The brain (technically: cerebrum or encephalon) is the control center of the body, consisting of nerve tissue, in which information from inside the body is integrated with information from the outside world and processed. Together with the spinal cord, it forms the central nervous system (CNS).
What is the brain?
Brain cells are made up of dendrites and axons, at the end of which synapses can form. The number of synapses plays a more significant role in information exchange than the number of neurons. Click to enlarge. The human brain is the part of the central nervous system located in the skull. The transition to the spinal cord is marked by the pyramidal tract junction at the level of the large occipital hole (foramen magnum) at the base of the skull. The brain of an adult male weighs an average of 1400 g, that of an adult female an average of 1300 g for the same body size. According to current estimates, the brain consists of about 100 billion nerve cells and about as many glial cells again.
Anatomy and structure
Even at first glance, the division of the brain into two hemispheres is visible. The cerebral hemispheres are connected by several commissures. According to its evolutionary history, the brain is divided into three parts:
The evolutionarily oldest part is the rhomboid brain, consisting of the medulla oblongata, the bridge and the cerebellum. This is followed by the midbrain. The youngest part is the forebrain, which can be further subdivided into the diencephalon and the cerebrum. Schematic representation of the functional areas of the human brain. Click to enlarge. The brain is surrounded by protective meninges. The cerebral cortex is heavily furrowed for the purpose of surface enlargement. The cortex is usually divided into 5 lobes: frontal lobe, parietal lobe, temporal lobe, occipital lobe and insular lobe. In the brain itself, gray and white matter can be distinguished: Gray matter contains a high number of cell bodies. It occurs mainly superficially in the cortex, and in the interior of the brain only islands of gray matter are found as nuclei or nets. Otherwise, white matter predominates in the interior, consisting mainly of nerve cell processes. In addition, there is a cavity system of 4 ventricles in the interior of the brain. These are filled with cerebrospinal fluid, which performs cushioning, immunologic, and signaling functions.
Functions and Tasks
Schematic diagram showing the anatomy and structure of the brain. Click to enlarge. The brain is a highly complex organ that performs a wide variety of tasks. It controls basic autonomic functions as well as peak cognitive performance. In the developmentally older sections, basal functions such as heart rate, respiration, sweat secretion and vigilance are controlled. An interplay of older and younger structures is necessary for the production of emotions, natural rhythms and memory functions. In the brain, the sensory impressions of all senses are processed and integrated so that perceptions and sensory sensations are created. Especially the sense of sight, which is very well developed in humans, occupies considerable parts of the cerebral cortex. The motor system within the brain enables the control and planning of muscle activity. Without the motor brain services, only a few reflex movements are possible via the spinal cord. The cerebrum is also considered the seat of human personality and intelligence. To perform its extensive services, the brain requires a lot of energy: at rest, it is responsible for 15-20% of our energy consumption.
Diseases
The spectrum of possible brain diseases is extremely wide. The first sign of brain disease is usually pain or dysfunction. A very common clinical picture in industrialized nations is stroke, in which brain tissue is no longer supplied with sufficient blood due to vascular occlusion or rupture. Nerve cells react very sensitively to a lack of oxygen and perish irretrievably after just a few minutes. Also common are epilepsies, which result from uncontrolled mass discharges of neurons. Cancer can affect the brain either primarily in the form of brain tumors or secondarily through brain metastases. Inflammatory brain diseases (encephalopathies) are caused by viruses, bacteria, fungi or worms and often also affect the meninges in the form of meningitis.The etiology of multiple sclerosis, a chronic inflammatory disease in which the myelin sheaths of the CNS degenerate, is still not understood. Degenerative brain diseases that are not yet fully understood also include Alzheimer’s dementia, Huntington’s disease, and Parkinson’s disease. Craniocerebral trauma can end benignly with a mild concussion, but it can also result in contusions, hemorrhages, and a lethal increase in intracranial pressure. Irreversible brain failure is referred to as brain death and – ethically controversial – is used as the definition of death.
Typical and common disorders
- Dementia
- Creutzfeldt-Jakob disease
- Memory gaps
- Brain hemorrhage
- Meningitis
