The endbrain that steers voluntary life
The cerebrum—also telencephalon or endbrain—is the brain’s largest division, wrapping cortex around hippocampus, basal ganglia, and olfactory bulb. In humans it crowns the CNS; with cerebellar help it drives every voluntary action. Mammalian cortex folds into gyri and sulci to multiply surface area.
Two C-shaped hemispheres carry outer grey cortices and inner white matter, parted by a deep fissure. Depending on species posture, the mass sits ahead of or atop the brainstem. Among five major brain divisions in humans, this one is both biggest and most elaborated—the hardware of planning, language-ready cortex, and memory circuits nested below the sheet.
Only mammals wear a true cerebral cortex. Larger brains, including ours, corrugate that sheet so ridges and furrows cram more grey into the skull. Four lobes—frontal, parietal, occipital, temporal—take names from overlying cranial bones; the insula folds deep in the lateral sulcus between temporal and parietal banks.
Wiring is crossed: the right hemisphere mainly handles signals from the left side of the body, and the left hemisphere the right. In the embryo the neural tube splits into forebrain, midbrain, hindbrain and spinal cord, and the forebrain then divides into telencephalon, which becomes the cerebrum, and diencephalon. Voluntary movement starts with upper motor neurons in the primary motor cortex of the frontal lobe, whose axons reach down to lower motor neurons in the brainstem and cord that drive the muscles; injury to those upper neurons produces upper motor neuron lesions. Sensation is assembled in layers. The primary visual area, V1, in the occipital lobe picks out edges, colour and motion, while V2 to V5 help recognise objects and faces. The upper temporal lobe registers pitch and loudness before neighbouring areas parse speech and music. A touch map in the parietal lobe gives each body part its own patch, taste is sensed in the insula and frontal areas before the orbitofrontal cortex combines flavours, and parietal and temporal zones merge the senses to guide action.
Source: Cerebrum
