endocrine

• Endocrine system


  A system made up of glands responsible for making and secreting hormones. Works to regulate bodily functions and maintain homeostasis.
• Endocrine system


  • Receives signals from the nervous system
  • Releases hormones into the blood stream
• Main functions of the endocrine system

  • Osmoregulation (water levels)
  • Blood glucose levels
  • Overall rate of metabolism
  • Adrenaline response
  • Sexual development
  • Growth and development
  • Emotions
• Hypothalamus


  Section of the brain that connects the nervous system and endocrine system. Communicates with the pituitary gland to initiate hormone production.
• Pituitary gland


  Master gland. Receives information from the hypothalamus and instructs other glands on what to do. Produces and releases anti-diuretic hormone (ADH) and thyroid stimulating hormone (TSH).
• Thyroid gland


  Produces and releases thyroxine, regulates metabolism.
• Adrenal gland


  Produces and releases adrenaline, a hormone involved in flight/fight/freeze response.
• Pancreas


  Alpha-cells produce and release glucagon which acts to raise blood glucose levels. Beta-cells produce and release insulin, which acts to lower blood glucose levels.
• Ovaries/Testes


  Produce and release oestrogen and testosterone, which are involved in growth, development and reproduction.
• Hormones


  Chemical messengers released by cells of endocrine glands that travel to target cells in the blood stream to stimulate a response.
• Hormones


  • Involved in negative feedback to stimulate a response
  • Can act on any cell in the body that contains an appropriate receptor
  • Can be composed of peptides, proteins, or steroids
• Steroid hormone transduction


  Steroid hormones are hydrophobic and lipid soluble, so they can diffuse through the phospholipid bilayer and bind to a receptor inside the cells.
• Protein and peptide hormone signal transduction

  Protein and peptide hormones are hydrophilic and not lipid soluble, so they cannot diffuse through the cell membrane. They bind to receptors on the surface of the cell membrane.
• Homeostasis


  Allows the body's internal environment to remain relatively constant despite internal and external environmental factors.
• Homeostatic processes


  • Blood glucose levels
  • Temperature
  • Water balance
• Stimulus response model


  Allowing the body to respond appropriately to internal or external changes in its environment. When a stimulus is detected, a bodily response is initiated to return the body back to homeostasis.
• Negative feedback


  Feedback loops that decrease the magnitude of a process in response to the feedback from the end product.
• Negative feedback loops


  • Blood-glucose levels
  • Thermoregulation (temperature regulation)
  • Osmoregulation (water balance)
• If blood glucose levels go too high

  Negative feedback will bring them back down to normal levels
• If blood glucose levels decrease too much

  Negative feedback will bring them back up to normal levels
• Positive feedback


  Feedback loops that increase the magnitude of a process in response to its end product.
• Positive feedback loop


  • Stretching of the cervix during child birth causes the release of oxytocin and uterine contractions. The contractions then cause further stretching, oxytocin release and additional contractions, effectively feeding back to the beginning of the process.