Brain Structures and their FunctionsThe central nervous system(CNS) is made of the brain and the spinal cord and the peripheral
nervous system(PNS) is made of nerves. and from the spinal cord to the rest of your body. Sensorynerves gather information from the environment, send that info to the spinalcord, which then speed the message to the brain. Motor neurons deliver the instructionsfrom the brain to the rest of your body. The brain is made of threemain parts: the forebrain, midbrain, and hindbrain. The forebrain consists ofthe cerebrum, thalamus, and hypothalamus (part of the limbic system). Themidbrain consists of the tectum and tegmentum. The hindbrain is made of thecerebellum, pons and medulla. Often the midbrain, pons, and medulla arereferred to together as the brainstem. The cerebrumor
cortex is the largest part of the human brain, associated with higher brainfunction such as thought and action. Essentially this makes the brain moreefficient, because it can increase the surface area of the brain and the amountof neurons within it. We will discuss the relevance of the degree of cortical folding(or gyrencephalization) later. Sometimes the right
hemisphere is associatedwith creativity and the left hemispheres is associated with logic abilities. Whitenerve fibers underneath carry signals between the nerve cells and other partsof the brain and body. The neocortex occupies thebulk of the cerebrum. Like the cerebellum, evolutionarily the structure israther old. The brain stem is made ofthe midbrain, pons, and medulla. The frontal,temporal, parietal, and occipital lobes cover the brain's surface; the insulais hidden beneath the temporal lobe (see Fig. 1: Function and Dysfunction ofthe Cerebral Lobes: Areas of the brain. ). Areas of the brain.Visual,tactile, and motor activities of the left side of the body are directedpredominately by the right hemisphere and vice versa. There are at least 4functionally distinct areas in the frontal lobes: the primary motor cortex inthe precentral gyrus (the most posterior part) and the medial, orbital, andlateral frontal areas (termed the prefrontal areas).The medialfrontal area is important in arousal and motivation. Because 90% of motorfibers from each hemisphere cross the midline in the brain stem, damage to themotor cortex of one hemisphere causes weakness or paralysis on the oppositeside of the body.The amount ofcortical space given to a body part varies; eg, the area of the cortex thatcontrols the hand is larger than the area that controls the shoulder. The mapof these parts is called the homunculus (“little person”).In the primarysomatosensory cortex, located in the anterior parietal lobes, all of thesomatosensory functions on one side of the body are controlled by thecontralateral side (on a homunculus—see Fig. 2: Function and Dysfunction of theCerebral Lobes: Homunculus. ). The nondominant parietal lobe integratesthe contralateral side of the body with its environment and is important forattention to space and for abilities such as drawing.Occipital lobe: The occipital lobe contains the primary visual cortex and visualassociation areas. Insula: The insulaintegrates sensory and autonomic information from the viscera. The insulaprocesses aspects of pain and temperature sensation and possibly taste.Plasticity(ability of an area of the brain to alter its function) is most prominent inthe developing brain.