A good example of how the various components of the nervous system come together is the reflex arc. A reflex is a very specific response to a very specific stimulus that involves only neurons in the spinal cord and peripheral nerves. Let us consider the reflex that occurs when you touch something sharp. The pain receptors in your skin are activated and carry the pain message to the spinal cord on a sensory neuron. The axon terminal of the sensory nerve synapses in the gray matter of the spinal cord where the signal is interpreted. The neurons in the spinal cord then send a motor signal to your arm to withdraw from the painful stimulus. This entire pathway takes only milliseconds and effectively prevents you from damaging your finger. This is a particularly simple example because the generation of the motor signal occurs in the spinal cord and not in the brain. The brain would eventually receive information about what occurred, but the information would not be processed by the brain until after the signal had already been sent to the muscles of the arm to contract and withdraw the finger.
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