What Happens When Your Foot Goes to Sleep?
Our muscles, as we call the bands of flesh which move the different parts of our bodies, can move only when directed to do so by our motor nerves, which may be roughly described as telegraph wires between our nerve centres and our muscles. Before the mysterious order is sent from the nerve centre along the motor nerve to the muscle directing it to move, the nerve centre has to receive a message from another and quite different nerve called the sensory nerve. Scientific men call this reflex action.
From the brain, or from the spinal cord (the big nerve which runs up the backbone) motor and sensory nerves are connected to every part of the body. If a motor nerve is cut, we lose all control of the part of the body it serves, but sensation remains. If a sensory nerve is cut, we lose sensation in the part which it serves, but retain the power of movement. If both are cut, we lose both sensation and the power to move.
Fortunately, serious damage to a nerve does not often occur, but we sometimes experience what undue pressure on a nerve can do. If we sit on a chair so that a sharp edge presses the nerves of our leg, we may easily find that our foot ‘goes to sleep.” What has happened is that pressure has affected the nerves serving the foot, and by compressing their fibres has made them incapable of transmitting impulses. On attempting to rise we can not feel our foot because the sensory nerve has been pressed, and we can not direct the foot to act because the motor nerve has been pressed. The foot is numb. Gradually the nerves recover as the pressure is removed, and we get the tingling we call “pins and needles.”
