Nervous and Endocrine Systems

Each hemisphere controls the opposite side of the body. For example, theright hemisphere of your brain processes all of the stimuli received by your lefthand. Similarly, the left side of your brain controls the muscles that kick yourright leg. When the spinal cord brings a signal from the body, the signalcrosses over to the opposite hemisphere in the corpus callosum. The corpuscallosum is a thick band of nerves that connects the two hemispheres.The outer layer of the cerebrum, called the cerebral cortex, interpretsinformation from your sensory organs and generates responses. The cerebralcortex is about as thick as a pencil. Yet its size is deceptive because its folds giveit a larger surface area than you might expect. If the cerebral cortex wereunfolded, it would cover a typical classroom desk. This surface area is largeenough to hold more than 10 billion neurons.The neurons in the cerebral cortex are arranged in groups that worktogether to perform specific tasks. For example, movement is initiated by anarea of the brain called the motor cortex, and the sense of touch is received bythe sensory cortex. Scientists divide the cerebral cortex into different areas, orlobes, based on function. Each hemisphere of the human brain can be dividedinto four lobes—frontal, parietal, occipital, and temporal. The lobes and thecortical areas they contain are shown in FIGURE 29.10.FIGURE 29.10 Lobes of the BrainThe various areas of the cerebral cortex process different types of information.FRONTAL LOBEPersonality, reasoning, andjudgment are controlled inthe frontal lobe. It also coordinatesvoluntary movementand speech production.motor cortex(movement)sensory cortex(touch)PARIETAL LOBEThe sensory cortex, which interprets andcoordinates information regarding thesense of touch, is contained in this lobe.multisensoryinformationplanningspeech productionhearingvision(entire lobe)TEMPORAL LOBESpeech interpretation and hearing arefunctions carried out by the temporallobe. It also plays a role in memory.speechinterpretationOCCIPITAL LOBEVisual information isprocessed in this lobe.These scans of an actual brain(right) show which part of thebrain is most active while a persondoes different activities.1 2 3Apply Using the illustrationas a guide, determine whattype of information eachscanned brain is processing.Chapter 29: Nervous and Endocrine Systems 887