Human physiology part 6

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Human physiology part 6

  1. 1. Principles of Hormonal Control Systems (Part 6)<br />Chapter 10 John Paul L. Oliveros, MD, DPPS<br />
  2. 2. Summary of Hormones<br />
  3. 3.
  4. 4. Hormone structure and synthesis<br />3 chemical classes of hormones<br />Amines<br />Peptides and proteins<br />steroids<br />Amine Hormones<br />Derivatives of tyrosine<br />Include:<br />Thyroid hormones<br />Epinephrine<br />Norepinephrine<br />dompamine<br />Thyroid Hormones<br />Thyroxine (T4) and Triiodothyronine<br />Secreted by thyroid follicles<br />Iodine<br />Essential element of thyroid hormones<br />Food  GI tract  blood (converted to iodide)  thyroid follicular cells (conversion back to iodine)  thyroglobulin (incorportation with tyrosine and thyroglobulin precursor) <br />Thyroglobulin<br />Found in central spaces between thyroid follicles<br />Endocytosis into follicular cells and digested by lysosymes to release thyroid hormones<br />
  5. 5. Thyroid Hormones<br />Thyroxine (T4)<br />Secreted in large amounts<br />Converted into T3 by most tissue by deiodination<br />Has no action unless converted to T3<br />Persons with defective deiodination enzyme manifest as thyroid hormone deficiencyeven with normal or increased T4<br />Triiodothyroxine (T3)<br />More active than T4<br />Function:<br />Regulation of O2 consumption<br />Growth<br />Brain development and function<br />
  6. 6. Adrenal Medulla Glands and Dopamine<br />Adrenal gland<br />Adrenal cortex<br />Adrenal medulla<br />Modified sympathetic ganglion<br />Axons release secretions into blood (endocrine)<br />Secrete 2 amine hormones<br />Epinephrine (E)<br />Secreted 4x more than NE<br />Norepinephrine (NE)<br />Dopamine<br />Secreted by cells in the hypothalamus<br />Function as a hormone<br />Also secreted by small amounts in the adrenal glands<br />
  7. 7. Peptide Hormones<br />Composes majority of hormones<br />preprohormones (ribosomes) prohormones (endoplasmic reticulum)  hormones + peptides (golgi apparatus)<br />Many also functions as neurotransmitters/ neuromodulators<br />
  8. 8. Steroid Hormones<br />Produced by the adrenal cortex and gonads, placenta<br />Cholesterol<br />Steroid produced on a particular cell depends on the types and concentration of enzymes present<br />Highly soluble<br />Steroid producing cell  plasma membrane  interstital fluid blood  binding with plasma proteins<br />
  9. 9. Hormones of the adrenal cortex<br />Aldosterone<br />Mineralocorticoid<br />Salt (mineral) balance<br />Kidney’s handling of Na+, K+, H+ ions<br />Cortisol and Corticosterone<br />Glucocorticosteroid<br />Metabolism of glucose and other organic nutrients<br />Facilitation of response to stress<br />Regulation of immune system<br />Dehydroepiandrosterone (DHEAS) and Androstenedione<br />Androgens<br />Include testosterone (testes)<br />Other adrenal androgens function like testosterone but less potent<br />Play important role in adult female and both sexes during puberty<br />
  10. 10. Hormones of the adrenal cortex<br />3 distinct layers of adrenal cortex<br />Zona glomerulosa<br />High enzyme concentration to convert corticosterone to aldosterone<br />Zona fasciculata<br />Zona reticularis<br />Secretes more androgen and cortisol<br />If less enzyme for conversion to cortisol, may produce masculinzation in females<br />
  11. 11. Hormones of the Gonads<br />High concentrations of enzymes to lead to androstenedione<br />Testes<br />Androstenedione  testosterone<br />Ovaries<br />High concentrations of aromatase <br />Androgens  estradiol<br />Some ovarian cells screte progesterone<br />
  12. 12. Hormone transport in blood<br />Concentration of free hormone is more physiologically important than total concentration<br />
  13. 13. Hormone Metabolism and Excretion<br />Liver and kidneys<br />Major organs for hormone excretion and metabolism<br />Target cells<br />May metabolize cetain peptide hormones<br />Plasma/blood<br />Rapid elimination of peptide hormones and catecholamines<br />Less rapid elimination of protein bound hormones (thyroid and steroid hormones)<br />Metabolism may activate some hormones instead of inactivating them<br />
  14. 14. Mechanisms of Hormone action<br />

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