Brain

Brain . It is an organ of the nervous system rich in neurons with specialized functions, located in the brain of vertebrate animals and most invertebrates . In the rest, the main organ is called the ganglion or set of ganglia.

Summary

[ disguise ]

• 1 Prehistory
• 2 General characteristics
  • 1 Regions
  • 2 Neurotransmission
  • 3 Cell structure
  • 4 Human brain morphology
• 3 Functions
  • 1 Cognitive abilities
  • 2 Brain and language
  • 3 Brain regeneration
• 4 Pathology
• 5 Human brain and artificial intelligence
  • 1 The brain in data
  • 2 Neuroplasticity
• 6 See also
• 7 Source

Prehistory

The existence of cerebral primordia is located at least in the so-called ” Cambrian Explosion “, when mollusks and worms are observed that, in addition to a peripheral and diffuse vague nervous system distributed in a radial symmetry , have a set of neural ganglia that govern various activities of the organism. of these primitive animals; In worms , Peripatos , Arthropods and Prochordates the beginning of “cerebration” is observed, that is, the beginning of the organization of a set of governing nervous ganglia that serve as a coordinating interface between the interior of the animal’s body and the outside of the same.

The cephalic location has by no means been random: in the primitive worms, arthropods and prochordates with a longilinear body and bilateral symmetry (the same as that maintained by Homo sapiens ) the central nervous system is located in the anterior or front part since it is (for example in a worm) the first part to come into intense contact with the environment, in the same way histologically an initial link (embryonic) can be observed between the dermal cells and the nervous cells of the brain since the neurons would be, mutation and evolution through a great specialization of dermal cells.

By taking an upright posture, animals such as primates begin to have the central nervous system (and its main part: the brain) no longer in the front part of their body but in the upper part (in both cases: their head ). Corticalization is also phylogenetically explainable , this is the appearance and development of the cerebral cortex from the limbic system and its progressive development into areas of increasingly complex neuronal architecture.

This phylogenetic development can be perceived ontogenetically in each chordate animal embryo by observing the so-called ” Häckel Recapitulation “. The precursor structure of the nervous system is the Neural Tube , a structure that appears on the outside of embryos in the Gastrula reticular exploration phase . This tube, throughout embryogenesis , undergoes a series of modifications that give rise to the mature structure. The first of them is the appearance of three expansions, three vesicles : the anterior brain , the middle brain and the posterior brain ; Its cavity, filled with fluid, is the precursor of the cerebral ventricles . Later, these three vesicles give rise to five that, as they gain complexity, undergo a series of foldings that make the structure no longer linear.

General characteristics

In vertebrates the brain is located in the Head , protected by the Skull and close to the primary sensory apparatuses of Vision , Hearing , balance , Taste, and Smell .

Brains are extremely complex. The complexity of this Organ emerges from the nature of the unit that nourishes its functioning: the Neuron . These communicate with each other through long protoplasmic fibers called axons , which transmit trains of pulses of signals called action potentials to distant parts of the brain or body, depositing them in specific receptor cells.

The most important biological function performed by the brain is to manage the energy resources available to the animal to promote behaviors based on the economy of its survival. Based on this, behaviors emerge that promote what we call ‘well-being’, but which the animal simply observes as the least costly action that allows it to continue living its present.

Brains control behavior by activating muscles , or producing the secretion of chemicals such as hormones . Even single-celled organisms may be able to obtain information from their environment and act in response to it.

Regions

The following regions are identified in the brain of chordates :

• Hindbrain
  • Myelencephalon
    • medulla oblongata
  • Metencephalon
    • Annular protuberance or Pons of Varolio
    • Cerebellum
  • Midbrain
    • tectum
    • mesencephalic integument
    • Crus cerebri
  • Prosencephalon
    • diencephalon
      • Epithalamus
        • Pineal gland
      • Thalamus
      • hypothalamus
      • Pituitary gland
    • Telencephalon
      • Arquipalio
        • basal ganglia
          • caudate nucleus
          • Black substance
          • striatum
        • Brain amygdala
      • Paleopalium
        • piriform cortex
        • Olfactory bulb
        • Brain amygdala
      • Neopallium
        • Cerebral cortex
          • frontal lobe
          • Temporal lobe
          • parietal lobe
          • Occipital lobe
          • Brodmann areas
          • Insula
          • cingulate cortex

Neurotransmission

The transmission of information within the brain as well as its afferents occurs through the activity of substances called Neurotransmitters , substances capable of causing the transmission of the nervous impulse . These neurotransmitters are received in the Dendrites and emitted in the axons . The brain uses biochemical energy from cellular metabolism as a trigger for neuronal reactions .

