The cerebrum (pl.: cerebra), telencephalon or endbrain is the largest part of the brain, containing the cerebral cortex (of the two cerebral hemispheres) as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. In the human brain, the cerebrum is the uppermost region of the central nervous system. The cerebrum develops prenatally from the forebrain (prosencephalon). In mammals, the dorsal telencephalon, or pallium, develops into the cerebral cortex, and the ventral telencephalon, or subpallium, becomes the basal ganglia. The cerebrum is also divided into approximately symmetric left and right cerebral hemispheres. With the assistance of the cerebellum, the cerebrum controls all voluntary actions in the human body.
Structure
The cerebrum is the largest part of the brain. Depending upon the position of the animal, it lies either in front or on top of the brainstem. In humans, the cerebrum is the largest and best-developed of the five major divisions of the brain. The cerebrum is made up of the two cerebral hemispheres and their cerebral cortices (the outer layers of grey matter), and the underlying regions of white matter. Its subcortical structures include the hippocampus, basal ganglia and olfactory bulb. The cerebrum consists of two C-shaped cerebral hemispheres, separated from each other by a deep fissure called the longitudinal fissure.
Cerebral cortex
The cerebral cortex, the outer layer of grey matter of the cerebrum, is found only in mammals. In larger mammals, including humans, the surface of the cerebral cortex folds to create gyri (ridges) and sulci (furrows) which increase the surface area. The cerebral cortex is generally classified into four lobes: the frontal, parietal, occipital and temporal lobes. The lobes are classified based on their overlying neurocranial bones. A smaller lobe is the insular lobe, a part of the cerebral cortex folded deep within the lateral sulcus that separates the temporal lobe from the parietal and frontal lobes, is located within each hemisphere of the mammalian brain.
Cerebral hemispheres The cerebrum is divided by the medial longitudinal fissure into two cerebral hemispheres, the right and the left. The cerebrum is contralaterally organized, i.e., the right hemisphere controls and processes signals (predominantly) from the left side of the body, while the left hemisphere controls and processes signals (predominantly) from the right side of the body. According to current knowledge, this is due to an axial twist that occurs in the early embryo. There is a strong but not complete bilateral symmetry between the hemispheres, while lateralization tends to increase with increasing brain size. The lateralization of brain function looks at the known and possible differences between the two.
Development In the developing vertebrate embryo, the neural tube is subdivided into four unseparated sections which then develop further into distinct regions of the central nervous system; these are the prosencephalon (forebrain), the mesencephalon (midbrain) the rhombencephalon (hindbrain) and the spinal cord. The prosencephalon develops further into the telencephalon and the diencephalon. The dorsal telencephalon gives rise to the pallium (cerebral cortex in mammals and reptiles) and the ventral telencephalon generates the basal ganglia. The diencephalon develops into the thalamus and hypothalamus, including the optic vesicles (future retina). The dorsal telencephalon then forms two lateral telencephalic vesicles, separated by the midline, which develop into the left and right cerebral hemispheres. Birds and fish have a dorsal telencephalon, like all vertebrates, but it is generally unlayered and therefore not considered a cerebral cortex. Only a layered cytoarchitecture can be considered a cortex.
Functions Note: As the cerebrum is a gross division with many subdivisions and sub-regions, it is important to state that this section lists only functions that the cerebrum as a whole serves. (See main articles on cerebral cortex and basal ganglia for more information.) The cerebrum is a major part of the brain, controlling emotions, hearing, vision, personality and much more. It controls all precision of voluntary actions, and it functions as the center of sensory perception, memory, thoughts and judgement; the cerebrum also functions as the center of voluntary motor activities.
Motor functions Upper motor neurons in the primary motor cortex which is located in the frontal lobe, send their axons to the brainstem and spinal cord to synapse on the lower motor neurons, which innervate the muscles. Through this connection signals from the Cerebrum control voluntary movements of the body. Damage to upper motor neurons can lead to lesions called upper motor neuron lesions. These lesions result in muscle weakness, spasticity, hyperreflexia, and Babinski sign.
Sensory processing The cerebrum takes in information from the senses and combines it, so the brain can understand the world as one picture. The main sensory areas notice basic details, while nearby areas put the information together and explain it.
Visual – The main visual area (V1) in the occipital lobe notices edges, colors, and movement. Nearby areas (V2–V5) help the brain recognize objects and faces. Auditory – The main hearing area in the upper temporal lobe senses the pitch and loudness of sounds. Nearby areas then help the brain process more complex sounds like speech and music. Somatosensory The main touch area in the parietal lobe maps feelings like touch, pain, temperature, and body position. Each body part has a matching area in the brain, and nearby regions help with spatial awareness and using objects. Gustatory The brain senses taste in the insula and frontal areas, then sends this information to the orbitofrontal cortex, where flavors are combined and understood. Multisensory integration Areas in the parietal and temporal lobes combine information from different senses to guide how we see, hear, and act. Lesions Damage in these areas can cause problems like loss of part of vision, trouble hearing, not recognizing objects by touch, or ignoring one side of space.
Olfaction
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