Endocrine system

• Endocrine system


  A body control system composed of a group of glands that maintain a stable condition within the body's internal environment by producing chemical regulatory substances into the bloodstream called hormones

  
• Hormones


  Chemical messengers secreted by endocrine glands and transported to target cells in the bloodstream

  
• Hormones


  • Each target cell contains receptor proteins; it receives and responds to the chemical message sent by the hormone

  
• Steroid hormones


  Act on intracellular nuclear proteins, H-R complex acts as ligan dependent transcription factor to activate/inhibit transcription of specific genes

  
• Non-steroid hormones


  Act on cell surface receptors, H-R complex leads to the generation of second messenger within the cell, which triggers a series of molecular interactions that alter the physiological state of the cell (signal transduction)

  
• Pituitary gland


  1. Posterior pituitary produces oxytocin and antidiuretic hormone (ADH)

  2. Anterior pituitary produces thyroid-stimulating hormone (TSH), growth hormone (GH), adrenocorticotropin (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin

  
• Thyroid gland


  Produces thyroxine (T4), triiodothyronine (T3), calcitonin

  
• Parathyroid glands


  Produce parathyroid hormone (PTH) to increase blood calcium level and decrease blood phosphate ion concentration
• Pancreas


  Has both endocrine and exocrine functions, secretes digestive enzymes and hormones like insulin and glucagon

  
• Adrenal glands


  Adrenal medulla secretes catecholamine hormones noradrenaline and adrenaline, adrenal cortex secretes glucocorticoids, mineralocorticoids, and androgenic hormones

  
• Gonads


  Ovaries produce estrogen and progesterone, testes produce testosterone
• Pineal gland


  Secretes melatonin in response to light, regulates sleep patterns and assists in regulation of female reproductive cycle
• Endocrine glands and their hormones

  • Posterior Pituitary: ADH, Oxytocin
  • Anterior Pituitary: TSH, GH, ACTH, FSH, LH, Prolactin
  • Thyroid: Thyroxine, Triiodothyronine, Calcitonin
  • Parathyroid: PTH
  • Pancreas: Insulin, Glucagon, Somatostatin
  • Adrenal Medulla: Adrenaline, Noradrenaline
  • Adrenal Cortex: Glucocorticoids, Mineralocorticoids, Androgenic hormones
  • Testes: Testosterone
  • Ovaries: Estrogen, Progesterone
  • Pineal: Melatonin

  
• Regulation of the endocrine system


  • Humoral, Neural, Hormonal
  • Hypothalamus-pituitary hormone axes
  • Feedback control
  • Cycles of secretion
  • Antagonistic pairs of hormones

  
• After eating, a person's blood glucose level increases
• The pancreas secretes insulin and glucagon
• Insulin lowers glucose levels
• Glucagon raises glucose levels
• Glucose feedback loop


  1. Increase in blood glucose level

  2. Pancreas secretes insulin

  3. Insulin lowers blood glucose level

  4. Decrease in blood glucose level

  5. Pancreas secretes glucagon

  6. Glucagon raises blood glucose level