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