Reflexes

• Reaction times experiment

  1. Grab a 30cm ruler
  2. One person hold it at the top with 2 fingers
  3. Position your index and thumb right at the 0cm
  4. Unannounced, the person at the top drops it
  5. Other person tries to catch it

  Independent - person catching ruler

  Dependent - distance ruler was caught at (mm)
• This experiment is an example of a voluntary response
• The reaction of catching the ruler is under conscious control by the brain
• There are some reactions that are NOT under conscious control and they happen without us thinking...these are called reflexes
• Reflexes are fast, protective and automatic responses to stimuli
• Examples of reflexes are the:

  • Knee jerk - allows you to balance
  • Pupil jerk
  • Withdrawing your hand from a hot surface
• Reflex arcs reduce the time between detecting a stimulus and responding to it
• It is quicker because the information from the stimulus is not sent to the brain to process first before the effector is activated.
• If you touch something really hot, your hand is removed before your feel any pain
• Your brain still receives the information but with a slight delay.
• We also have cranial reflex arcs which are reflex arcs that have the relay neurone in the brain and not in the spinal cord.

  • Pupil reflex
• Reflex arc:

  A) stimulus

  B) receptor cell

  C) muscle (effector)