Neurons consist of three parts: the cell body, dendrites, and the axon. All sensations, movements, thoughts, memories, and feelings are the result of signals that pass through neurons. The brain and the rest of the nervous system are composed of many different types of cells, but the primary functional unit is a cell called the neuron. Parkinson’s disease, which results in tremors, rigidity, and a stiff, shuffling walk, is a disease of nerve cells that lead into the basal ganglia.
They are responsible for initiating and integrating movements. The basal ganglia (not shown) are clusters of nerve cells surrounding the thalamus. This tiny nub acts as a memory indexer-sending memories out to the appropriate part of the cerebral hemisphere for long-term storage and retrieving them when necessary. Near the hypothalamus lies the thalamus, a major clearinghouse for information going to and from the spinal cord and the cerebrum.Īn arching tract of nerve cells leads from the hypothalamus and the thalamus to the hippocampus. The hypothalamus is also an important emotional center, controlling the molecules that make you feel exhilarated, angry, or unhappy. It wakes you up in the morning, and gets the adrenaline flowing during a test or job interview. The hypothalamus, about the size of a pearl, directs a multitude of important functions. Like the lobes in the cerebral hemispheres, the structures described below come in pairs: each is duplicated in the opposite half of the brain. These structures not only determine our emotional state, but they also modify our perceptions and responses depending on that state, and allow us to initiate movements that you make without thinking about them. The Inner Brainĭeep within the brain, hidden from view, lie structures that are the gatekeepers between the spinal cord and the cerebral hemispheres. Other parts of this lobe seem to integrate memories and sensations of taste, sound, sight, and touch. The underside of each temporal lobe plays a crucial role in forming and retrieving memories, including those associated with music. At the top of each temporal lobe is an area responsible for receiving information from the ears. Whether you appreciate symphonies or rock music, your brain responds through the activity of these lobes. The last lobes on our tour of the cerebral hemispheres are the temporal lobes, which lie in front of the visual areas and nest under the parietal and frontal lobes. The folds in the brain add to its surface area and therefore increase the amount of gray matter and the quantity of information that can be processed. The cortex is gray because nerves in this area lack the insulation that makes most other parts of the brain appear to be white. When people talk about "gray matter" in the brain they are talking about this thin rind. Most of the actual information processing in the brain takes place in the cerebral cortex. It is called the cortex, from the Latin word for bark. The Cerebral CortexĬoating the surface of the cerebrum and the cerebellum is a vital layer of tissue the thickness of a stack of two or three dimes. For example, a stroke in the right hemisphere of the brain can leave the left arm and leg paralyzed. When one side of the brain is damaged, the opposite side of the body is affected. This means that the right cerebral hemisphere primarily controls the left side of the body, and the left hemisphere primarily controls the right side. For instance, the ability to form words seems to lie primarily in the left hemisphere, while the right hemisphere seems to control many abstract reasoning skills.įor some as-yet-unknown reason, nearly all of the signals from the brain to the body and vice-versa cross over on their way to and from the brain.
Although the two hemispheres seem to be mirror images of each other, they are different. Despite the split, the two cerebral hemispheres communicate with each other through a thick tract of nerve fibers that lies at the base of this fissure. The cerebrum is split into two halves (hemispheres) by a deep fissure. It allows you to recognize friends, read books, and play games.
It holds your memories, allows you to plan, enables you to imagine and think.
The cerebrum sits at the topmost part of the brain and is the source of intellectual activities. When people see pictures of the brain it is usually the cerebrum that they notice.
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