Homeostasis

• Homeostasis


  The process of keeping the internal environment of the body fairly constant
• Factors that need to be kept constant in homeostasis


  • Water
  • Temperature
  • Sugar levels
  • Mineral content
• Hormones


  Chemical messengers carried in the bloodstream that are released by glands and pass to their target organ
• Hormones


  • They take longer to have an effect than nerves but their responses usually last longer
  • Many homeostasis mechanisms involve hormones
• Negative feedback


  A control mechanism where if levels change too much, a hormone is released to bring the change back to the normal level
• Control of blood sugar

  1. Insulin injected by pancreas

  2. Glucose absorbed by tissues

  3. Glucose absorbed by liver

  4. Blood glucose reduced
• What happens when blood glucose is too low


  1. Insulin not injected by pancreas

  2. Less glucose absorbed by tissues

  3. Less glucose absorbed by liver

  4. Blood glucose increased
• Diabetes


  A condition where people do not make insulin so it needs to be injected
• Control of body temperature - when too hot


  1. Sweating

  2. Vasodilation
• If blood temperature gets too high it could lead to heat stroke and dehydration
• Control of body temperature - when too cold


  1. Shivering

  2. Vasoconstriction

  3. Less sweating
• Hypothermia occurs when the blood temperature gets too low and can be fatal
• Controlling body water - when too much


  1. Hypothalamus detects too much water

  2. Pituitary gland releases less ADH

  3. Kidneys absorb more water

  4. More water reaches bladder and is lost through urine

  5. Blood water level returns to normal
• Controlling body water - when too little


  1. Hypothalamus detects too little water

  2. Pituitary gland releases more ADH

  3. Kidneys absorb less water

  4. Less water reaches bladder and is lost through urine

  5. Blood water level returns to normal