basic into to neuro...
I don't think that this is the place to talk about neuroscience.
But basically, whenever you do something, there are these gates that open and close letting different ions in and out of tissues (usually Na, Ca, K, Cl). Since ions are charged differently, there is a potential difference created between the membranes (due to charge difference). When there is some sort of stimuli (i.e. confusion, distraction, surprise): various gates start to open in different places. Such openings release and take in oppositely charged ions varying the EMF (electro-motive-force) thus sending an impulse down (either to or from the brain, depending on which nervous system you are talking about). When the impulse reaches your motor neurons, those control your organs or any place with muscles that make a specific part of your body move. So, depending on where the signal is sent (i.e. specific part of a brain), a person reacts differently.
These neuro-transmissions propagate from one neuron (basic unit of the nervous system) to the next in a waveform. The propagation opens many gates successively until a threshold is reached. At threshold, the impulse can fire. Until the threshold is reached, no impulse can fire (no matter how frequent the signal is sent). For example if your fingers are very unsensitive (low neuron number basically), and if you touch a hot stove, you will not feel hot but the fingers will keep burning without you recognizing it by touch.
There are techniques to control various transmissions physically through concentration and various techniques (i.e. tricking a lie-detector test - remember Seagal in Above the Law ... :=)