Each neuron belongs to a metabolic region responsible for compensating for the deficiency or excess of loads in other neurons. It can be said that the process is complete when the affected region is no longer active. When the activation of one region results in the activation of a different one, it can be said that there has been a biomolecular exchange between both regions. All results and triggering reactions are transmitted by Neurotransmitters , and the scope of said reaction can be immediate (directly affects other neurons belonging to the same process region), local (affects another process region other than the initial one) and/or or global (affects the entire nervous system).

A neurotransmitter is a molecule in a transition state, with a deficit or surplus of charges. This transition state gives a maximum stability time of a few molecular vibrations. During this time, the molecule must attach to the appropriate postsynaptic receptor, otherwise it degrades and remains as waste in the cerebrospinal fluid. Astrocytes are responsible for cleaning this fluid of these wastes, allowing future neurotransmissions not to be interfered with .

Cell structure

Despite the large number of animal species in which brains can be found, there are a large number of common characteristics in their cellular, structural and functional configuration. At the cellular level, the brain is made up of two kinds of cells: Neurons and glial cells . It should be noted that glial cells have an abundance ten times greater than that of neurons; Furthermore, its diverse types perform functions of structural support, metabolism, isolation and modulation of growth or development. Neurons connect with each other to form neural circuits similar (but not identical) to synthetic electrical circuits .

The brain is divided into sections separated spatially, compositionally, and in many cases, functionally. In mammals, these parts are the Telencephalon , the Diencephalon , the Cerebellum , and the Brainstem . These sections can be further divided into hemispheres , lobes , cortex , areas, etc.

The characteristic that defines the potential of neurons is that, unlike glia, they are capable of sending signals over long distances. This transmission is carried out through its Axon , a long and thin type of Neurite ; The signal is received by another neuron through any of its Dendrites . The physical basis of the transmission of the nervous impulse is Electrochemistry : through the plasma membrane of the neurons, a selective flow of ions is produced that causes the propagation in only one direction of a Potential Difference , whose presence and frequency carries the information. Now, this action potential can be transmitted from one neuron to another through an electrical Synapse (that is, allowing the potential difference to travel as in a conventional circuit) or, much more commonly, through specialized junctions called Synapses. A typical neuron has a few thousand synapses , although some types have a much smaller number. In this way, when a nerve impulse reaches the synaptic button (the end of the axon), the release of specific neurotransmitters occurs that transport the signal to the dendrite of the next neuron, which, in turn, transmits the signal through an action potential and so on.

In terms of brain mass, axons are its majority component. In some cases the axons of groups of neurons follow joint tracts. In others, each axon is covered with multiple layers of membrane called Myelin , which is produced by glial cells. In this way, we speak of gray matter as that rich in neuronal somata and white matter as the part rich in axons (that is, nerve fibers).

Human brain morphology

The telencephalon is the largest part of the human brain . It covers the dorsal part of the Cerebellum , being separated from it by its tentorium. It is divided by the interhemispheric fissure into two hemispheres joined together by the interhemispheric commissures and have the lateral ventricles inside as the ependymal cavity . Each hemisphere has several fissures that subdivide it into lobes:

• The frontal lobe is limited by the Sylvian and Rolandic fissures and the subfrontal fissure .
• The parietal lobe is delimited in front by the Rolando fissure, below by the Sylvian fissure, and behind by the occipital fissure; inside, through the subparietal sulcus. It extends on the outer face of the hemisphere, occupying only a small part of the inner face.
• The occipital lobe is limited by the external and internal perpendicular fissures, in front; There is no limit on the inside of it. It is located in the back of the brain.
• The temporal lobe is delimited by the Sylvian fissure and is located in a lateral position.

