Endocrine System Lecture
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sq2therescq on October 25, 2011
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58 terms
Terms | Definitions |
|---|---|
 Autocrine Secretion | Cell secretes a chemical messenger to act on its own receptors |
| Paracrine Secretion | Cell secretes a chemical messenger to act on receptors of ADJACENT cells |
| Endocrine Secretion | Cell secretes a chemical messenger (hormone) into the blood stream to act on DISTANT cells |
| Synaptic Communication | By direct structural targeting from one cell to another via synapses |
| Hormones | Chemical messengers that are carried via the blood stream to distant target cells. There are two types of hormones that differ based on how the enter cell membrane. |
| Water Soluble Hormones | Interact with specific cell-surface receptors on target cells, which communicate a message that generates a biological response by the cell. Polypeptides and low molecular weight proteins (e.g. insulin, glucagon, follicle-stimulating hormone) |
| Lipid Soluble Hormones | Diffuse directly across the plasma membrane of target cells and receptor will usually be in the cytosol or nucleus. These hormone-receptor complexes enter the nucleus to regulate transcription of DNA Principally steroid hormones (e.g. progesterone, estradiol, testosterone) |
| G-Protein Linked Receptors (Water-Soluble Hormones) | Binding of hormone to G-protein-linked receptor leads to production of a second messenger that evokes a target cell response |
| Catalytic Receptors (Water-Soluble Hormones) | Utilized by insulin and growth hormone. Binding activates protein kinases that phosphorylate target proteins |
| Hypothalamus | Coordination between the endocrine and nervous systems. Several clusters of neurons in the brain secrete hormones which act as releasing or inhibiting factors. These hormones are transported to pituitary via two routes |
| Hormone Route: Hypothalamus -> Anterior Pituitary | A specialized system of blood vessels (portal system) transports hypothalamic hormones to act on neuroendocrine cells |
| Hormone Route: Hypothalamus -> Posterior Pituitary | Axons project down from the hypothalamus to form the pituitary stalk that terminates as the posterior pituitary |
| Hormones Secreted by the Hypothalamus | Oxytocin, ADH, TRH, Gonadotropin releasing hormone, Growth hormone releasing hormone, Corticotropin releasing hormone, Somatostatin, Dopamine |
| Oxytocin | Baby suckling stimulates release of oxytocin, which stimulates the release of prolactin by the acidophils in anterior pituitary. It causes release of milk, but not w/o pregnancy first. It also helps get out placenta |
| Dopamine (Prolactin Inhibiting Hormone) | Inhibition of prolactin release from acidophils |
| Hypothalamic Nuclei | The axons of neurons carry hypothalamic hormones to pituitary |
| Supraoptic & Paraventricular Nuclei | These hypothalamic nuclei secrete peptides->axonal transport->posterior pituitary->exocytosis->blood. Axons transports oxytocin, vasopressin, neurophysin (a binding protein specific for each hormone) and ATP to the pars nervosa |
| Dorsal Medial, Ventral Medial, & Infundibular Nuclei | These hypothalamic nuclei secrete peptides->axonal transport->median eminence->storage->released to anterior pituitary via hypophyseal portal vessels |
| Adenohypophysis (Anterior Pituitary) | Subdivided into pars distalis, pars tuberalis & pars intermedia |
| Pars Distalis | Two cell types: acidophils & basophils. Synthesize, store and secrete several hormones. It is regulated by stimulatory and inhibitory hormones produced by the hypothalamus & transported to the pars distalis via portal blood vessels in the median eminence |
| Acidophils | "Make milk that help you grow". Prolactin, GH |
| Basophils | Produces all trophic cells. FSH & LH (gonadotropic), TSH (thyrotropic), ACTH & alphaMSH (corticotropic) |
| Hypothalamic Control of Pars Distalis: Stimulatory | Thyrotropin releasing hormone (TRH), Gonadotropin releasing hormone, Growth hormone releasing hormone, Corticotropin releasing hormone. "Thunder makes Guys Grow Crazy.." |
| Hypothalamic Control of Pars Distalis: Inhibitory | Growth hormone inhibiting hormone (somatostatin) & Prolactin inhibiting hormone (dopamine). "..and Girls Pretty" |
| Somatotropin | Growth Hormone. Increases metabolism in most cells; indirectly stimulates epiphyseal plates and growth of long bones via production of somatomedins in the liver; can cause acromegly, gigantism, dwarfism |
| Thyroid-Stimulating Hormone (TSH) | Stimulates, synthesis and release of thyroid hormones (T3 and T4) by thyroid follicular cells |
| Prolactin | Promotes development of mammary gland during pregnancy; stimulates milk production for lactation |
| Adrenocorticotrophic Hormone (ACTH) | Stimulates synthesis and release of hormones (particularly glucocorticoids) by the adrenal cortex |
| Follicle-Stimulating Hormone (FSH) | Stimulates growth of secondary ovarian follicles & estrogen secretion in women; Stimulates spermatogenesis via production of androgen-binding protein in sertoli cells, located in seminiferous tubules |
