Human physiology part 6
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Human physiology part 6

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Human physiology part 6 Human physiology part 6 Presentation Transcript

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