Even though both human hemispheres are opposite, they are not the inverted geometric image of each other. From a purely morphological point of view they are asymmetrical . This asymmetry depends on a pattern of gene expression that is also asymmetric during the embryonic development of the individual, and is not present in close relatives in the phylogeny of humans, such as the chimpanzee . For this reason, the study of cranial impressions of ancestors of the genus Homo has among its objectives to determine the presence or absence of asymmetry in the telencephalon, since it is a trait of increased specialization, of a more complex cognitive capacity.

The functional differences between hemispheres are minimal and only in a few areas have differences in functioning been found, with exceptions existing in people for whom no differences were observed. The difference in skills between the two cerebral hemispheres seems to be exclusive to humans. It has been said that Language and Logic (the currently best-known areas specialized in language are Broca’s and Wernicke ‘s , although when carrying out a linguistic process it is likely that the entire brain is involved – almost undoubtedly the memory areas participate in the language process, Broca’s and Wernicke’s areas are found in most individuals in the left hemisphere; meanwhile, the areas most involved in logic and intellectual activities are located mainly in the prefrontal cortex , perhaps having the left temporal areas are of great importance for analysis and synthesis processes such as those that allow mathematical calculations) these areas provide the individual with a greater capacity to adapt to the environment, but with much longer learning processes, and as such more dependent on their parents. during the breeding stage.

Features

The brain processes sensory information, controls and coordinates Movement , Behavior and can prioritize homeostatic bodily functions , such as heartbeat , Blood Pressure , fluid balance and Body Temperature . However, the person in charge of carrying out the automatic process is the Medulla oblongata . The brain is responsible for Cognition , emotions , memory and Learning .

The processing and storage capacity of a standard human brain exceeds even the best computers today. Some scientists believe that a brain that makes a greater number of Synapses can develop greater Intelligence than one with less neuronal development.

Until not many years ago, it was thought that the brain had exclusive areas of operation until, through Imaging, it was determined that when a function is performed, the brain acts in a manner similar to a symphony orchestra, several areas interacting with each other. Furthermore, it was established that when a non-specialized brain area is damaged, another area can perform a partial replacement of its functions.

Cognitive abilities

The emotional system and the evaluative system develop in the parietal lobes. The emotional system is, although it involves the entire brain – and in feedback, the entire body of the individual – it is located mainly in the rather archaic area called the Limbic System , within the limbic system the 2 cerebral tonsils (each located behind the eye, at a depth of approximately 5 cm), the basic emotions (fear, aggression, pleasure) that we have and that we give when something or someone interferes with the activity we are doing outside are focused. On the other hand, there is the evaluative system, this is the relationship that exists between the prefrontal lobes (which, as its name indicates, is behind the forehead) and the cerebral amygdalae, that ” physical ” relationship is called the hippocampus .

Brain and language

Sound perception of speech occurs in Heschl’s gyrus, in the right and left hemispheres. This information is transferred to Wernicke’s area and the inferior parietal lobe, which recognize the phonemic segmentation of what is heard and, together with the prefrontal cortex, interpret those sounds. To identify the meaning, they contrast that information with that contained in various areas of the temporal lobe.

Wernicke’s area, responsible for decoding what is heard and preparing possible responses, then gives way to Broca’s area, in which the activation of the speaking muscles is activated to ensure the production of articulated sounds, which has place in the primary motor area, from where the orders to the speaking muscles originate.

Brain regeneration

The adult human brain, under normal conditions, can generate new neurons. These new cells are produced in the hippocampus, a region related to memory and learning. Stem cells , the origin of these neurons, can thus constitute a potential reserve for neuronal regeneration of a damaged nervous system.

Recent studies point to new lines of research, which are based on the observation of brains that have suffered trauma and in which neurons have been found where there should have been scar tissue . This suggests that, if damaged regions are needed, glial cells duly stimulated by T cells or thymocytes could receive information that encodes a change in their structure; becoming a neuron.

