reflex actions 5.2.1

• a reflex action is a rapid automatic response of the nervous system that does not involve conscious thought
• examples of reflex actions include:

  • pupils dilating in response to light changes
  • danger (heat)
  • breathing reflex
  • CO2 detection
  • coughing
• conscious actions involve relay neurones
• reflex actions only use the spinal chord
• reflex actions do not need to be learned
• reflexes are important because they keep you safe from injury and created enhanced children when reproducing
• reflexes are faster than conscious actions because it has less distance to travel because it does not have to pass through the brain first, also because there is only one relay in a reflex, whereas conscious decisions will have many relay neurones, therefore reflex actions involve fewer synapses
• reflex arc:

  1. stimulus occurs
  2. stimulation of receptor
  3. impulse travels along a sensory neurone
  4. impulses are passed along a relay neurone via a synapse
  5. impulses travel along a motor neurone via a synapse
  6. when impulses reach muscle, it contracts