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Endocrine System and Hormone Physiology - Anatomy & Physiology

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  • Pineal gland function
    Produces serotonin by day and converts it to melatonin at night to regulate circadian rhythm and may regulate timing of puberty.
  • Thymus gland role
    Located in mediastinum, shrinks after puberty, secretes hormones that regulate T-cell development.
  • Parathyroid hormone (PTH) effect
    Released in response to low blood Ca2+ levels and increases Ca2+ concentration in blood.
  • Pancreas endocrine vs exocrine function
    2% of pancreas (islets) produce hormones; 98% produce digestive enzymes (exocrine).
  • Insulin secretion and function
    Secreted by beta cells after meals with carbs/protein; stimulates glucose and amino acid uptake; antagonizes glucagon.
  • Glucagon secretion and function
    Secreted by alpha cells during fasting or low-carb diets; stimulates glycogen breakdown and fat catabolism; antagonizes insulin.
  • Signs of diabetes mellitus
    Polyuria, polydipsia, polyphagia, hyperglycemia, glycosuria, ketonuria, and osmotic diuresis.
  • Type I diabetes mellitus characteristics
    Autoimmune destruction of beta cells, usually diagnosed around age 12, requires insulin injections.
  • Type II diabetes mellitus characteristics
    Insulin resistance with failure of target cells to respond; risk factors include heredity, age 40+, and obesity.
  • Long-term diabetes complications
    Vascular damage causing heart and kidney disease, retinal damage (blindness), poor wound healing, and limb amputations.
  • Hyperinsulinism causes and symptoms
    Caused by excess insulin injection or islet tumor; causes hypoglycemia, weakness, hunger, anxiety, sweating, and increased heart rate.
  • Gestational diabetes
    Occurs during pregnancy due to placental hormones deactivating insulin receptors; reverses after birth but increases type II diabetes risk.
  • Gonadal hormone functions
    Ovaries secrete estrogens and progesterone for female development and pregnancy; testes produce androgens for male development and sperm production.
  • Atrial natriuretic peptide (ANP) role
    Released with increased blood pressure; decreases blood volume and blood pressure.
  • Hormone chemical nature
    Most hormones are protein-based (water-soluble); steroid hormones are lipid-soluble.
  • Lipid-soluble hormone mode of action
    Penetrate plasma membrane, enter nucleus, bind DNA, initiate mRNA transcription, and stimulate protein synthesis.
  • Water-soluble hormone mode of action
    Bind to cell-surface receptors and activate second messenger systems inside the cell.
  • Hormone clearance mechanisms
    Hormones are degraded by liver and kidney, excreted in bile or urine; half-life is time to clear 50% of hormone.
  • Modulation of target cell sensitivity
    Target cells can up-regulate or down-regulate receptor density to increase or decrease hormone sensitivity.
  • General Adaptation Syndrome stages
    Three stages: alarm reaction, resistance, and exhaustion in response to stress.
  • Paracrine secretions
    Chemical messengers that act locally on nearby cells, not transported in blood, e.g., histamine, nitric oxide, eicosanoids.
  • Eicosanoids functions
    Mediate allergic and inflammatory reactions, stimulate vasoconstriction and clotting, mediate smooth muscle contraction, and sensitize neurons to pain.