As we have been building up a picture of the nerve impulse travelling on tube lines through undergound tunnels. We said that "When the myelin is removed from nerves as occurs in MS. The nerve impulse travels very slowly"
So that you can see this I attach some videos
So before you play videos below. At the bottom of the video is a picture of a nerve fibre (tube line) and the myelin sheaths (tube tunnels) are shown in blue. On the top you will see the nerve impulse in yellow (these are the passengers moving in and out of the nerve) this is the electrical activity of the nerve and you can see the extent of a positive verse negative electrical charge) and this jumps between the gaps in the myelin (see videos on nerve impulses).
So this is a video of an actual nerve firing (You may need to visit blog on a computer to see)
Now you have seen that and got a feel for the speed. Now look at what can happens in a demyelinated nerve. The impulse gets there but it occurs more slowly because the myelin is gone. (For those of you who want to know, this gets there because the sodium channels move from the Node of Ranvier along the nerve to keep the nerve firing, but because the myelin is gone the impulse can't jump across the Nodes of Ranvier).
Now a demyelinated nerve (You may need to visit blog on a computer to see)
If this nerve was controlling how you clench a hand, then maybe the cup falling from the table may hit the floor before you catch it. However, this could also speed up your reaction if the nerve above was inhibiting the action of the nerve controlling how fast you clench your hand.However, just remember that to keep the nerve impulse flowing it uses more of the nerves energy stores.