Final answer:
The somatic nervous system carries the pain message from Sandy's toe to her spinal cord, enabling a rapid response called a reflex arc.
Step-by-step explanation:
When Sandy scalded her toe in a tub of hot water, the pain message was carried to her spinal cord by the somatic nervous system. The somatic nervous system is responsible for our conscious perception of the environment and for our voluntary responses to that perception through the control of skeletal muscles.
It includes sensory neurons that receive input from environmental stimuli like temperature and pain. When these sensory neurons in the skin detect extreme temperatures, they trigger an action potential that travels to the spinal cord, where it can directly activate motor neurons without the need for the brain to process the information. This rapid process forms a reflex arc, which allows for a quicker response to avoid or minimize tissue damage.