Chemical signals

• Involves glands and hormones
• Gland is group of cells secreting a useful substance
• Hormones are chemical messengers
• Hormones secreted when gland is stimulated
• Hormones diffuse directly into blood then taken around the body
• Hormones diffuse all over but only bind to specific receptors
• Hormones trigger response in target cells
• Stages of endocrine system

  1. Stimulus
  2. Receptors
  3. Hormone
  4. Effectors
  5. Response
• Endocrine system major glands

  • Hypothalamus (Control pituitary gland)
  • Pituitary gland (Control other glands)
  • Pineal gland (Produce melatonin)
  • Adrenal gland (Secrete adrenaline)
  • Pancreas (Release insulin)
  • Thyroid gland (Produce thyroxine)