Final answer:
Mairs' clumsiness and tripping were due to deficiencies in her spinal cord and cerebellum, belonging to the central nervous system (CNS), which controls coordinated movements.
Step-by-step explanation:
When Mairs consulted a doctor about her clumsiness and tripping, the tests indicated deficiencies in her spinal cord and cerebellum. These structures are responsible for controlling coordinated movements, and they belong to the functional division of the nervous system known as the central nervous system (CNS). The CNS is crucial for interpreting sensory information and responding with motor actions, which in Mairs' case, were affected leading to her symptoms.