tortora endocrine

• Puberty


  • Girls and boys start to develop striking differences in physical appearance and behavior
  • The endocrine system directs development and regulates body functions
• Estrogens


  Promote accumulation of adipose tissue in the breasts and hips, sculpting a feminine shape
• Testosterone


  Helps build muscle mass and enlarge the vocal cords, producing a lower-pitched voice
• Hormones help maintain homeostasis on a daily basis
• Hormones regulate the activity of smooth muscle, cardiac muscle, and some glands
• Hormones alter metabolism
• Hormones spur growth and development
• Hormones influence reproductive processes
• Hormones participate in circadian (daily) rhythms established by the suprachiasmatic nucleus of the hypothalamus
• Exocrine glands


  Secrete their products into ducts that carry the secretions into body cavities, into the lumen of an organ, or to the outer surface of the body
• Endocrine glands


  Secrete their products (hormones) into the interstitial fluid surrounding the secretory cells rather than into ducts
• Endocrine glands


  • Pituitary
  • Thyroid
  • Parathyroid
  • Adrenal
  • Pineal
• Other organs and tissues that contain hormone-secreting cells

  • Hypothalamus
  • Thymus
  • Pancreas
  • Ovaries
  • Testes
  • Kidneys
  • Stomach
  • Liver
  • Small intestine
  • Skin
  • Heart
  • Adipose tissue
  • Placenta
• Endocrine system


  All endocrine glands and hormone-secreting cells
• Endocrinology is the science of the structure and function of the endocrine glands and the diagnosis and treatment of disorders of the endocrine system
• Organs/tissues that contain cells that secrete hormones but are not exclusively endocrine glands

  • Hypothalamus
  • Thymus
  • Pancreas
• Hormone


  A molecule that is released in one part of the body but regulates the activity of cells in other parts of the body
• Hormone receptors


  Specific protein receptors on target cells that bind and recognize a particular hormone
• Down-regulation


  Decrease in the number of hormone receptors on a target cell when exposed to high hormone concentrations, making the cell less sensitive to the hormone
• Up-regulation


  Increase in the number of hormone receptors on a target cell when exposed to low hormone concentrations, making the cell more sensitive to the hormone
• Circulating hormones


  Hormones that pass from secretory cells into interstitial fluid and then into the bloodstream
• Local hormones


  Hormones that act locally on neighboring cells (paracrines) or on the same cell that secreted them (autocrines) without entering the bloodstream
• Local hormones


  • Interleukin-2
  • Nitric oxide
• Lipid-soluble hormones


  Include steroid hormones, thyroid hormones, and nitric oxide
• Water-soluble hormones


  Include amine hormones, peptide and protein hormones, and eicosanoid hormones
• Steroid hormones


  Derived from cholesterol, with unique chemical groups attached to the four-ring core structure
• Thyroid hormones (T3 and T4)

  Synthesized by attaching iodine to the amino acid tyrosine
• Amine hormones


  Synthesized by decarboxylating and otherwise modifying certain amino acids, retaining an amino group (NH3+)
• Peptide and protein hormones

  Amino acid polymers, with peptide hormones consisting of 3-49 amino acids and protein hormones consisting of 50-200 amino acids
• Lipid-soluble


  Makes molecules very soluble in lipids (see Table 18.2)
• Nitric oxide (NO)


  A gas that is both a hormone and a neurotransmitter, its synthesis is catalyzed by the enzyme nitric oxide synthase
• Water-soluble hormones


  • Amine hormones
  • Peptide and protein hormones
  • Eicosanoid hormones
• Amine hormones


  Synthesized by decarboxylating and otherwise modifying certain amino acids, retain an amino group (NH3+)
• Peptide hormones and protein hormones

  Amino acid polymers, smaller peptide hormones consist of 3 to 49 amino acids, larger protein hormones include 50 to 200 amino acids
• Eicosanoid hormones


  Derived from arachidonic acid, a 20-carbon fatty acid, include prostaglandins and leukotrienes
• Eicosanoids are important local hormones, and they may act as circulating hormones as well
• Table 18.2 summarizes the classes of lipid-soluble and water-soluble hormones and provides an overview of the major hormones and their sites of secretion
• Hormone transport in the blood

  Most water-soluble hormones circulate in the watery blood plasma in a "free" form, but most lipid-soluble hormones are bound to transport proteins
• Functions of transport proteins

  • Make lipid-soluble hormones temporarily water-soluble
  • Retard passage of small hormone molecules through the filtering mechanism in the kidneys
  • Provide a ready reserve of hormone, already present in the bloodstream
• 0.1–10% of the molecules of a lipid-soluble hormone are not bound to a transport protein, this free fraction diffuses out of capillaries, binds to receptors, and triggers responses</b>