Biology Paper 2

• Homeostasis


  Maintaining a Constant Internal Environment
• Homeostasis


  1. Control of Blood Glucose

  2. Regulating body temperature

  3. Maintaining other conditions in the body
• Homeostasis is important for keeping processes in your body ticking over nicely
• Blood glucose concentration


  The amount of glucose in the blood
• Insulin and Glucagon Control Blood Glucose Concentration

  1. Glucose from food enters the blood

  2. Normal metabolism moves glucose from the blood

  3. Excess glucose stored as glycogen or fat

  4. Changes in blood glucose monitored and controlled by the pancreas
• Blood glucose concentration is too high


  Insulin is added to reduce it
• Blood glucose concentration is too low

  Glucagon is added to increase it
• Type 1 Diabetes


  • Lack of insulin production
  • Insulin needs to be injected
• Type 2 Diabetes


  • Person becomes resistant to insulin
  • There is a lack of insulin as well as resistance to it
  • Often linked to obesity and lack of exercise
• Learn about the definition of homeostasis and how blood glucose concentration is regulated by insulin and glucagon
• Explain how blood glucose concentration is returned to normal when it has become too high
• Endocrine glands include the pituitary gland, thyroid gland, parathyroid glands, adrenal glands (including the adrenal medulla), pancreas, ovaries/testes, and pineal gland.
• Menstrual Cycle


  Monthly sequence of events in which the female body releases an egg and prepares the uterus for possible fertilisation
• Stages of the Menstrual Cycle

  • Stage 1: Menstruation starts
  • Stage 2: Uterine lining breaks down and is released
  • Stage 3: Uterine lining is repaired and becomes thick and spongy
  • Stage 4: Egg is released from ovary (ovulation) and uterine lining is maintained
• Menstrual Cycle


  • Controlled by 4 hormones: FSH, LH, Oestrogen, Progesterone
• Role of FSH


  1. Released by pituitary gland

  2. Causes follicle (egg and surrounding cells) to mature in ovary

  3. Stimulates oestrogen production
• Role of Oestrogen


  1. Released by ovaries

  2. Causes uterine lining to thicken and grow

  3. High levels stimulate LH surge
• Role of LH


  1. Released by pituitary gland

  2. LH surge stimulates ovulation

  3. Stimulates corpus luteum to develop and secrete progesterone
• Role of Progesterone


  1. Released by corpus luteum after ovulation

  2. Maintains uterine lining

  3. Inhibits release of FSH and LH
• When progesterone level falls and oestrogen is low, the uterine lining breaks down
• Low progesterone allows FSH to increase, restarting the menstrual cycle
• If a fertilised egg implants, progesterone level stays high to maintain the uterine lining during pregnancy