B11 - Hormonal coordination

• The endochrine system


  • Compossed of glands that secrete chemicals called hormones into the bloodstream
  • The blood carries the hormones to a target organ, where an effect is produced
• Compared to the nervous system, the effects caused by the endochrine system are slower but act for longer
• The pituatary gland

  • Located in the brain
  • Secretes several hormones into the blood
• Blood glucose levels 


  • Monitored and controlled by the pancreas
  • A negative feedback loop
  • The pancreas switches production between insulin and glucagon to control blood glucose levels
• Blood glucose negative feedback loop


  • Blood glucose too high
  • detected by the pancreas
  • insulin released
  • glucose moves from the blood into cells
  • excess glucose converted to glycogen in the liver and muscle cells for storage
  • blood glucose falls to normal levels
  • Blood glucose too low
  • detected by the pancreas
  • glucagon released
  • glycogen converted into glucose and released into the blood
  • amino acids/fats broken down
  • blood glucose rises to normal levels
• Diabetes


  • A non-communicable disease
  • The body cannot respond to or produce insulin
  • Leads to uncontrolled blood glucose levels
• Type 1 diabetes


  • early onset
  • pancreas stops producing sufficient insulin
  • commonly treated through insulin injections, also diet control and exercise
• Type 2 diabetes


  • usually later onset
  • obesity is a risk factor
  • body doesn't respond to insulin produced
  • commonly treated through a carbohydrate-controlled diet and exercise
• Negative feedback


  • work to maintain a steady state
  • blood glucose, water, and thyroxine levels are all controlled in the body by negative feedback
• Adrenaline 


  • produced by adrenal glands in times of fear or stress
  • increases heart rate
  • boots delivery of oxygen and glucose to muscles
  • prepares the body for the fight or flight response
  • does not involve negative feedback - adrenal glands stop producing adrenaline
• Thyroxine


  • produced by the thyroid gland
  • regulates how quickly your body uses energy and makes proteins (metabolic rate)
  • important for growth and development
  • levels controlled by negative feedback
• Oestrogen


  • main female reproductive hormone
  • causes female secondary sex characteristics to develop
  • produced in the ovary
  • at puberty, eggs begin to mature and one is released around every 28 days
• Testosterone


  • main male reproductive hormone
  • causes male secondary sex characteristics to develop
  • produced in the testes
  • stimulates sperm production
• Hormones in the menstrual cycle

  • Folicule Stimulating Hormone (FSH)
  • Lutenising Hormone (LH)
  • Oestrogen
  • Progesterone
• FSH in the menstrual cycle

  • Folicle Stimulating Hormone
  • released by the pituatary gland
  • causes eggs to mature in the ovaries
  • stimulates ovaries to produce oestrogen
• LH in the menstrual cycle


  • released by the pituatary gland
  • stimulates the release of mature eggs from the ovaries (ovulation)
• Oestrogen in the menstrual cycle


  • released by the ovaries
  • causes lining of uterus wall to thicken
  • inhibits release of FSH
  • stimulates release of LH
• Progesterone in the menstrual cycle


  • released by the ovaries
  • maintains thick uterus lining
  • inhibits release of FSH and LH
• Hormonal contraception


  • Oral contraceptives
  • contain hormones to inhibit FSH production so no eggs mature
  • Implant
  • slows release of progesterone to inhibit maturation and release of eggs, which can last months or years
• Non-hormonal contraception


  • Barrier contraception
  • e.g. condoms
  • prevent sperm reaching the egg
  • Intrauterine devices
  • prevent the implantation of an embryo
  • can also release hormones, like oral contraceptives
  • Spermicidal agents
  • kill or disable sperm
  • Abstinence
  • can be permanent celibacy or just when an egg may be in the oviduct
  • Surgical methods of male and female sterilisation
• IVF (in vitro fertilisation)


  • mother given FSH and LH to stimulate the maturation of several eggs
  • eggs collected from the mother and fertilised by sperm from the father in a lab
  • fertlised eggs begin to develop into embryos
  • one or two embryos are inserted into the mother's uterus when the embryos are still only a few cells
• Phototropism


  The orientation and growth of plants in response to light
• Gravitropism


  The growth of plants in response to gravity
• Plant hormones


  • auxins
  • ethene
  • gibberellins
• Auxins


  • plant growth regulator
  • unequal distributions cause unequal growth rates in plant roots and shoots
  • uses:
  • weedkiller
  • rooting powder
  • promoting growth in tissue cultures
• Ethene


  • acts as a hormone to control cell division
  • uses:
  • controls ripening of fruit during storage and transport
• Gibberellins


  • regulates developmental processes
  • includes initiating seed germination
  • uses:
  • end seed dormancy
  • promote flowering
  • increase fruit size