Chapter 12

• Homeostasis


  The process of maintaining a stable internal environment in the body
• Temperature control


  1. Receptors in hypothalamus detect temperature change

  2. Receptors in skin detect temperature change

  3. Body issues response (shivering, vasoconstriction, sweating, vasodilation)
• Vasoconstriction


  Pulls blood away from skin surface, reduces heat loss
• Hypothermia


  Caused by prolonged vasoconstriction, not enough blood to vital areas
• Sweating


  Cools body as sweat evaporates
• Vasodilation


  Expands arteries, allows more heat to leave body
• Heat stroke


  Caused by prolonged sweating and water loss
• Waste products


  Carbon dioxide (from respiration), urea (from amino acid breakdown)
• Kidney function


  1. Blood enters via renal artery

  2. Blood filtered, useful substances reabsorbed

  3. Waste (urea, excess minerals) excreted as urine

  4. Urine exits via renal vein
• ADH


  Hormone that regulates water reabsorption by kidneys
• Alcohol consumption


  Increases ADH production, leading to dehydration
• Kidneys filter all blood in body around 40 times per day
• Kidney failure


  • Minerals not reabsorbed properly
  • Causes fatigue and illness
• Kidney dialysis


  1. Blood filtered externally by machine

  2. Machine adjusts mineral levels as needed

  3. Blood returned to body
• Kidney dialysis


  • Long process, requires controlled diet
• Artificial kidney


  Kidney transplant, but risk of rejection