B3

• Nervous system


  What lets you act to what goes on around you
• Central Nervous System


  • Coordinates a response
• Nervous system response


  1. Sensory receptors detect stimulus

  2. Information sent as electrical impulses along sensory neurons to CNS

  3. CNS coordinates response

  4. CNS sends information to effector along motor neuron

  5. Effector responds
• Neurones


  Nerve cells that transmit information as electrical impulses
• Sensory and motor neurones

  • Have branched endings (dendrites) to connect with other neurones
  • Some axons surrounded by myelin sheath to speed up impulses
  • Neurones are long to speed up impulses
• Synapse


  Connection between neurones, where transmitter chemicals are released
• Reflex actions


  • Automatic responses, quicker than normal
  • Sensory neurone connects directly to motor neurone, bypassing conscious brain
  • Often have a protective role
• Hormones


  Chemical messengers sent in the blood
• Endocrine system


  • Glands that produce and release hormones
• Target cells


  Cells that have the right receptors to respond to a particular hormone
• Adrenaline


  Hormone that prepares the body for 'fight or flight'
• Adrenaline response


  1. Increases heart rate and blood pressure

  2. Increases blood flow to muscles

  3. Increases blood glucose level
• Negative feedback


  • Body can control hormone levels by triggering a response to bring them back to normal
• Thyroxine


  Hormone that regulates metabolic rate
• Thyroxine regulation


  1. Thyroxine released by thyroid gland

  2. In response to thyroid stimulating hormone (TSH) from pituitary gland

  3. Negative feedback inhibits TSH when thyroxine level is high
• Testosterone


  Main male sex hormone
• Oestrogen


  Main female sex hormone
• Progesterone


  Hormone involved in menstrual cycle and pregnancy
• FSH and LH


  Hormones from pituitary gland that help control menstrual cycle
• Menstrual cycle


  1. Menstruation

  2. Uterus lining builds up

  3. Egg released (ovulation)

  4. Uterus lining maintained
• Menstrual cycle hormones


  • FSH stimulates egg maturation and oestrogen production
  • Oestrogen stimulates LH release and uterus lining growth
  • LH triggers ovulation and progesterone production
  • Progesterone maintains uterus lining
• Infertility


  Inability to reproduce naturally
• Treating infertility with hormones

  1. Injecting FSH and LH to stimulate ovulation

  2. IVF - collecting eggs, fertilising in lab, implanting embryos
• Hormones


  Play a big role in reproduction
• Hormones are used to help infertile women get pregnant and to help fertile women have babies
• Infertility


  Means a person can't reproduce naturally
• Treating infertility with modern reproductive technologies

  Involves hormones
• Hormones used to promote natural pregnancy

  1. Stimulate ovulation by injecting FSH and LH

  2. Ovulation doesn't occur due to low FSH levels
• IVF (in vitro fertilization)


  1. Collect eggs from woman's ovaries

  2. Fertilise with man's sperm in lab

  3. Grow into embryos

  4. Transfer embryos to woman's uterus
• Hormones used in IVF

  FSH and LH given before egg collection to stimulate egg production
• Contraceptive methods involving hormones

  • Injection
  • Implant
  • Intrauterine system (IUS)
  • Mini-pill
  • Combined pill
  • Patch
• Hormones in contraceptives


  Progesterone - Stimulates thick cervical mucus, thins uterine lining

  Oestrogen - Also prevents ovulation by inhibiting FSH
• Hormonal contraceptive methods are more than 99% effective if used correctly
• Non-hormonal contraceptive methods


  • Barrier methods (condom, female condom, diaphragm)
  • Intrauterine devices (IUDs)
  • Natural methods (fertility awareness, withdrawal)
  • Sterilisation
• Pros and cons of contraceptive methods

  • Side-effects of hormonal methods

  Possibility of 'doing it wrong' with barrier/natural methods

  Medical input required for some methods

  Length of action - long-lasting vs daily/each time

  Protection against sexually transmitted infections
• Insulin


  Hormone that lowers blood sugar level by moving glucose from blood into cells
• Glucagon


  Hormone that raises blood sugar level by releasing glucose from the liver
• Maintaining constant blood sugar level

  Pancreas monitors and controls using insulin and glucagon
• Diabetes


  Condition affecting ability to control blood sugar level
• Type 1 diabetes


  • Pancreas produces little or no insulin

  Requires insulin therapy to remove glucose from blood