enrinology內(nèi)分泌總論-wenkub
2023-05-25 01:40:49 本頁(yè)面
【正文】 ormones are customarily divided into three groups: ? Proteins and peptides: insulin （蛋白質(zhì)和肽類(lèi)激素） ? Steroids: cortisol （類(lèi)固醇激素） ? Amino acid analogues: T3, T4 （氨基酸類(lèi)激素） Steroids ? Tissues which produce steroid hormones include ovary/testis, adrenal cortex, placenta and skin(vitamin D). ? All steroid hormones are based on the precursor molecule cholesterol. Regulation of hormone levels ? Spontaneous, or basal, hormone release ? Feedback inhibition by hormones of their synthesis and/or release ? Stimulation or inhibition of hormone release by substances that may or may not be regulated by the same hormones ? Establishment of circadian rhythms for hormone release by systems such as the brain ? Brain mediated stimulation or inhibition of hormone release in response to anxiety anticipation of a specific activity, or other sensory inputs. Hypothalamuspituitaryadrenal axis ? The hypothalamus produces CRH, which travels down the portal vessels through the hypothalamic stalk to the anterior pituitary, where it stimulates ACTH release. ? ACTH then travels to the adrenal gland, where it stimulates the release of cortisol. ? Cortisol in turn inhibits both CRH and ACTH release（ feedback inhibition） . ? The brain establishes circadian rhythms and can trigger increased CRH release in response to stress. CRH ACTH cortisol Mechanisms of hormone action ? Peptide and catecholamine hormones and prostaglandins bind to receptors on the cell surface. ? Steroid and thyroid hormones act for the most part by binding to intracellular receptors. ? binding to receptors on the cell surface ? binding to intracellular receptors hormones bind to receptors on the cell surface ? Peptide and catecholamine hormones and prostaglandins bind to receptors on the cell surface, where the hormonereceptor interactions affect intracellular mediators, or second messengers. Second messengers ? cAMP: ? Glucagon, ACTH, PTH ? Protein kinase activity ? Insulin ? Calcium ? Alphaadrenergic agonists, AT II ? phospholipids ? ADH, GnRH, TRH. hormones bind to receptors on the cell surface binding to intracellular receptors intracellular rece
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