Edexcel IGCSE Biology 复习笔记 2.10.13 The Role of Hormones: Advanced

• As well as adrenaline, insulin, testosterone, progesterone and oestrogen, the following hormones are also of great importance in humans:
  • ADH (antidiuretic hormone)
  • FSH (follicle-stimulating hormone)
  • LH (luteinising hormone)

   

ADH and its role in osmoregulation

• If the water content of the blood falls below a certain level:
  • The blood is too concentrated
  • Receptors detect this and stimulate the pituitary gland to release more ADH
  • This causes the collecting ducts of the nephrons to become more permeable to water
  • This leads to more water being reabsorbed from the collecting ducts
  • The kidneys produce a smaller volume of urine that is more concentrated (contains less water)

   

• If the water content of the blood rises above a certain level:
  • The blood is too dilute
  • Receptors detect this and stimulate the pituitary gland to release less ADH
  • This causes the collecting ducts of the nephrons to become less permeable to water
  • This leads to less water being reabsorbed from the collecting ducts
  • The kidneys produce a larger volume of urine that is less concentrated (contains more water)

   

Hormonal control of the menstrual cycle

• Four hormones control the events that occur during the menstrual cycle. These are:
  • Oestrogen
  • Progesterone
  • FSH (follicle-stimulating hormone)
  • LH (luteinising hormone)

   

• Oestrogen and progesterone are involved in maintaining the uterus lining
  • Oestrogen is produced by the ovaries and progesterone is produced by an empty egg follicle called the corpus luteum

   

• The other two hormones are produced by the pituitary gland in the brain:
  • FSH causes the maturation of an egg in the ovary
  • LH stimulates the release of the egg

   

The roles of FSH and LH

• FSH is released by the pituitary gland and causes an egg to start maturing in the ovary
• It also stimulates the ovaries to start releasing oestrogen
• The pituitary gland is stimulated to release LH when oestrogen levels have reached their peak
• LH causes ovulation to occur and also stimulates the ovary to produce progesterone

Changes in the levels of the pituitary hormones FSH and LH in the blood during the menstrual cycle

Other Important Hormones in the Human Body Table