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Brain: structure and function

by Josephine Andrews
Published: Last Updated on 329 views

The brain (encephalon) is the control center of our body. It consists of a plethora of brain cells that are linked together. The brain is very metabolically active and therefore needs a lot of oxygen and blood sugar (glucose). It reacts extremely sensitively to a lack of supply. Read everything you need to know about: What is the anatomy of the brain like? How does the brain work? What is the storage capacity (brain)? What are the main diseases and injuries?

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 innumerable nerve cells, which are connected to and control the organism via nerve tracts leading in and out.

The brain volume (human) is about 20 to 22 grams per kilogram of body mass. The weight (brain) accounts for about 3 percent of body weight at 1.5 to 2 kilograms.

How many brain cells does a human have?

A human being has approximately 100 billion brain cells that make up the central nervous system, our brain, and are interconnected. The number of these links 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 these cells have and how they are structured in the article Glial cells .

meninges

The brain is surrounded by three meninges: dura mater, arachnoid and pia mater. You can find out more about everything important about the three protective covers and their function in the article Meninges .

Brain Structure: Five Sections

The human brain can be roughly divided into five sections:

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 post Cerebrum .

diencephalon

The diencephalon consists, among other things, of the thalamus and the hypothalamus . You can read more information about the structure and function of the diencephalon in the article diencephalon .

The base of the brain is located in the lower area of ​​the skull and is more heavily modeled in accordance with the bony base of the skull . Here is the brainstem .

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 post.

midbrain (mesencephalon)

The mesencephalon is the smallest section of the brain. You can find out everything you need to know about its structure and function in the article Midbrain .

Medulla oblongata (myelencephalon)

The meyelencephalon, also known as the hindbrain, represents the transition between the brain and spinal cord. You can read more about this brain section in the article Medulla oblongata .

cerebellum

The cerebellum sits above the brainstem and below the two cerebral hemispheres. You can read more about its functions and anatomy in the article The cerebellum .

gray matter

The gray matter in the brain consists primarily of nerve cell bodies. The name comes from the fact that the nerve cells are pink in the living organism, but turn gray after its death. The cerebral cortex, the basal ganglia , the cerebellar cortex and the cranial nerve nuclei consist of gray matter. About 80 percent of the cerebral blood flow is necessary for the supply of the gray matter.

basal ganglia

The basal ganglia are a group of cerebral and diencephalic gray matter nuclei. You can read more about them and their functions in the article Basal ganglia .

white substance

In addition to the gray matter, there is also the 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

Twelve pairs of nerves originate in the brain and supply the head, neck and organs in the trunk. You can read more about these important nerve pathways in the article Cranial nerves .

The blood supply (brain)

About 800 milliliters of blood flows through the brain every minute . This amount can fluctuate slightly up to age 50, but decreases thereafter (along with oxygen and glucose consumption). The blood supply to the brain accounts for between 15 and 20 percent of the cardiac output.

The blood supply to the brain is always about the same in phases of sleep and wakefulness. Even with an increase in blood pressure, a drop in blood pressure, heavy physical exertion or even an irregular heartbeat , the blood flow to the brain hardly changes – except when the systolic blood pressure falls sharply (below 70 mmHg) or rises sharply (above 180mmHg).

Blood supply to the brain is provided by the right and left internal carotid arteries (internal carotid artery), which arise from the common carotid artery (common artery), and by the vertebral artery, which emerges from the vertebral bodies and enters the cranial cavity through the occipital foramen. These are closed by additional arteries to form a vascular ring (circulus arteriosus cerebri) that encompasses the base of the diencephalon.

This vascular ring ensures that the blood demand of the sensitive brain is always sufficient, even when there are fluctuations in the blood supply. The vascular ring and its branches lie between two meninges (the cobweb and the inner meninges) in the so-called subarachnoid space and are surrounded by liquor (cerebrospinal fluid), which protects the thin-walled vessels.

liquor

CSF is the fluid that protects the brain and spinal cord. You can read more about the cerebrospinal fluid in the article Liquor .

ventricular system

The brain has several cavities (brain chambers) in which CSF circulates and which together form the ventricular system. You can read more about this in the article ventricular system .

The blood-brain barrier

The sensitive tissue in the brain is shielded from harmful substances in the blood (such as toxins, pathogens, certain medications, etc.) by the blood-brain barrier . You can find out more about everything important about this protective mechanism in the article on the blood-brain barrier .

Energy expenditure (brain) and brain capacity

The energy consumption in the brain is extremely high. The brain accounts for almost a quarter of the body’s total energy requirements. The brain uses up to two-thirds of the amount of glucose that is ingested daily with food.

