Final answer:
The structure of the brain that rests upon the posterior cranial fossa is the cerebellum, essential for motor control and coordination.
Step-by-step explanation:
The structure of the brain that rests upon the posterior cranial fossa is the cerebellum. The posterior cranial fossa is the deepest part of the cranial cavity and is bounded anteriorly by the petrous ridges and posteriorly by the occipital bone. It contains the cerebellum, which plays a vital role in motor control and coordination of movement. This fossa also houses the foramen magnum, through which the spinal cord passes.
Responsibilities of the cerebellum include the fine-tuning of motor commands to produce smooth and coordinated muscular activity. This is crucial when performing tasks like catching a ball, where the head and eyes must be precisely coordinated, an activity involving not just the cerebellum but also structures like the superior colliculus.