hormonal control

• hormones


  chemical messengers that are produced in the glands and carried by the blood to specific organs in the body
• the endocrine system is made up of glands that produce and secrete hormones
• hormones regulate the activity of cells or organs
• hormones regulate

  • body's growth
  • metabolism
  • sexual development and function
  • physical and chemical processes in the body
• endocrine system

  • pituitary gland
  • thyroid
  • adrenal glands
  • pancreas
  • ovaries
  • testes
• the pancreas monitors blood glucose levels using insulin and glucagon
• the pancreas is a gland
• blood glucose levels are controlled to provide cells with a constant supply of energy
• when your blood sugar is high your pancreas produces insulin which tells your liver to turn glucose from your blood into glycogen stores
• when your blood sugar is low your pancreas secretes glucagon which breaks down glycogen stores from your liver into glucose
• diabetes 


  the body can't control blood sugar levels
• type 1 diabetes

  • people are born with it and it develops when they are young
  • can be treated by injecting insulin several times a day to keep blood sugar levels normal
• type 2 diabetes

  • is linked to obesity
  • usually diagnosed in older people
  • can be treated through diet and exercise
  • the pancreas still makes insulin but not enough
• puberty happens because of sex hormones produced by the testes and ovaries
• secondary characteristics 


  develop during puberty

  • underarm hair
  • pubic hair
  • body smell
  • emotional changes
  • growth rate increases
• oestrogen is the main female reproductive hormone produced by the ovary
• testosterone is the male reproductive hormone produced by the testes to stimulate sperm production
• male secondary characteristics

  • voice breaks
  • shoulders get wider
  • hair grows on face and chest
• female secondary characteristics

  • breasts develop
  • hips get wider
  • ovaries start to release eggs (menstruation begins)
• FSH is released by the pituitary gland

  stimulates the production of oestrogen and causes an egg to develop

  oestrogen is produced in the ovaries

  causes the lining of the uterus to thicken and grow, inhibits the production of FSH and stimulates the production of LH

  LH is produced in the pituitary gland

  inhibits the production of oestrogen, stimulates the release of an egg and stimulates the production of progesterone

  progesterone is produced in the ovaries

  it maintains the lining of the uterus and inhibits LH production

  when levels fall the uterus lining breaks down
• negative feedback 


  high levels of one hormone inhibit the production of another hormone
• fertility can be controlled by hormonal and non hormonal methods of contraception
• FSH and LH can be used as fertility drugs to stimulate ovulation in women with low FSH levels
• IVF uses FSH and LH to stimulate maturation of ova that are collected
• IVF can be stressful, unsuccessful and often lead to risky multiple births
• IVF

  1. Stimulate ovulation using FSH
  2. egg retrieval from ovaries
  3. fertilisation of eggs
  4. embryo matures
  5. transfer the embryo to uterus
• thyroxine


  stimulates the basic metabolic rate

  growth and development
• adrenaline

  • produced in times of fear or stress
  • increases heart rate to prepare for fight or flight
• plants need light and water for photosynthesis and they have developed responses called tropisms to help make sure they get to these sources
• phototropism


  growth in response to the direction of light
• gravitropism 


  growth in response to the direction of gravity
• auxin 


  a plant hormone responsible for controlling the direction of growth of root tips and stem tips in response to different stimuli including light and gravity
• auxin is made at the tips of the stems and roots
• unequal distribution of auxin leads to unequal growth
• auxin controls the growth of plants by promoting cell division and causing elongation in plant cells
• stems and toots response differently to high concentrations of auxin
• high concentration of auxin

  • cells in stems grow more
  • cells in roots grow less
• gibberellins


  a group of plant hormones responsible for growth and development
• germination


  low concentrations can be used to increase speed of germination
• gibberellins can be used to

  • end seed dormancy
  • promote flowering
  • increase fruit size