The Endocrine System

• What is the primary function of homeostatic mechanisms in organisms?

  To keep internal body conditions near constant
• What are the three key homeostatic mechanisms?

  • Thermoregulation: control of body temperature
  • Osmoregulation: control of the water potential of body fluids
  • Control of blood glucose concentration
• Why is information transfer important in homeostatic mechanisms?

  It allows different parts of the body to coordinate responses to maintain homeostasis
• What is a hormone?


  A chemical messenger produced by an endocrine gland and carried by the blood
• How do hormones affect target organs?

  They alter the activity of one or more specific target organs
• What type of functions do hormones control?

  Functions that do not need instant responses
• What is a gland?

  A group of cells that produces and releases one or more substances
• What hormone does the thyroid gland produce?

  Thyroxine
• What is the role of the pituitary gland?


  It is known as the master gland
• What hormone does the pancreas produce?

  Insulin
• What hormone do the testes produce?

  Testosterone
• What hormone do the adrenal glands produce?


  Adrenaline
• What hormones do the ovaries produce?

  Estrogen
• How do endocrine glands function in the body?

  • They have a good blood supply
  • They secrete hormones directly into the bloodstream
  • Hormones are transported to target cells/tissues
• Why do hormones only affect certain cells in the body?

  Because only target cells have receptors that the hormone can bind to
• Where are hormone receptors typically found?

  On the cell surface membrane
• What is required for a hormone to have an effect on a cell?

  The receptor must be complementary to the hormone
• What is the process of hormone action involving first and second messengers?

  • First messenger: the hormone that brings the signal from the endocrine gland
  • Hormones bind to receptors on the cell surface membrane
  • Second messenger: causes the effect inside the cell
• How does adrenaline function as a first messenger?

  It binds to a receptor on the cell surface membrane
• What is the role of cyclic AMP in hormone action?

  It acts as a second messenger causing an effect in the cell
• What are the key differences between the nervous system and the endocrine system?

  • Nervous system: electrical impulses, fast transmission, targets muscles or glands
  • Endocrine system: chemical hormones, slower transmission, targets specific tissues