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