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