B3.3

• Homeostasis

  The regulation of conditions inside the body to maintain a stable internal environment in response to changes in both internal and external conditions
• Cells in the body need certain conditions to function properly, such as not being too hot or too cold, not being too acidic or too alkaline, and having a good supply of glucose and water
• The body regulates everything and makes sure that everything is kept around the right levels
• Temperature and glucose levels do fluctuate, but only within small bounds
• If changes take place outside the body

  The body can still maintain its internal environment
• Automatic control systems


  • Receptors that detect a change
  • Coordination centres that interpret the change and decide what to do
  • Effectors that carry out the change
• Nervous system


  Sends fast and precise electrical impulses through nerves, allowing for quick responses
• Endocrine system


  Relies on hormones released into the bloodstream, which are slower, longer-lasting, and more generalized than the nervous system
• Negative feedback mechanism


  1. If the level of something gets too high, negative feedback decreases it to return it to normal

  2. If the level gets too low, negative feedback increases it to return it to normal
• Homeostasis is the overall process of maintaining a stable internal environment through a loop of negative feedback
• Thermoregulation


  The control of our internal body temperature
• Why we need to regulate temperature

  • Allows our cells to function properly
  • 37 degrees Celsius is the perfect temperature for our enzymes to function
• Thermoregulatory sensor


  Part of the hypothalamus within our brain that acts as a thermostat for our body
• Receptors that detect changes in body temperature


  • Found mostly in the skin and blood vessels
  • Constantly send information about temperature to the thermoregulatory sensor
• Warming up mechanisms


  1. Vasoconstriction (constrict blood vessels near surface of skin)

  2. Contract erector muscles (make hairs stand on end)

  3. Shiver (muscles contract automatically)
• Vasoconstriction


  Less blood flows near the surface, less heat energy is lost to surroundings
• Erector muscles


  Trap a small layer of insulating air, harder to lose heat from skin
• Shivering


  Muscle contraction requires energy from respiration, releases heat as waste
• Cooling down mechanisms


  1. Vasodilation (blood vessels expand)

  2. Produce sweat (evaporation takes heat energy from body)
• Vasodilation


  More warm blood passes close to skin surface, more heat energy transferred to surroundings
• Sweating


  Evaporation of sweat takes heat energy from body
• Blood glucose concentration


  The amount of sugar in our bloodstream
• We need a decent amount of sugar in our blood so that our cells have a constant supply of glucose for respiration
• If the blood glucose concentration gets too high it can start to damage our tissues
• What happens when we eat a big meal with lots of carbohydrates

  1. Carbohydrates broken down in intestines into glucose

  2. Glucose absorbed into bloodstream

  3. Blood glucose concentration increases
• Pancreas


  • Organ that sits just behind the stomach
  • Releases insulin and glucagon hormones
• How insulin regulates high blood glucose

  1. Pancreas detects high glucose

  2. Releases insulin into bloodstream

  3. Insulin binds to cells (liver, muscle)

  4. Cells take up glucose from blood

  5. Blood glucose concentration decreases
• Glycogen


  Long-term storage form of glucose
• How glucagon regulates low blood glucose

  1. Pancreas detects low glucose

  2. Releases glucagon into bloodstream

  3. Glucagon binds to liver cells

  4. Liver breaks down glycogen into glucose

  5. Glucose released into blood

  6. Blood glucose concentration increases
• Insulin and glucagon


  Create a negative feedback loop to keep blood glucose at the right level
• Our bodies constantly release insulin and glucagon to ensure blood glucose is kept at the right level
• What is glucagon?


  A hormone produced by alpha cells of the pancreas that raises blood glucose levels
• Excretion:  the process where waste products are eliminated
• Egestion: eliminating useless material from your system
• Urine:

  1. water
  2. salt
  3. urea
• Blood glucose concentration


  The amount of sugar in our bloodstream
• We need a decent amount of sugar in our blood so that our cells have a constant supply of glucose for respiration
• If the blood glucose concentration gets too high it can start to damage our tissues
• What happens when we eat a big meal with lots of carbohydrates

  1. Carbohydrates broken down in intestines into glucose

  2. Glucose absorbed into bloodstream

  3. Blood glucose concentration increases
• Pancreas


  • Organ that sits just behind the stomach
  • Releases insulin and glucagon hormones