GCSE AQA Biology 1 Nerves & Hormones

1. Contain receptors - groups of cells which are sensitive to stimulus (change stimulus energy into electrical impulses)
2. Eyes - light receptors
3. Ears - sound & balance receptors
4. Nose - smell receptors
5. Tongue - taste receptors
6. Skin - sensitive to touch, pressure, pain & temp. change

1. Where info from sense organs is sent & reflexes/actions are coordinated
2. Consists of brain & spinal cord
3. Neurones transit info quickly to & from CNS
   1. Sensory neurones - carry signals from receptors to CNS
   2. Relay neurones - carry signals from sensory to motor neurones
   3. Motor neurones - carry signals from CNS to effector
4. Instructions from CNS sent to effectors
   1. Muscles & glands - contract or secrete hormones

1. Chemical set off new electrical signal in next neurone

1. Neurones go through spinal cord or unconscious part of brain
2. 1) STIMULUS - detected by receptors
   1. 2) SENSORY NEURONE - impulses sent along to CNS
      1. 3) RELAY NEURONE - impulses reach synapse between sensory & relay, chemicals cause impulses to be sent along relay neurone
         1. 4) MOTOR NEURONE - impulses reach synapse between relay and motor, chemicals cause impulses to be sent along motor neurone
            1. 5) EFFECTOR - impulses travel to effector
               1. 6) RESPONSE - muscle contracts/gland secretes

1. Very fast action
2. Act for very short time
3. Act on very precise area

1. Slower action
2. Act for long time
3. Act in more general way

1. 1) Bleeding starts - uterus lining breaks down
   1. 2) Uterus lining builds up
      1. 3) Egg is released
         1. 4) Wall is maintained

1. FSH
   1. Produced by pituitary gland
      1. Causes egg to mature
         1. Stimulates release of oestrogen
2. Oestrogen
   1. Produced in ovaries
      1. Causes pituitary gland to produce LH
         1. Inhibits release of FSH
3. LH
   1. Produced by pituitary gland
      1. Stimulates release of egg

1. Oestrogen can prevent release of egg - inhibits FSH
2. Progesterone also reduces

   Nota:

   • Produces thick cervical mucus, stops any sperm getting through
3. The Pill

   Nota:

   • Used to be version with high levels but there was link with blood clots - now contains lower doses of oestrogen
   1. Pros

      Nota:

      • * Over 99% effective at preventing pregnancy * Reduces risk of getting some types of cancer
   2. Cons

      Nota:

      • * Isn't 100% effective * Can cause side effects * Doesn't protect against STDs

1. Some women have low levels of FSH - don't cause eggs to mature
   1. Can inject FSH & LH to stimulate egg release
2. Pros

   Nota:

   • * Helps women to get pregnant
3. Cons

   Nota:

   • * Doesn't always work - may have to do it many times (expensive) * Too many eggs could be stimulated - multiple pregnancies

1. Involves collecting eggs from woman's ovaries and fertilising with man's sperm - grown into embryos
   1. Once ball of cells - 1 or 2 transferred to uterus
      1. FSH & LH given before egg collection
2. Pros

   Nota:

   • * Can give infertile couple a child
3. Cons

   Nota:

   • * Some women have strong reaction to hormones e.g. abdominal pain, vomiting & dehydration * Reported increased risk of cancer * Multiple births - risky for mother & babies

1. Controls growth near tips of shoots & roots
   1. In response to light, gravity & moisture
2. Produced in tips, moves backwards - enlarging

   Nota:

   • If tip is removed, may stop growing
3. STIMULATES growth in SHOOTS, INHIBITS growth in ROOTS

Nota:

• * More auxin accumulates on shaded side * Grows faster on that side - shoot bends towards light

Nota:

• * When shoot is growing sideways, gravity produces unequal distribution - it will have more auxin on lower side * Lower side grows faster - bending shoot upwards

Nota:

• * Root growing sideways will have more auxin on lower side * Auxin will inhibit growth - top side grows faster, root bends downwards

Nota:

• * Uneven amount of moisture produces more auxin on side with more moisture * Inhibits growth - further side grows faster, root bends towards moisture

1. Weedkillers

   Nota:

   • Most weeds in crop field broad-leaved (unlike crops), weedkillers made of plant hormones only affect broad-leaved plants (disrupt normal growth patterns - kills them)
2. Rooting powder

   Nota:

   • Plant cuttings won't alays grow in soil, add rooting powder containing auxin - produces roots rapidly