for example when you are driving a car and a person comes up fast infront of you, your brain tells you to break but you

Question: for example when you are driving a car and a person comes up fast infront of you, your brain tells you to break but you always take a while to break after your brain has told you to do so, why?
- Keywords:
  brain,
  brake,
  car,
  drive,
  neuroscience
Asked by calvis to Mike, Pip, Tianfu, Tim, Tom on 27 Jun 2012.
- Tim Stephens answered on 27 Jun 2012:
  
  Your brain commands your body with electrical signals. It takes a short amount of time for these signals to get from your brain to the part that has to move, so there’s a short delay before your foot goes onto the brake pedal.
- Tom Lister answered on 27 Jun 2012:
  
  A friend of mine was measuring reflex times as part of his PhD – it took about 0.25 miliseconds after he pushed against my foot for me to push back. That’s the time for the signal to go up my nerve to the bottom of my spinal cord and back. For your brain to work out what to do and then send the signal from your head to your foot must take longer than this. Part of this will be deciding whether or not it is worth stopping, so it’s very complex and your brain is amazingly quick!

Question: for example when you are driving a car and a person comes up fast infront of you, your brain tells you to break but you always take a while to break after your brain has told you to do so, why?