Final answer:
The sensation of touch is blocked from signaling to the brain through a pathway called the reflex arc.
Step-by-step explanation:
When you stick your hand in a bucket of ice, it grows numb after a while because of the process of neuronal signaling. The sensation of touch is blocked from signaling to the brain through a pathway called the reflex arc. In this pathway, the sensory neurons in your hand send signals to the spinal cord rather than the brain. The spinal cord then immediately activates motor neurons that cause your hand to withdraw from the cold stimulus, bypassing the brain and providing a rapid protective response.