Endocrine System

• Regulation
  • Why are hormones needed?
  • Chemical messages from one body part to another
  • Communication needed to coordinate whole body
  • Daily homeostasis and regulation of large scale changes
    • Solute levels in blood
    • Glucose
    • Ca2+
    • Salts
    • Metabolism
    • Growth
    • Development
    • Maturation
    • Reproduction
• Regulation and Communication
  • Animals rely on 2 systems for regulation
  • Endocrine system
    • System on ductless glands
    • Secrete chemical signals directly into blood
    • Chemical travels to target tissue
    • Target cells have receptor proteins
    • Slow, long-lasting response
  • Nervous system
    • System of neurons
    • Transmits “electrical” signal and release neurotransmitters to target tissue
    • Fast, short-lasting response
• Regulation by chemical messengers
  • Neurotransmitters released by neurons
  • Hormones release by endocrine glands
• Classes of Hormones
  • Protein based hormones
  • Polypeptides
    • Small proteins
    • Insulin
    • ADH
  • Glycoproteins
    • Large proteins and carbohydrates
    • FSH
    • LH
  • Amines
    • Modified amino acids
    • Epinephrine
    • Melatonin
  • Lipid based hormones
  • Steroids
    • Modified cholesterol
    • Sex hormones
    • Aldosterone
• How do hormones act on target cells
  • Lipid based hormones
  • Hydrophobic and lipid-soluble
    • Diffuse across cell membrane and enter cells
    • Bind to receptor proteins in cytoplasm and nucleus
    • Bind to DNA as transcription factors
    • Turn on genes
  • Protein based hormones
  • Hydrophilic and not lipid soluble
    • Can’t diffuse across cell membrane
    • Bind to receptor proteins in cell membrane
    • Trigger secondary messenger pathway
    • Activate internal cellular response
    • Enzyme action, uptake or secretion of molecules
• Nervous and Endocrine Systems Linked
  • Hypothalamus = master nerve control center
  • Nervous system
  • Receives information from nerves around body about internal conditions
  • Releasing hormones
    • Regulates release of hormones from pituitary gland
  • Pituitary gland = master gland
  • Endocrine system
  • Secretes broad range of “tropic” hormones regulating other glands in body
• Regulating Metabolism
  • Hypothalamus
  • TRH
    • TSH - releasing hormone
  • Anterior Pituitary
  • TSH
    • Thyroid-stimulating hormone
  • Thyroid
  • Produces thyroxine hormones
  • Metabolism and development
    • Bone growth
    • Mental development
    • Metabolic use of energy
    • Blood pressure and heart rate
    • Muscle tone
    • Digestion
    • Reproduction
• Goiter
  • Iodine deficiency causes the thyroid to enlarge as it tries to produce thyroxine

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