Cerebrum

Eva Rudolf-Müller is a freelance writer in the medical team. She studied human medicine and newspaper sciences and has repeatedly worked in both areas - as a doctor in the clinic, as a reviewer, and as a medical journalist for various specialist journals. She is currently working in online journalism, where a wide range of medicine is offered to everyone.

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The cerebrum (cerebrum, endbrain or telencephalon) make up the largest part of the brain. Its division into two hemispheres is reflected on a functional level - each side has specific tasks. Different functions can also be seen in the division of the cerebrum into different brain lobes. Read everything important about the cerebrum: function, division into different brain regions and bars, brain diseases and damage in this area!

What is the cerebrum?

The cerebrum (cerebrum) makes up the main part of the human brain. It consists of a right and a left half (hemisphere), both of which are connected to one another by a beam (corpus callosum). Apart from the bar, there are other (smaller) connections (commissures) between the two halves of the brain.

External structure of the cerebrum

The two cerebral hemispheres can each be divided into four lobes:

• Frontal lobe or frontal lobe (lobe frontalis)
• Parietal lobe (parietal lobe)
• Temporal lobe or temporal lobe (lobe temporalis)
• Occipital lobe or occipital lobe (lobus occipitalis)

The surface of the two halves of the cerebrum is furrowed like a walnut and therefore significantly enlarged. The numerous cerebral convolutions (gyri) are separated from one another by furrows (sulci).

Internal structure of the cerebrum

The cerebrum is divided into an outer part (cortex or cortex cerebri, gray matter) and an inner part (marrow, white matter).

The cerebral cortex is between two and five millimeters thick. It consists of the isocortex (or neocortex) and the underlying allocortex. The isocortex has six layers and makes up about 90 percent of the cerebral cortex. The Allocortex is historically older and has a three-layer structure. The evolutionarily oldest part of the allocortex is called the paleocortex (paleocortex). Together with the somewhat younger archicortex, it forms the allocortex.

The cerebral cortex consists of the cell bodies of billions of nerve cells (including pyramidal cells) and glial cells. The nerve cells have long axons in all directions. The medulla of the cerebrum consists of these nerve cell processes that enable communication with cells that are far away.

What is the function of the cerebrum?

The cerebrum is the supreme authority of the central nervous system. As a communication center, it connects all of our organs, organ systems and tissues with one another and coordinates them with one another. Stimuli from both the environment and the interior of our organism are received via receptors, passed on to the brain via ascending nerve pathways and then assessed and processed in the cerebrum and cerebral cortex. Depending on the type of stimulus, a response occurs in the form of stimuli that are given to the periphery, internal organs and organ systems via descending nerve tracts.

However, not all stimuli reach the cerebral cortex. Some information is processed very quickly in "lower" brain regions without reaching consciousness. For example, the central breathing regulation takes place in the medulla oblongata (elongated spinal cord or posterior brain).

Each half of the cerebrum is specialized in certain tasks: in the left areas of the cerebrum language and logic are usually located, in the right cerebral areas creativity and the sense of direction.

Homunculus (brain)

The cerebral cortex has various motor and somatosensitive areas that are assigned to specific body sections. Neighboring body parts are "mapped" to neighboring areas of the brain. This results in the model of a small, distorted human being, called a homunculus.

The function of different areas of the cerebrum

The neocortex houses, among other things, the ability to learn, speak and think, as well as consciousness and memory.

In the frontal lobe (frontal lobe) are the centers for voluntary movements and for the control and coordination of vegetative, affective and mental functions. The muscles that are important for speaking are represented in the motor language center (Broca's area) - in the left hemisphere for right-handers and in the right hemisphere for left-handers. The center for the movements of the eye muscles is also located in the frontal lobe.

In the parietal lobe or parietal lobe of the cerebrum is the body feeling sphere, represented by sensitive pathways that come from the skin and muscles and run through the thalamus into the primary, sensitive cortical areas of the parietal lobe. In secondary sensitive bark fields, memories of sensations that arose in the primary bark fields are stored.

The primary auditory center, the end of the auditory pathway, is located on the outer surface of the temple lobe. The secondary hearing center, the acoustic memory center, connects to the rear. Some sections of the hearing center scan the constant flood of noise that flows through the ear into the brain for familiar ones and classify them accordingly.

The Wernicke area is located in the temporal lobe and in part also in the parietal lobe, which is particularly important for understanding language. The Wernicke and Broca areas form the language center in the brain.

The visual cortex is located in the occipital lobe and is divided into a primary and a secondary visual center. Optical signals arrive here via the visual pathway, are processed and interpreted.Optical memory images are stored in the secondary visual center.

Where is the cerebrum located?

The cerebrum lies under the roof of the skull. The frontal lobe lies in the anterior cranial fossa, the temporal lobe in the middle cranial fossa.

What problems can the cerebrum cause?

Diseases and injuries in the cerebrum can have various consequences, depending on where in the cerebrum and how severe the damage is.

An irritation of the motor centers in the frontal lobe causes cramps (cortical epilepsy), a destruction of these centers initially leads to a paralysis of the muscles on the other side of the body (hemiplegia). Later on, neighboring cerebral fields and / or those on the opposite side can take over the function.

If secondary motor cortical fields in the frontal lobe are destroyed, the ability to perform purposeful movements acquired in the course of life disappears. Although the primary centers are intact and there is no muscle paralysis, those affected cannot speak (motor aphasia - Broca's aphasia) and cannot write (agraphia).

If Broca's area is damaged, the patient can usually still understand language, but has difficulty forming words and sentences himself. In milder cases, those affected can still communicate in a staccato telegram style.

If the primary, sensitive cortical areas of the parietal lobe are damaged, anesthesia and insensitivity result. Injuries to the secondary, sensitive areas of the cortex cause agnosia - the inability to recognize objects by touching them. Disturbances on the left side, in which the reading center is located with a reminder of the meaning of characters, lead to the inability to read (alexia).

If the hearing center in the temporal lobe is damaged, so-called cortical deafness develops. A one-sided, total disturbance is enough to cause deafness in both ears. Because in order to be able to hear, the auditory pathways of both ears to the auditory cortex in the two hemispheres of the cerebrum must be intact. Injuries or cerebral hemorrhages in this region mean that the patient can barely decipher language. He talks like a waterfall, but his flood of words is confused and incomprehensible.

A disruption of the secondary hearing center in the temporal lobe of the cerebrum means that earlier impressions are no longer remembered and words, noises, and music are no longer understood (so-called deafness of the soul).

The destruction of certain areas of the cerebral cortex in the area of ​​the visual center (brain) by a tumor or a stroke leads to visual field defects. If the visual cortex on both sides of the cerebrum is completely destroyed, what is known as cortical blindness results - those affected are blind even though their retina and visual pathway are intact. At best, they can still distinguish between light and dark and recognize movement stimuli.

When the secondary visual center (brain) in the occipital lobe in the cerebrum is destroyed, soul blindness results. Those affected cannot recognize objects again because the memory has disappeared and a comparison with earlier visual impressions is no longer possible.

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