What is a reflex?
Reflexes are automatic reactions that take place without your needing to think about them. If you prick you finger, you jerk your arm away instantly, even before your brain is aware that some damage has taken place. These reflexes take place in the spinal cord, where instructions are given to the muscles to pull your arm away as soon as the nerves have detected pain or damage. Reflexes also take place inside the body, maintaining normal conditions. A reflex starts the flow of digestive juices as soon as food enters the stomach. Another reflex causes a cough if you inhale a piece of fluff, or a blink when you get dirt in your eye.
Do nerve impulses travel straight through the nervous system?
It takes more than one nerve impulse to fire off another neurone. Each neurone receives messages saying ‘Fire’ and ‘Don’t fire’, and it will only fire off the nerve impulse if it gets more instructions to fire than to stop firing. It works a bit like the principle of voting, where a large number of ‘votes’ are needed in order for a message to be passed on.
Which are the longest nerve fibres?
The nerve fibres than run down into the leg are the longest cells in the whole body. They can be up one metre long.