The brain capacity is significantly larger than what we actually use in everyday life. This means that a large part of our brain capacity is unused.

development of the brain

The embryonic development of the brain from the neural tube is characterized on the one hand by a particular growth in size and on the other hand by an uneven growth in thickness of the wall and particular kinks. As a result, the brain is divided into several sections at an early stage.

First of all, three successive sections (primary cerebral vesicles) develop from the brain system, which then form the forebrain, the midbrain and the hindbrain. In the further development, five further, secondary cerebral vesicles arise from this: The cerebrum and diencephalon develop from the forebrain. From the hindbrain arise the medulla oblongata, pons and cerebellum.

What is the function of the brain?

The functional areas of the brain are diverse. The brainstem, the oldest part of the brain in terms of evolutionary history, is responsible for the basic functions of life. It controls heart rate, blood pressure and respiration as well as reflexes such as blinking, swallowing or coughing.

The diencephalon has several sections, including the thalamus and the hypothalamus: sensory impressions are processed in the thalamus; The sleep-wake cycle, hunger and thirst, the perception of pain and temperature and the sex drive are controlled via the hypothalamus.

thalamus

You can find out everything you need to know about this important part of the midbrain, which is considered the “gateway to consciousness”, in the article Thalamus .

hypothalamus

You can read more about the structure and tasks of the hypothalamus in the article Hypothalamus .

pituitary

The pituitary gland is connected to the hypothalamus by a stalk. You can read more about the anatomy and function of this endocrine gland in the article Pituitary Gland .

The cerebellum coordinates our movements and balance and stores learned movements.

In the cerebrum there is language and logic on the one hand and creativity and a sense of direction on the other.

The ability to learn, speak and think as well as consciousness and memory are anchored in the cerebral cortex – the outer area of ​​the cerebrum . This is where the information from the sense organs comes together, is processed and finally stored in the memory.

limbic system

The limbic system regulates affect and drive behavior and its connections with vegetative organ functions. You can read more about this area of ​​the brain, which is very old in terms of evolutionary history, in the article Limbic system .

Two important sub-areas within the limbic system are the amygdala (almond core) and the hippocampus :

amygdala

You can find out what tasks the amygdala has in the article Amygdala .

hippocampus

The hippocampus is our brain’s working memory and the interface between short- and long-term memory. You can read more about this in the article Hippocampus .

memory

A very important function of the brain is memory – from ultra-short to short-term to long-term memory. You can read more about this in the article Memory .

How does the brain work?

Smooth functioning of all organs and tissues in the body and sensitive behavior are only possible if all organ functions are coordinated and controlled by a superordinate control authority and all information that the environment provides us with is recorded, processed and answered. This task is performed by our brain, the network of billions of nerve cells (neurons).

The brain cells are connected to each other by synapses, contact points between the cells. These contact points play an important role in processing the messages. Information from the body or the environment reaches the brain in the form of hormones via the blood or as electrical impulses from the sensory cells via nerve tracts. There they are evaluated and processed. In response, the brain sends out corresponding signals—for example, to muscles to move, to glands to produce and release secretions, or to sensory organs to respond to stimuli from the environment.

Where is the brain?

The brain is located in the bony skull , completely filling it and continuing through the occipital foramen as the spinal cord in the spine .

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 the body or from the outside) – although it is relatively well protected by the bony skull.

The mildest form of traumatic brain injury is a concussion . It is usually accompanied by unconsciousness lasting a few seconds to hours, but can also only consist of a brief twilight. Short gaps in memory of up to an hour are possible.

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.

Any head trauma—no matter how minor, such as bumping your head while getting out of a car—can cause an epidural hematoma. Here, bleeding occurs between the dura mater and the skull bone due to a ruptured vessel. The addictive bruise can cause clouded consciousness and hemiplegia within minutes to hours.

Subdural hematomas in the brain are bruises between the outer and middle meninges, ie between the dura mater and arachnoid membrane. They arise from torn bridging veins, usually in connection with a severe brain contusion.

An epileptic seizure that occurs before the age of 25 has its cause in early childhood brain damage. Seizures that occur later in life can be caused by tumors or other brain or cerebrovascular diseases.

Multiple sclerosis is an inflammatory disease of the central nervous system (brain and spinal cord) . This leads to focal dissolution of the myelin sheaths, the insulating layer of the nerve fibers. Nerve conduction is no longer possible without a myelinated sheath. Depending on the location, there are corresponding failures.

Brain tumors can occur at any age and can be benign or malignant.

stroke is an acute circulatory disorder in the brain . The sudden interruption of the oxygen supply causes the nerve cells in the affected brain area to die off.

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