BRAIN: PARTS, FUNCTIONS AND DISEASES - NEUROPSYCHOLOGY - 2024

The encephalon is the highest and largest part of the central nervous system, located in the skull and with functions of conducting and integrating information, reasoning, judgment or control of behavior. It is divided into three different parts: the forebrain, the midbrain, and the rhombencephalon, also called the forebrain, middle, and hindbrain.

Each of these parts contains specific brain regions that perform different mental activities. On the other hand, the brain can be subdivided into three main regions: the forebrain, the middle and the hindbrain.

The brain is located in the center of the brain - central nervous system - and performs very diverse functions. Of all the functions it performs, the control of the body's activity and reception of information from inside and outside stands out.

In other words, the brain is in charge of associating the physical components with the psychological ones, as well as adapting the information from the brain with that which is received from the outside through the senses.

Parts of the brain

Human brain in sagittal section: 1. Anterior brain, 2. Telencephalon (indicated the frontal lobe, with attenuated vision of the temporal lobe), 3. Diencephalon, 4. Brainstem, 5 Mesencephalon, 6. Protuberance, 7. Medulla oblongata, 8. Cerebellum, 9. Spinal Cord. Source: Jmarchn, own work via Wikimedia Commons

The brain is a very large region, in fact, it is the most voluminous structure of the human brain. For this reason, it contains thousands of different regions within it.

At the macroscopic level, it is divided into three distinct parts: the forebrain, the midbrain, and the rhombencephalon.

- Forebrain or forebrain

The forebrain is the anterior portion of the brain. During the gestation of the embryo, this is one of the first regions to develop. Later, within the forebrain there are two regions that cover its structure: the telencephalon and the diencephalon.

Telencephalon

Telencephalon (red)

The telencephalon is the upper and most voluminous region of the forebrain. It represents the highest level of somatic and vegetative integration.

This region is different between amphibians and mammals. In the former, it is made up of highly developed olfactory bulbs, while in the latter it contains two cerebral hemispheres.

Within the telencephalon we find:

1. Occipital lobe: performs visual sensory operations.
2. Parietal lobe: processes sensitive and kinesic information.
3. Temporal lobe: performs auditory processes.
4. Frontal lobe: performs higher functions such as judgment, reasoning, perception, and motor control.
5. Striatum: receives information from the cerebral cortex and basal ganglia.
6. Rhinencephalus: brain region involved in smell.

Thus, the telencephalon contains multiple brain regions and performs multiple mental processes. The processing of information from the senses and other brain regions are the most important. But it also participates in more elaborate functions through the frontal lobe.

Diencephalon

Diencephalon (red)

The diencephalon is the other sub-region of the forebrain. It is located below the telencephalon and limits its lower part with the midbrain. This structure contains very important brain elements. The main ones are the thalamus and the hypothalamus.

Hypothalamus

Hypothalamus (orange)

It is a small organ. Forms the base of the thalamus, controls autonomous visceral functions and sexual urges. Likewise, it performs important activities in the regulation of appetite, thirst and sleep.

Thalamus

It is the most voluminous and important region of the diencephalon. Its main function is to collect information from all the senses, except smell. It is directly connected to the cerebral cortex and plays important roles in the development of emotions and feelings.

Subthalamus

This small region is located between the thalamus and the hypothalamus. It receives information from the cerebellum and the red nucleus, and it is composed mainly of gray matter.

Epithalamus

Above the thalamus is this structure, which comprises the pineal gland and the habenular nuclei. The epithalamus belongs to the limbic system and is responsible for producing melatonin.

Metathalamus

Above the epithalamus is the metathalamus, a structure that acts as a passageway for nerve impulses that circulate from the lower peduncle to the auditory cortex.

Third ventricle

Finally, in the uppermost part of the diencephalon, we find a ventricle that is responsible for cushioning craniocephalic blows, in order to protect the lower regions of the diencephalon.

- Midbrain or midbrain

Source: From Xtabay - Own work, via Wikimedia Commons

The midbrain or midbrain is the central part of the brain. It constitutes the upper structure of the brain stem and is responsible for joining the varolian bridge and the cerebellum with the diencephalon.

Within the midbrain we find three main regions:

1. Anterior: in this region we find the tuber cinereum and the posterior perforated substance. It is a small groove that has its origin in the ocular motor nerve.
2. Lateral: it is formed by the upper conjunctival arm and the optic band. Its functions are simply of connection between the tubers and the geniculate bodies.
3. Posterior: here are the four quadrigeminal tubers, rounded eminences divided into anterior and superior pairs that modulate visual reflexes, and posterior and inferior pairs that modulate auditory reflexes.

The main function of the midbrain is therefore to conduct motor impulses from the cerebral cortex to the brainstem bridge. Or what is the same, from the upper regions of the brain to the lower regions, so that these reach the muscles.

It primarily transmits sensory and reflex impulses, and connects the spinal cord with the thalamus.

- Rhombencephalon or hindbrain

Brain anatomy. Source: BruceBlaus via Wikimedia Commons

The hindbrain or hindbrain is the lower portion of the brain. It surrounds the fourth cerebral ventricle and limits its inferior part with the spinal cord.

