Reflexes

• Reflexes

  rapid, automatic responses to certain stimuli that don't involve the conscious part of the brain
• Reflexes can reduce the chances of being injured , e.g. if someone shines a bright light in your eyes, your pupils automatically get smaller so that less light gets into the eye, which stops it getting damaged
• Reflex arc

  the passage of information in a reflex
• The neurones in reflex arcs go through the spinal cord or through an unconscious part of the brain
• When a stimulus is detected by receptors, impulses are sent along a sensory neurone to the CNS
• When the impulses reach a synapse between the sensory neurone and a relay neurone, they trigger chemicals to be released, which cause impulses to be sent along the relay neurone
• When the impulses reach a synapse between the relay neurone and a motor neurone, chemicals are released and cause impulses to be sent along the motor neurone
• The impulses travel along the motor neurone to the effector
• A muscle contracts or a gland secretes hormones in response
• Because you don't have to think about the response, a reflex is faster than normal responses