Pathology

The brain, along with the heart, is one of the two most important organs in the human body. A loss of functionality of either of these two organs leads to Death . On the other hand, damage to the brain causes losses of neurochemical transaction, making it difficult to express behavioral traits that require intelligence , memory, and body control. In most cases, these damages are usually due to inflammation, edema , or impacts to the head . Strokes caused by blocked blood vessels in the brain are also a major cause of death and brain damage.

Other brain problems may be better classified as diseases than damage. Neurodegenerative diseases such as Alzheimer’s Disease , Parkinson’s Disease , Amyotrophic Lateral Sclerosis and Huntington’s Disease are caused by the gradual death of individual neurons and currently only their symptoms can be treated. Mental illnesses such as Clinical Depression , Schizophrenia , Bipolar Disorder have a theoretical biological basis in the brain and are usually treated with psychiatric therapy .

Some infectious diseases that affect the brain are caused by Viruses or Bacteria . Infection of the Meninges can lead to Meningitis . Bovine spongiform encephalopathy , also known as mad cow disease , is a fatal disease among cattle and is associated with prions . Likewise, it has been verified that Multiple Sclerosis , Parkinson’s Disease and Lyme Disease , as well as encephalopathy and encephalomyelitis, have viral or bacterial causes.

Some brain disorders are congenital . Tay-Sachs Disease , Fragile X Syndrome , 22q13 deletion syndrome , Down Syndrome and Tourette Syndrome are associated with Genetic or chromosomal errors .

Human brain and artificial intelligence

There is a tendency to compare the brain with the electronic conduits of man. It should not be done, as it tends to fall into demagoguery and even argumentative fallacies. There is no scientific basis that can demonstrate without margin of error that the comparison data are 100% reliable, so these studies are estimates by comparison between equivalent concepts. Although equivalences may satisfy the requirements of certain scientists, they themselves recognize their limits when it comes to understanding the exact functioning of the brain.

In the past, the euphoria of engineers over technological achievements led them to compare brain processes with electronic ones, establishing equivalences. However, the economic interests of companies use these studies for their commercial purposes. Thus, these studies always come from the hand of some private entity, without agreement with a prestigious university that endorses these results. We have the case of the typical comparison that exists between computer memories , as well as other methods of retaining information, and the memory capacity of the human brain. The company Advanced Technology Laboratories of the RCA Corporation offers these comparisons, as published in the magazine “ Business Week ”: Therefore, with all the existing human technology, the human brain still has a capacity 10 times greater than what is stored in the United States National Archives , 500 times larger than an advanced computer memory system and 10,000 times larger than what is recorded in the “ Encyclopedia Britannica .”

Given their great capacity to optimize energy, neurons always interact to avoid a higher cost, so ‘unused’ regions become poorly optimized regions. An unused neuron is more expensive to maintain than when it is connected to a synaptic network. Therefore, when a neuron is isolated from the rest, its tendency is to die, and not to remain blank.

In the field of Artificial Intelligence there is a Paradox called Moravec’s Paradox . This dictates that, counterintuitively, human reasoned thinking requires little computing , while sensory and motor skills, non-conscious and shared with many other animals, require large computational efforts. This principle was postulated by Hans Moravec and others in the 1980s. As Moravec said: “It is comparatively easy to get computers to show abilities similar to those of an adult human in intelligence tests, and difficult or impossible to get them to possess the perceptual and motor skills of a one-year-old baby.

