Nerves & Hormones


Senses & Stimuli

We need senses:

  • Find food
  • Avoid predators
  • Find a mate

     Sense           Stimulus ( trigger )           Sense Organ

  • Sight             Light                              Eyes
  • Hearing         Sound                            Ears
  • Taste            Chemicals                      Tongue
  • Smell            Chemicals                      Nose
  • Touch           Temp / Pain / pressure    Skin
  • Balance        Gravity                           Ears

The fingertip is the most sensitive part of the body because the nerve endings are closer together. They are closer together because we mostly touch with our fingertips

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Reflex Actions

Reflex Actions

  • Automatic responses carried out by your body whithout you having to think about it
  • Help you aviod danger and harm because they happen so fast
  • Dont have to go to the brain to make a concious decision, so are faster than voluntary actions
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Synapses are the junction between 2 neurons, which an electrical impulse has to pass

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Hormones // Controlling conditions


  • A substance produced by the body to stimulate specific cells or organs
  • Produced in glands
  • Carried in the bloodstream
  • Eg. Adrenaline, makes the heart beat faster


     Condition to control    Why?                                          How it is kept constant

  • Water                        Can damage cells                           Concentration lost in sweat & urine 
  • Ions                           Affects amount of salt in body         is controlled
  • Body Temperature      Enzymes work best at 37.5  C         Sweating (cool down) & shivering (                                                                                       warm up
  • Blood sugar               Changes after eating, causes chaos Hormones made in pancreas
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Hormones in the Menstrual Cycle


  • Made in the pituitary gland
  • Causes eggs to mature, Stimulates ovary to produce oestrogen


  • Made in the ovary
  • Inhibits FSH production- so only one egg matures
  • Develops lining of womb, Stimulates release of egg


  • Made in the pituitary gland
  • Stimulates release of the egg


  • Made in the ovary
  • Inhibits FSH and LH production
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Hormones in Contraception & IVF

Combined Pill:

  • Contains oestrogen & progesterone
  • Oestrogen inhibits FSH production
  • Progesterone inhibits FSH and LF production

Progesterone- Only Pill ( Mini Pill ):

  • Contains only progesterone
  • Progesterone inhibits FSH and LF production

The Pill was first used in the UK in 1961


  • Some women are infertile because they don't have enough of a hormone
  • IVF means that the sperm and egg are fertilised outside of the womb, then placed into the womb
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Hormones in Fertility Treatment (IVF)

The process:

Fertility drugs are used to mature lots of eggs ( FSH )

The eggs are collected from the womb and placed in a solution in a Petri dish

A sample of semen is mixed with the eggs

The eggs are checked regularly to make sure that they develop properly

When the fertilised eggs are balls of cells, they are placed back into the mothers womb

This is not always sucessful

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