmodulin (6)The Ca"/calmodulin complex activates other intracellular proteins, ultimately producing the ffects of the hormone
Introduction Vesicle containing first messenger Endocrine land cell Peptide hormone bloodstream Cell membrane Blood vessel cyclase Cell division O +growth G pro signal Secretion(4s receIves Increased signal cardiac muscle AMP contraction Most vertebrate hormones are peptides. They bind to cells with the appropriate membrane receptors. This causes the conversion of ATP to cyclic AMP. Cyclic AMP [cAMP acts as a second messenger and activates specific enzymes in the target cell
分泌系统 类固醇激素作用机制基因调节学说 类固醇激素分子小,具脂溶性,可透过细胞膜进入靶细胞—和胞浆 受体结合形成激素胞浆受体复合物透过核膜与核内受体结合成 为激素核受体复合物一激动DNA的转录过程,促进mRNA的形成 诱导生成新蛋白质发挥生理效应
2. 类固醇激素作用机制——基因调节学说 类固醇激素分子小，具脂溶性，可透过细胞膜进入靶细胞 和胞浆 受体结合形成激素—胞浆受体复合物 透过核膜与核内受体结合成 为激素—核受体复合物 激动DNA的转录过程，促进mRNA的形成 诱导生成新蛋白质 发挥生理效应。 第八节 动物内分泌系统
CHa CH. OH CH CH CH3 CH CH。CH CH CH CH HO HO Estradiol-17B Cholesterol CH2OH OH C=O CH CH HO -OH CH CH Testosterone Cortisol(hydrocortisone FIGURE 53.4 Chemical structures of some steroid hormones. Steroid hormones are derived from the blood lipid cholesterol. The hormones shown, estradiol, testosterone, and cortisol differ only slightly in chemical structure yet have widely different effects on the body Steroid hormones are secreted by the testes, ovaries, and placenta
ero Blood plasma Plasma membrane Cytoplasm ① Steroid hormone(S) passes through plasma membrane (2 Inside target cell, steroid hormone binds to a specific receptor protein in cytoplasm or nucleus (3 Receptor/steroid hormone complex enters the nucleus and binds to DNA, causing gene transcription. 4 Protein synthesis is induced 5 Protein is produced Chromosome mRNA Nucleus FIGURE 53.5 The mechanism of steroid hormone action. Steroid hormones are lipid-soluble and thus readily diffuse through the plasma membrane of cells. They bind to receptor proteins in either the cytoplasm or nucleus (not shown). If the steroid binds to a receptor in the cytoplasm. the steroid/receptor complex moves into the nucleus. The steroid/receptor complex then binds to specific regions of the DNA stimulating the production of messenger RNA (mRNA