Hormones

• FSH is secreted by the pituitary gland and causes eggs to mature in the ovaries in the first part of the cycle. Then it stimulate the ovaries to produce oestrogen.
• Oestrogen is secreted by the ovaries. It inhibits FSH release. Stimulates LH release. Makes the lining of the uterus grow again after menstruation.
• LH is secreted by the pituitary gland and stimulates the release of an egg from the ovary in ovulation.
• Progesterone is secreted by empty follicle in the ovaries and maintains the lining of the uterus durning the second half of the cycle. It inhibits both FSH and LH release.
• The endocrine system is made up of glands that secrete hormones directly into the bloodstream
• Hormones are chemical messengers carried in the blood to a target organ where they produce an effect
• Compared with effects of the nervous system, the effects of hormones are slower and act for longer
• The pituitary gland in the brain is a 'master gland' that secretes several hormones in response to body conditions
• Some pituitary hormones act on other glands to stimulate the release of other hormones and bring about effects
• Adrenaline:

  • Produced by the adrenal glands in times of fear or stress
  • Increases the heart rate, boosting the delivery of oxygen and glucose to the brain and muscles
  • Prepares the body for 'flight or fight'
• Thyroxine:

  • Produced by the thyroid gland
  • Increases the metabolic rate
  • Controls growth and development in young animals
  • Controlled by negative feedback
• Blood glucose concentration is monitored and controlled by the pancreas
• If blood glucose concentration is too high:

  • Pancreas releases more insulin
  • Insulin causes glucose to move from blood into cells
  • Excess glucose in liver and muscle cells is converted to glycogen for storage
• If blood glucose concentration is too low:

  • Pancreas releases glucagon
  • Glucagon stimulates glycogen to be converted into glucose and released into the blood
• Type 1 diabetes:

  • Caused by pancreas failing to produce sufficient insulin
  • Results in uncontrolled high blood glucose levels
  • Normally treated with insulin injections