The brain in data

• The cerebral cortex of the human brain contains approximately 15,000 to 33,000 million neurons depending on gender and age.
• Each of which is interconnected with up to 10,000 synaptic connections . Each cubic millimeter of cerebral cortex contains approximately 1 billion synapses.
• Its surface (the so-called cerebral cortex ), if extended, would cover an area of ​​1,800-2,300 square centimeters.
• It is estimated that inside the cerebral cortex there are about 22,000 million neurons, although there are studies that reduce that figure to 10,000 million and others extend it to 100,000 million.
• Of the entire weight of our body, the brain only represents between 0.8% and 2% (approximately between 1,300-1,600 grams).
• Energy consumption (in the form of Oxygen and Glucose ) of the brain in relation to the rest of the body is approximately 20%, remaining very stable around that value regardless of body activity.
• For this reason there are activities that are incompatible with each other, since the brain varies the amount of energy consumed with reference to the circulatory system, and consequently to that of the rest of the body. For example, if you play sports and burn 1,500 Calories , the brain will have consumed 20%, of which it has invested in activating the brain region that controls the body part that in turn executes the orders in the physical parts that have interacted with it. the activity ordered by the conscious.
• If it is about studying while playing sports (for example), the same energy that the brain should be using for that activity, it diverts to other functions related to learning, concentration and attention.
• The more you train yourself to perform several activities at the same time, the less energy your brain will use to perform those same functions in the future, since it will not need to create the necessary synaptic links that allow this type of “multitasking.”
• Different brain regions coming into play with parallel consumption will reduce the quality of activities.
• The brain cannot and should not consume more than 20% of the body’s overall energy. It is the amount that the human being supports, the more energy possibly leads to mental pathologies; less energy would cause an immediate disconnection of the parts that are less representative when it comes to maintaining the homeostatic state (analogously to what it would mean to plug in a short-circuited appliance in its electronics or electrical components, the brain that increases its consumption to more than 20% has something broken and what reduces it is that it does not receive sufficient input, the brain has a nominal consumption depending on the work to be done).
• Measurements of neuronal density per unit volume suggest that a human brain, whose capacity ranges between 1,100 and 1,500 cc, may contain an order of about 100 billion neurons, each of which interconnects with others by a number of synapses that ranges from several hundred to more than 20,000, forming a structural network that is about 100 times more complex than the global telephone network. On the other hand, lower densities have been recorded, which suggest a neuronal count of about 86 billion.
• Every sensory experience, conscious or unconscious, is registered in the neuronal apparatus and can be evoked later, if certain favorable conditions are met; and something similar happens with our unconscious hereditary knowledge, which constitutes a base of even much greater potentiality (Popper, 1980, p. 136-7).
• Likewise, the vastness and resources of the mind are so efficient that man can choose, in a given instant, each of the <math>10,000,000,000^4</math> different sentences available to an educated language (Polanyi , 1969, p.
• The currently known fossil record (February 2009) of a brain has been found in the skulls of fish of the genus Inioptengius that lived about 300 million years ago.
• The human brain can store information that “would fill some twenty million volumes, as in the largest libraries in the world” ( Cosmos , by Carl Sagan , 1980, p. 278).
• “The brain of the human infant, unlike that of any other animal, triples in size during its first year” (The universe Within, by Morton Hunt, 1982, p.44).
• The human brain “is endowed with a potentiality considerably greater than that which can be used during a person’s lifetime” ( Encyclopedia Britannica , 1976, Macropedia, volume 12, p. 998).

These and other similar data lead us to conclude that the human brain is the most efficient reality in terms of energy consumption and transformation, as far as we have been able to find in this universe. It is a true energy transformation machine and an example to follow for thermodynamics students. We can ask ourselves what meaning or meaning this has, or what function it plays, this amazing capacity of the human brain that resides in its optimized way of memorizing and its constant increase in the speed of processing information. Our answer is that this gigantic endowment is there, waiting to be taught what is the synaptic arrangement that will allow the most evolved species to survive longer on earth.

Neuroplasticity

Neurocity is the process of modification of the neuronal organization of the brain as a result of experience. The concept is based on the ability to modify the activity of neurons, and as such was described by the Polish neuroscientist Jerzy Konorski . The ability to modify the number of Synapses , neuron-neuron connections, or even the number of cells, gives rise to neuroplasticity. Historically, neuroscience during the 20th century conceived a static scheme of the oldest structures of the brain as well as the neocortex. However, today it is known that brain connections vary throughout the adult’s life, and the generation of new neurons is also possible in areas related to memory management ( hippocampus , dentate gyrus ). According to scientific knowledge of neuroplasticity, mental processes (the act of thinking, learning ) are capable of altering the pattern of brain activation in neocortical areas. Thus, the brain is not an immutable structure, but rather responds to the individual’s life experience. This change in the paradigm of neuroscience has been defined by the Canadian psychiatrist Norman Doidge as “one of the most extraordinary discoveries of the 20th century.”