| Luteinizing Hormone (LH) | Promotes ovulation, formation of the corpus luteum & progesterone secretion in women; stimulates testosterone synthesis by Leydig cells in the testes (ICSH) |
| Pars Tuberalis | Mostly FSH and LH secreting cells |
| Pars Intermedia | Weakly basophilic cells; alpha-melanocyte-stimulating hormone during FETAL development |
| Neurohypophysis (Posterior Pituitary) | No secretory cells. Two parts: Pars Nervosa & Neural Stalk. 100,000 neurons in the supraoptic and paraventricular nuclei of hypothalamus send axons down the neural stalk to end in the pars nervosa |
| Hormones Stored in Posterior Pituitary | Oxytocin and ADH (vasopressin) |
| Herring bodies | At the end of neuronal axons in the Pars Nervosa; each contains many neurosecretory granules; as granules are released, they reach the blood via surrounding fenestrated capillaries. These contain ADH and Oxytocin |
| ADH (vasopressin) | 1)Prevents water loss in urine. 2) high dose->vasoconstriction->increase BP |
| Pituicytes | Highly branching, glial-like cells that surround, sometimes engulf, the axonal endings |
| Pineal Gland | Responsible for biorhythm; contains calcified material = brain sand; composed primarily of pinealocytes and astrocytes |
| Pinealocytes | cells with long process that end in dilatations near capillaries; synthesize and secrete serotonin (usually during the day) & melatonin (usually at night) |
| Suprarenal (Adrenal) Gland | Paired, adjacent to superior pole of each kidney. 2 separate glands: yellowish cortex (neural crest) & red/brown medulla (coelomic epithelium). Dense fibrous capsule, with septa (trabeculae) going into the gland |
| Adrenal Cortex | Steroid Hormones: Mineralocorticoids (z. glomerulosa), Glucocorticoids (z. fasciculata), Androgen (z. reticularis). Cells do NOT store the hormone-they synthesize and release it on demand. Steroids=lipid soluble=diffuse freely through target cell membrane |
| Zona Glomerulosa (Adrenal Cortex) | Immediately beneath the capsule; pyramidal cells arranged in arching cords; secrete aldosterone |
| Aldosterone | aldosterone-> distal convoluted tubules, salivary & sweat glands, and colon and gastric mucosa ->reabsorption of sodium-> make us more salty! |
| Zona Fascicularis (Adrenal Cortex) | 65% of gland mass; cords are one or two cell thick and run vertical to gland surface; cells are polyhedral with abundant lipid droplets in cytoplasm. Synthesize and secrete corticosteroids |
| Corticosteroids | Corticosteroids->catabolic CHO, protein and lipid metabolism. Cortisons are catabolic- an emergency hormone to break down ANYTHING for glucose to increase glucose level |
| Zona Reticularis (Adrenal Cortex) | Inner most layer; 7 % gland mass; irregular cellular cords; smaller cells with lipofuscin pigment granules; synthesize and secrete a weak androgen (DHEA) |
| DHEA (dehydroepiandrosterone) | DHEA->converted to testosterone in several tissues |
| "All CEOs in America have Good Fat Retirement" | From outside in: Aldosterone -> Glomerulosa Cortisone -> Fasciculata Androgens -> Reticularis |
| Adrenal Medulla | Cells are modified sympathetic postgenglionic neurons that lost their axons and dendrites; arranged in short cords or clumps; abundant membrane bound granules, containing epinephrine or norepinephrine, ATP, chromogranins, dopamine beta-hydorxylase and enkephalins |
| Endocrine Pancreas | Islets of langerhans; acidophils (A cells=glucagon) & basophils (B cells=insulin) |
| Thyroid Gland | Synthesize T3 & T4 (main functions: growth, cell differentiation, basal metabolic rate); only tissue w/ I concentration; follicles have central cavities filled with colloid (large stores of thyroid hormone-3m supply); extensive blod and lymph supply |
| Thyroid Gland Cells | Have central nuclei and have prominent Golgi, rER, and many lysosomes and secretory granules |
| Parafollicular cells-C cells (Thyroid Gland) | Within follicular epithelium or as clusters between follicles; long mitochondria, large golgi and less rER; Secretory granules containing calcitonin |
| Calcitonin | Preserves bone mass by limiting osteoclast-induced bone demineralization -> lower blood calcium level |
| Thyroid Hormone Synthesis | 1)Thyroglobulin synthesis 2)Iodide uptake 3) Iodide oxidation and transport into follicular cavity 4) Iodinization of tyrosine |
| Thyroid Hormone Release | TSH->colloid is taken up by follicular cells->digestion in lysosomes->liberation of T3 & T4 into the cytoplasm; T3 & T4 cross the basolateral membrane into fenestrated capillaries; recycling of tyrosine and iodide |
| Parathyroid Glands | Four small glands located behind the thyroid, one on each corner; cells arranged in cords and have two cell types: chief cells->PTH & oxyphil cells |
| Parathyroid Hormone (PTH) | Binds to receptors on osteoblasts->osteoclast stimulating factor (IL-1) release->demineralization of bone matrix-> +++serum calcium. Also stimulates vitamin D synthesis->more Ca is absorbed in GI tract Also decreases serum phosphates by increasing its excretion in urine |
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