Final answer:
The medulla oblongata is the bidirectional passageway for all tracts connecting the cerebrum and the spinal cord, playing a crucial role in signal transmission and control of vital functions.
Step-by-step explanation:
The bidirectional passageway for all tracts connecting the cerebrum and the spinal cord is the medulla oblongata. It is part of the brainstem which includes the midbrain, medulla oblongata, and the pons. The medulla oblongata connects the brain with the spinal cord, facilitating the relay of signals between the two, as well as controlling essential functions like breathing, blood pressure, and heart rate.
The corpus callosum, while an important structure for communication, is a thick fiber bundle that specifically connects the two cerebral hemispheres and is not the passageway for tracts between the cerebrum and spinal cord. The central canal, conversely, is the continuation of the spaces within the brain known as ventricles, where cerebrospinal fluid is found and is not responsible for connecting the cerebrum with the spinal cord in a functional sense.