Regulation

• Regulation


  The amount of glucose in the blood is controlled by hormones (chemical messengers) that travel in blood from the gland where they are produced
• Glucose is needed by cells for respiration
• The concentration of glucose in the blood should be maintained at a constant level
• Insulin


  A hormone produced by the pancreas that regulates glucose levels in the blood
• Low glucose


  1. Insulin not secreted

  2. Does not convert glucose into insoluble glycogen

  3. Blood glucose increases
• High glucose


  1. Insulin secreted into blood

  2. Converts glucose into insoluble glycogen

  3. Blood glucose decreases
• Glycogen is stored in the liver
• Insulin and glucagon are released from the pancreas
• High levels of glucose

  1. Too much glucose in blood

  2. Pancreas produces insulin which enters blood

  3. Liver converts excess into insoluble glycogen and stores it

  4. Blood glucose reduced
• Low levels of glucose


  1. Normal levels of glucose in blood

  2. Insulin not produced by the pancreas

  3. Liver does not convert glucose into insoluble glycogen

  4. Blood glucose remains the same
• Diabetes


  A condition in which the blood glucose levels remain too high
• Diabetes


  • Can be treated by injecting insulin
  • The extra insulin causes the liver to convert glucose into glycogen which reduces the blood glucose level
• Type 1 diabetes

  • Caused by damage to the beta cells in the pancreas which produce insulin
  • People with type 1 produce little or no insulin
• Controlling type 1 diabetes

  • Following a low sugar/carb diet
  • Injecting insulin
  • Possible transplant of pancreatic tissue
• People with type 1 diabetes have to monitor their blood sugar levels throughout the day, as their levels of physical activity and diet affect the amount of insulin needed
• Type 2 diabetes

  • Caused by a person's body becoming resistant to insulin
  • Can be controlled by diet and exercise
• Rising levels of obesity

  Increasing levels of type 2 diabetes
• Alcohol


  • Even in small amounts, it increases the body's reaction time
  • Addictive, people can become dependent on it and suffer withdrawal symptoms without it
  • Can cause long-term physical damage to major organs such as the liver and circulatory system
• Regulating temperature


  Important to maintain body temperature at 37°C as this is the temperature at which the body's enzymes work best
• Hairs on the skin


  • Help to control body temperature
  • Lie flat when warm, rise when cold
• When too warm

  1. Hair erector muscle relaxes, lowering the hair

  2. Thin insulating layer of air is trapped above the skin

  3. More heat is lost to the environment
• When too cold

  1. Hair erector muscle contracts, raising the hair

  2. Thicker layer of air above the skin insulates against heat loss
• Vasodilation


  A response to being too warm, where blood vessels in the skin widen so more heat from the blood is lost to the environment
• Vasoconstriction


  A response to being too cold, where blood vessels narrow so less heat is lost from the blood to the environment
• Sweating


  A mechanism used by the body to cool down, where a layer of liquid sweat is released onto the skin and evaporates, moving heat away
• Sweating is caused by involuntary contractions of the muscles, which require energy from respiration and release heat
• Tropism


  Plant growth response to light, gravity or water (stimuli), caused by the release of the hormone auxin
• Positive tropism


  When a plant grows towards the stimulus
• Negative tropism

  When a plant grows away from the stimulus
• Stem response to light


  • Positive phototropism (grows towards the light)
• Root growth response to gravity


  • Positive geotropism (grows towards the direction of the force of gravity)
• High concentrations of auxin


  Cells in stems grow more, cells in roots grow less
• Phototropism in a stem

  The shaded side contains more auxin and grows longer, causing the stem to bend towards the light
• Geotropism in a root placed horizontally


  The bottom side contains more auxin and grows less, causing the root to bend in the direction of the force of gravity
• Geotropism in a stem placed horizontally


  The bottom side contains more auxin and grows more, causing the stem to bend upwards against the direction of the force of gravity