It is made up of two main parts: the metancephalon which contains the cerebellum and pons, and the myelcephalon which contains the spinal cord.

Metancephalon

It is the second gallbladder of the brain, and forms the upper part of the rhombencephalon. It contains two main and highly important regions for brain function: the cerebellum and the pons.

1. Cerebellum: its main function is to integrate the sensory and motor pathways. It is a region filled with nerve connections that allow connection with the spinal cord and with the upper parts of the brain.
2. Protuberance: it is the portion of the brainstem that is located between the medulla oblongata and the midbrain. Its main function is similar to that of the cerebellum and is responsible for connecting the midbrain with the upper hemispheres of the brain.

Myncephalon

The myelencephalon is the lower part of the rhombencephalon. This region contains the medulla oblongata, a cone-shaped structure that transmits impulses from the spinal cord to the brain.

Features

The brain is made up of many different regions. In fact, its parts are differentiated based on their location, so that some are closer to the upper regions and others border the spinal cord.

The main function of many parts of the brain, such as the myelencephalon, the metancephalon, or the midbrain, is to carry information.

In this way, the lowermost region (the myelencephalon) collects information from the spinal cord, and subsequently these impulses are conducted by the posterior regions of the brain.

In this sense, one of the main functions of the brain is to collect information from the body (from the spinal cord) and lead it to higher regions of the brain (and vice versa).

This function is highly important since it is the mechanism that mammals have to integrate physical information with psychic information. Likewise, it allows the start-up of thousands of physiological processes.

On the other hand, in the brain regions (telencephalon and diencephalon) the information obtained is integrated and other mental processes are carried out. The regulation of hunger, thirst, sleep, sexual functioning and sensory stimuli are the most important activities.

Likewise, the brain also participates in more complex processes such as reasoning, judgment, the production of emotions and feelings, and the control of behavior.

Cell structure

In the brain we find two main types of cells: neurons and glial cells. Each one of them performs different functions, although glial cells are much more abundant in quantity than neurons.

Glial cells are cells of nervous tissue that perform auxiliary and complementary functions to neurons. In this way, these types of cells collaborate in neuronal transmission.

Neuron

In addition, glial cells are also responsible for activating the brain's information processing in the body. In this way, these types of cells allow the exchange of information between body and mind, which is why they are so abundant in the brain.

Unlike glial cells, neurons are capable of sending signals over long distances, which is why they are less abundant than glial cells. Neurons are responsible for transmitting neural information from one part of the brain to another, and allow the central nervous system to function.

Functioning

The functioning of the brain is produced by the action of the types of cells that we find inside: glial cells and neurons. Information is transmitted between different parts of the brain, and between the brain and the spinal cord. This transmission takes place through a long network of interconnected neurons.

The brain is adapted so that subtle changes in the neurotransmission mechanism elicit different responses. In this way, the performance varies depending on the type of signal that is perceived.

For example, upon the perception of a burn stimulus in the hand, the brain rapidly activates a network of nerve fibers that cause motor movement (withdrawing the hand) immediately.

However, other types of stimuli, such as obtaining visual information when reading an article, activate a much slower reasoning process.

In this way, the brain has an enormous capacity to adapt to the environment. It controls very different but interconnected functions, and modulates the functioning of multiple chemicals.

In fact, it is estimated that more than 50 different molecules are found in the brain that can modify and modulate brain function. Likewise, it is estimated that a human brain has more than 150 billion neurons.

Neuroplasticity

Neuroplasticity is the process by which the brain regulates its activity and adapts to different situations. Thanks to neuroplasticity, the brain has the ability to modify its neural organization to maximize its activity.

The brain is one of the main regions where this capacity is found, which is why it is concluded that its functioning is not static, and is constantly modified.

This paradigm shift in neuroscience, defined by psychiatrist Norman Dodge, reveals the immense capacity of the brain.

Despite the fact that its parts and its functions are well defined, the brain is not an immutable structure, and it responds to the life experience of the individual, so that two identical brains cannot be found in two different people.

Related diseases

The brain is one of the most important organs in the human body. In fact, brain dysfunction causes immediate death, just as it does with the heart.

This is clearly reflected in strokes, which are a very important cause of death and serious brain damage.

When the brain does not stop working but is injured, multiple diseases can develop.

In general, thanks to the neural plasticity of the brain, slight damage to this region of the brain only slows down the transmission of information. This fact tends to translate in most cases with a notable decrease in intelligence and memory.

More serious damage to the brain, such as that caused by neurodegenerative diseases, causes worse results. Alzheimer's, Parkinson's disease or Huntington's disease are pathologies that cause neuronal death in the brain.

These pathologies usually cause symptoms such as memory loss, walking difficulties or mental disorders, and little by little (as brain cells die) they deteriorate all the functions of the body.

On the other hand, mental disorders such as depression, schizophrenia or bipolar disorder, are also explained due to dysregulation of brain function.

There are also infectious diseases that affect the brain through viruses or bacteria. The best known are encephalitis, bovine spongiform encephalopathy, and Lyme disease.

Finally, some brain disorders are congenital. Pathologies such as Tay-Sachs disease, Fragile X syndrome, Down syndrome, or Tourette syndrome, are genetic alterations that seriously affect the brain.

References

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