Final answer:
When hot chocolate is dumped on your lap, the sensory neurons in your skin send signals to the central nervous system. The CNS interprets the signals as being from a dangerous heat source and sends motor responses to withdraw the affected area from the hot chocolate.
Step-by-step explanation:
When hot chocolate is dumped on your lap, the sensory neurons in your skin detect the heat and send signals to the central nervous system (CNS) which includes the brain and spinal cord.
The CNS interprets the signals as being from a dangerous heat source and sends motor responses to the muscles to withdraw the affected area from the hot chocolate. The muscles then contract and move the affected area away from the source of heat, resulting in a quick reflexive response.