What is the brain?
The brain (encephalon) is the part of the central nervous system that lies within and fills the bony skull. It consists of countless nerve cells that are connected to and control the organism via afferent and efferent nerve pathways.
The brain volume (human) is about 20 to 22 grams per kilogram of body mass. The weight (brain) makes up about three percent of the body weight with 1.5 to two kilograms.
A human being has about 100 billion brain cells that make up the central nervous system, our brain, and are interconnected. The number of these connections is estimated at 100 trillion.
Glial cells
The nerve cells in the brain are embedded in a supporting tissue of glial cells. You can read about the tasks of these cells and how they are structured in the article Glial Cells.
Cerebral membranes
Brain structure: Five sections
The human brain can be roughly divided into five sections:
- Cerebrum (telencephalon)
- Interbrain (Diencephalon)
- Midbrain (Mesencephalon)
- Cerebellum (cerebellum)
- Afterbrain (myelencephalon, medulla oblongata)
Cerebrum (Telencephalon)
The cerebrum is the largest and heaviest part of the brain and resembles a walnut kernel with its folds and furrows. Read more about its anatomy and function in the article Cerebrum.
Diencephalon (Interbrain)
In the lower skull region is the base of the brain, which – corresponding to the bony base of the skull – is more strongly modeled. This is where the brain stem is located.
Brainstem
The brainstem is the phylogenetically oldest part of the brain and consists of the midbrain, medulla oblongata and bridge (pons). Read more in the brainstem article.
Midbrain (Mesencephalon)
Medulla oblongata (Myelencephalon)
The meyelencephalon, also known as the afterbrain, represents the transition between the brain and the spinal cord. You can read more about this section of the brain in the article Medulla oblongata.
Cerebellum
Above the brain stem and below the two cerebral hemispheres sits the cerebellum. Read more about its functions and anatomy in the article Cerebellum.
Gray matter
Basal Ganglia
The basal ganglia are a group of cerebral and diencephalic gray matter nuclei. Read more about them and their functions in the article Basal ganglia.
White matter
In addition to gray matter, there is also white matter, which consists of the nerve cell processes, the nerve fibers (axons). The white matter is found in the medulla of the cerebrum and cerebellum.
Cranial nerves
The blood supply (brain)
The brain receives about 800 milliliters of blood per minute. This volume may vary slightly until age 50, but decreases thereafter (along with oxygen and glucose consumption). Between 15 and 20 percent of the cardiac output per minute is accounted for by the blood supply to the brain.
The blood supply to the brain is provided by the right and left internal carotid arteries, which arise from the common carotid artery, and by the vertebral artery, which comes from the vertebral bodies and enters the cranial cavity through the occipital orifice. Further arteries close these to form a vascular ring (circulus arteriosus cerebri) that encompasses the base of the diencephalon.
CSF
The cerebrospinal fluid is the fluid that surrounds the brain and also the spinal cord in a protective manner. Read more about cerebrospinal fluid in the article CSF.
Ventricular System
The brain has several cavities (cerebral ventricles) in which the cerebrospinal fluid circulates and which together form the ventricular system. Read more about this in the article Ventricular System.
The blood-brain barrier
Energy consumption (brain) and brain capacity
Energy consumption in the brain is enormous. Almost a quarter of the body’s total energy requirement is accounted for by the brain. Up to two-thirds of the glucose consumed daily with food is used by the brain.
The brain’s capacity is significantly greater than that which we actually use in everyday life. This means that a large part of our brain capacity is unused.
Development of the brain
Initially, three successive sections (primary cerebral vesicles) form from the brain anlage, which then form the forebrain, the midbrain and the rhombic brain. In further development, five additional, secondary brain vesicles develop from these: The cerebrum and diencephalon develop from the forebrain. The medulla oblongata, the bridge and the cerebellum emerge from the rhombus brain.
What is the function of the brain?
The diencephalon has several sections, including the thalamus and the hypothalamus: sensory impressions are processed in the thalamus; the hypothalamus controls the sleep-wake rhythm, hunger and thirst, the sensation of pain and temperature, and the sex drive.
Thalamus
You can learn everything important about this important part of the diencephalon, which is considered the “gateway to consciousness”, in the article Thalamus.
Hypothalamus
Pituitary gland
The pituitary gland is connected to the hypothalamus by a stalk. Read more about the anatomy and function of this hormonal gland in the article Pituitary gland.
The cerebellum coordinates our movements and balance and stores learned movements.
The cerebrum contains language and logic on the one hand, and creativity and sense of direction on the other.
Limbic System
The limbic system regulates affect and drive behavior and its links with vegetative organ functions. You can read more about this developmentally very old area of the brain in the article Limbic System.
Two important sub-areas within the limbic system are the amygdala (almond nucleus) and the hippocampus:
Amygdala
You can read about the functions of the amygdala in the article Amygdala.
Hippocampus
Memory
A very important function of the brain is memory – from ultra-short term to short term to long term memory. You can read more about this in the article Memory.
How does the brain work?
Where is the brain located?
The brain is located in the bony skull, fills it completely and continues through the occipital hole as the spinal cord in the spinal column.
What problems can the brain cause?
Since the brain is a very complex and highly sensitive system, it can be disturbed or damaged by various influences (from inside or outside the body) – although it is relatively well protected by the bony skull.
A more serious injury is a skull contusion, which means damage to the brain substance. The disturbance of consciousness can then last longer than an hour. Paralysis and epileptic seizures are also possible.
Subdural hematomas in the brain are effusions of blood between the outer and middle meninges, i.e., between the dura mater and the arachnoid. They arise from ruptured bridging veins, usually in association with more severe cerebral contusion.
An epileptic seizure that occurs before the age of 25 is caused by early childhood brain damage. Seizures occurring later in life may be due to tumors or other brain or cerebrovascular disease.
Tumors in the brain can occur at any age and can be benign and malignant.
A stroke is an acute circulatory disorder in the brain. The sudden interruption of the oxygen supply causes the nerve cells in the affected area of the brain to die.
