Reflexes and reflex arcs

• What are reflexes?

  Fast automatic responses to certain stimuli
• Reflexes

  Fast automatic responses to certain stimuli

  Bypass your conscious brain completely when a quick response is essential

  Can reduce your chance of being injured
• Examples of reflexes

  If someone shines a bright light in your eyes your pupils automatically become smaller

  Adrenaline is a hormone which gets your body for action. If you get a shock your body releases adrenaline automatically
• What is a reflex arc?

  The passage of information in a reflex , from receptor to effector
• Reflex arc

  Passage of information in a reflex, from receptor to effector

  Neurones in reflex arcs go through the spinal chord or through an unconscious part of the brain
• The main stages in a reflex arc

  1. When a stimulus is detected by receptors, impulses are sent along a sensory neurone to a relay neurone in the CNS
  2. When the impulses reach a synapse between the sensory neuron and the relay neurone, they trigger chemicals to be released. These chemicals cause impulses to be sent along the relay neurone
• 3. When the impulses reach a synapse between the relay neurones and a motor neurone, the same thig happens. Chemicals are released and cause impulses to be sent along the motor neurone

  4. The impulse then travel along the motor neurone to the effector, which is usually a muscle
• 5. If the effector is a muscle, it will respond to the impulse by contracting. If its a gland, it will secrete a hormone