Biology P2

• Pituitary Gland

  • produces hormones that Regulates body temp
• Thyroid gland

  • Produces thyroxin
  • regulated rate of metabolism, heart rate and temp - when blood thyroxine level is low, the hypothalamus is stimulated to release TRH (thyrotropin releasing hormone) which stimulates Pituitary gland to release TSH (thyroid stimulating hormone) This stimulates thyroid gland to release thyroxine which reduces levels of TRH and cycle repeats
• Ovaries

  • Produces Oestrogen
• Adrenal Glands

  • produces adrenaline which increases supply of oxygen and glucose to cells by binding to receptors in heart causing it to pump more blood and to receptors in liver to make it break down glycogen into glucose
• the pancreas

  • produces insulin which regulates blood glucose level
• FSH

  • released by pituitary gland
  • causes a follicle (egg) to mature in one of the ovaries
  • stimulates oestrogen production in ovaries
• Oestrogen

  • released by ovaries
  • causes lining of uterus to grow and thicken
  • high level stimulates a LH surge
• LH

  • released by pituitary gland
  • stimulates ovulation at day14 - the follicle ruptures and releases egg
  • stimulates the remains of the follicle to develop into the corpus luteum which secretes progesterone
• Progesterone

  • Maintains lining of uterus
  • inhibits FSH and LH
  • when this falls uterus lining breaks down
  • low level of this allows FSH to increase and repeat cycle
  • if pregnant this stays high
• Clomifene therapy - treat infertility 


  a drug that cause FSH and LH to be released in the body which stimulate egg production and ovulation
• Homeostasis 


  maintaining the right conditions in the body so the body works properly

  Include :

  • osmoregulation
  • thermoregulation
  • blood glucose regulation
• Blood glucose regulation

  • Eating foods containing carbs puts glucose in the blood.
  • normal metabolism of cells removes glucose from the blood (respiration)
  • excess glucose is stored in the liver and muscles as glycogen
  • when stored are full then the excess glucose is stored as lipid(fat)
  • changes in blood glucose is controlled by the pancreas where it secretes insulin and glucagon to go to liver to turn glycogen into glucose (glucagon) or glucose into glycogen (insulin)
• thermoregulation

  • keeping internal temp steady
  • controlled by the hypothalamus where the thermoregulatory centre in it contains receptors that are sensitive to blood temp in brain.
  • It also receives impulses from receptors in skin that provide info about external temp
  • when too hot hairs lie flat, sweat production increases, blood vessels close to skin widen so allow more energy transferred to surroundings
  • when too cold the opposite happens + shiver which increases respiration which is exothermic
• osmoregulation in the kidneys

  • regulating water content
  • if conc of water in blood to high then water moves into body cells by osmosis - too much can cause cells to burst - cells shrink when water leaves cells
• The kidneys

  1. remove urea from the body which is produced in liver from breakdown of excess amino acids
  2. adjusts ion levels in blood
  3. adjust water content in blood

  They fo this by filtering stuff out the blood under high pressure and then transporting useful things. end product is urine
• The nephron in the Kidney are the filtration units

  1. liquid part of blood is forced out of glomerulus and into bowmans capsule at high pressure. bigger mole uses and bloods cells can’t pass through membrane so aren’t forced out
  2. as liquid flows along nephron, useful substances are reabsorbed: water is absorbed according to level of hormone ADH
  3. whatevwe isn’t absorbed continues out the nephron via collecting duct and passes into the ureter and into bladder as urine
• ADH makes water reabsprbed in kidneys nephrons 


  Does this by making the nephron more permeable so water is reabsorbed
• Dialysis filter

  1. for patients with kidney failure
  2. has to be done regularly to keep dissolved supstances at right conc and filter out waste
  3. dialysis fluid has same conc of salts and glucose as blood plasma
  4. barrier is permeable to things like ions and waste but not big molecules
• cardiac output = heart rate x stroke volume
• nitrogen fixing bacteria


  turn atmospheric N2 into ammonia
• denitrifying bacteria 


  turns nitrate into n2
• nitrifying bacteria 


  turn ammonia into nitrates
• decomposers


  decomposes proteins into ammonia