Human Physiology

• Organ systems


  • Muscular system
  • Cardiovascular system
  • Respiratory system
  • Digestive system
  • Nervous system
  • Endocrine system
  • Urinary system
• All organ systems are connected
• Negative feedback loop


  Most homeostatic responses are maintained via this
• Positive feedback loop

  • Occurs in special situations such as blood clotting
  • Can shift homeostatic set point to a new level
  • Example: during childbirth - oxytocin release causes contractions to become more frequent and more powerful and therefore causes more oxytocin to be released until the baby is born
• As we age


  Our body's control systems become less efficient and our internal environment becomes less stable, therefore increase risk for illness and produce the changes we associate with aging
• Negative feedback mechanisms are overwhelmed

  Destructive positive feedback mechanisms take over
• Changes in the external environment


  Can displace a variable from its set point and many regulated variables can be physiologically reset to a new value
• The homeostatic control systems regulating body temperature are functioning during a fever but they maintain the temperature at an increased value which is needed to fight the infection
• The set point for body temperature is higher during the day than at night