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What are the three major divisions of the human brain?

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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 human brain is organized into three major developmental divisions: the forebrain, the midbrain, and the hindbrain.123

Forebrain: This region includes the cerebral hemispheres and the diencephalon (containing the thalamus and hypothalamus). It is central to complex cognitive activities, sensory integration, and voluntary motor control.23
Midbrain: In humans, this area is reduced in size compared to other vertebrates and serves primarily as a connecting link between the forebrain and the hindbrain.2
Hindbrain: Composed of the medulla oblongata, the pons, and the cerebellum, this division coordinates fundamental survival functions, including respiratory rhythm, motor activity, and sleep.12

While these three regions represent the primary developmental divisions, the adult brain is also frequently categorized by its functional structures: the cerebrum, the cerebellum, and the brainstem.2