Coordination and control

• Nervous system 


  Anything around us that we respond to is called a stimulus.

  In animals stimuli (sound, sight, smell) affect receptors. There are many types of receptors each responding to a type of stimulus.

  If a receptor is stimulated it may cause an effector such as a muscle or gland to produce a response
• Nerve cells 


  Nerve cells or neurones link the receptors to a coordinator. This is the central nervous system, consisting of brain and spinal cord. The role is to make sure the correct receptor is linked to the correct effector.

  A neurone carries info in the form of small electrical charges called nerve impulses
• Voluntary and reflex actions 


  These are the two main types of nervous action

  Voluntary - slow, involve thinking time and brain, conscious control

  Reflex - fast, no thinking time
• Reflex arc 


  The pathway of neurones in a reflex action

  
• Plant hormones 


  Phototropism is the growth response involving plants bending in the direction of light. When a plant experiences uneven light, more of the hormone auxin passes to the shaded side. The auxin causes increased elongation of cells on the shaded side, resulting in uneven growth and the plant bending towards the light