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Which structures connect the cerebrum to the spinal cord in the brainstem?

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Diagram comparing action potential conduction in myelinated and unmyelinated axons, showing a neuron with labeled cell body, myelin sheath, nodes of Ranvier, and the flow of electrical signals along each type of axon. — nervous system In a myelinated axon, the myelin sheath prevents the local current (small black arrows) from flowing across the membrane. This forces the current to travel down the nerve fibre to the unmyelinated nodes of Ranvier, which have a high concentration of ion channels. Upon stimulation, these ion channels propagate the action potential (large green arrows) to the next node. Thus, the action potential jumps along the fibre as it is regenerated at each node, a process called saltatory conduction. In an unmyelinated axon, the action potential is propagated along the entire membrane, fading as it diffuses back through the membrane to the original depolarized region.

The brainstem serves as the primary communication pathway between the cerebrum and the spinal cord. Anatomically, it is composed of three main sections that facilitate this connection:1

Midbrain (mesencephalon): The uppermost section of the brainstem, located directly beneath the diencephalon.21
Pons (metencephalon): The middle section, which connects the midbrain to the medulla oblongata.231
Medulla oblongata (myelencephalon): The lowest portion of the brainstem, which is continuous with the spinal cord at the base of the skull.231

Nearly all nerve pathways carrying information to and from the cerebrum pass through these regions via tracts, such as the corticospinal tract, which transmits motor commands from the cerebral cortex to the spinal cord.314