Homeostasis

• What is homeostasis?

  The maintenance of a constant internal environment.
• What do hormones do?

  Carry messages around the body in the blood. It’s a chemical message which is slow in comparison to the nervous system.
• What hormone is responsible for glucose regulation?

  Insulin
• Where is insulin produced?

  The pancreas
• What happens if your glucose level is too high?

  Insulin is secreted into blood (beta cells), liver converts glucose into glycogen, glucose levels will then decrease
• What happens if your glucose level is too low?

  Glucagon is secreted into blood (alpha cells), liver converts glycogen into glucose, glucose levels increase
• What is negative feedback?

  If the level of something increases, control systems will work to reduce it again. If the level of something falls, control systems raise it again.
• What are 2 examples of negative feedback?

  Glucose control and after fast exercise
• What temperature is body temperature?

  37 degrees
• What happens to hairs when you are too warm?

  Hair erector muscle relaxes, thin layer of air is trapped, more heat is lost to surroundings
• What happens to hairs when you are too cold?

  Hair erector muscle contracts, thick layer of air is trapped, air insulates skin so less heat is lost
• How does sweating cool the body?

  Evaporates off the body, taking heat energy with it
• What is vasodilation?

  Blood vessels dilate, blood flows at surface of skin, removes heat by radiation
• What is vasoconstriction?


  Blood vessels constrict, less blood flows at surface of skin, less heat is lost by radiation.
• Why does shivering increase temperature?

  Fast muscle contractions, respiration releases heat energy
• What are tropisms?

  A growth response of a plant to a one sided stimulus
• What is a phototropism?


  A plant growth response where the stimulus is light
• What is a positive gravitropism?

  A growth response where the stimulus is gravity
• What is auxin?

  A plant hormone produced mostly in the tips of growing stems and roots, which can diffuse to other parts of the stem or roots.
• What happens if there is a high conecentration of auxin?

  Cells in stems grow more, cells in roots grow less
• How does auxin affect a positive phototropism?


  The shaded side of the stem contains more auxin which makes it grow longer so that the stem bends towards the light
• What can disrupt homeostatic mechanisms?

  Diabetes, alcohol and obesity
• What is diabetes?


  A medical condition where blood glucose levels remain too high.
• How is type 1 diabetes caused?

  Damage to beta cells in pancreas which produce insulin. Usually diagnosed in children.
• What happens in type 1 diabetes?

  The body doesn’t produce/ too little insulin.
• How is type 1 diabetes managed?

  Regular injections of insulin
• What happens in type 2 diabetes?

  Where the body becomes resistant to insulin
• How is type 2 diabetes managed?

  Regular intense exercise and low carbohydrate/ sugar diet
• What lifestyle factors can induce type 2 diabetes?

  Drinking excessive amounts of alcohol, drug misuse, obesity, high blood pressure
• What does Benedict's solution test for?

  Glucose
• What colour does Benedict's solution turn?

  Blue to brick red
• What does Biuret solution test for?

  Protein
• What colour does Biuret solution turn?

  Blue to purple
• What colour does iodine test turn?

  Brown to blue/black
• How is percentage change calculated?

  Difference

  --------- x 100

  Original
• What is a hydrotropism?

  Where a plant grows in the direction of water