Brain

Brains . It is an organ of the nervous system rich in neurons with specialized functions, located in the brain of Vertebrate animals and most of the Invertebrates . In the rest, the main node or group of nodes is called.

Summary

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  • 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 brain primordia is located at least in the so-called ” Cambrian explosion “, when molluscs and worms are observed which, in addition to a vague peripheral nervous system distributed in radial symmetry, have a set of neural ganglia that govern various activities of the organism of these primitive animals; in the worms , Peripates , Arthropods and Procordates the beginning of the “cerebration” is observed, that is, the beginning of the organization of a set of guiding nervous ganglia that serve as a coordinating interface between the interior of the animal’s body and its exterior.

The cephalic location has by no means been random: in primitive vermin, arthropods and procordates with a longilinear body and bilateral symmetry (the same that Homo sapiens maintains ) 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 , an initial (embryonic) link between the dermal cells and the nerve cells of the brain can be observed histologically , since the neurons would be, mutation and evolution by means of a great specialization of dermal cells.

By taking an upright posture, animals like primates come to have the central nervous system (and its main part: the brain) no longer in the front of their body but in the upper part (in both cases: their head ). Corticalization is also phylogenetically explainable , that is, the appearance and development of the cerebral cortex from the limbic system and its progressive development in increasingly complex areas of 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 the embryos in the reticular exploration phase . Gastrula . This tube, during embryogenesis , undergoes a series of modifications that give rise to the mature structure. The first of these is the appearance of three expansions, three vesicles : the anterior Brain , the middle Brain and the posterior Brain; its fluid-filled cavity is a precursor to the cerebral ventricles . Later, these three vesicles give rise to five that, in their gain in complexity, undergo a series of folds that make the structure no longer linear.

General characteristics

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

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

The most important biological function of 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 that promote what we call ‘well-being’ emerge, but that the animal simply observes as the least expensive action that allows it to continue living its present.

Brains control behavior by activating muscles , or by 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 :

  • Rhombencephalon
    • Mylencephalon
      • Oblong marrow
    • Metencephalon
      • Ring bulgeor Varolius Bridge
      • Cerebellum
    • Midbrain
      • Tectum
      • Mesencephalic integument
      • Crus cerebri
    • Forebrain
      • Diencephalon
        • Epithalamus
          • Pineal gland
        • Thalamus
        • Hypothalamus
        • Pituitary gland
      • Telencephalon
        • Arquipalio
          • Basal ganglion
            • Caudate nucleus
            • Black substance
            • Fluted body
          • Cerebral tonsil
        • Paleopalio
          • Piriform crust
          • Olfactory bulb
          • Cerebral tonsil
        • Neopalio
          • 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 input occurs through the activity of substances called Neurotransmitters , substances capable of causing the transmission of the nerve 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 in charge of compensating for the deficiency or excess charges in other neurons. The process can be said to be 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 the results and triggering reactions are transmitted by Neurotransmitters , and the scope of said reaction can be immediate (it directly affects other neurons belonging to the same process region), local (it affects another process region other than the initial one) and / or global (affects the entire nervous system).

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

Cell structure

Despite the large number of animal species in which the brain 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 classes of cells: Neurons and glial cells . It should be noted that glial cells have an abundance ten times higher than that of neurons; in addition, its diverse types perform functions of structural, metabolic support, isolation and modulation of growth or development. Neurons connect to each other to form similar (but not identical) neural circuits to synthetic electrical circuits .

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

The defining characteristic 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 nerve impulse is Electrochemistry : through the plasma membrane of the neurons a selective flow of ions takes place that causes the propagation in one direction of a Potential Difference , the presence and frequency of which carries the information. Now, this action potential can be transmitted from one neuron to another by means of aElectrical synapse (i.e. allowing the potential difference to travel as in a conventional circuit) or, much more commonly, by specialized junctions called Synapses.A typical neuron has a few thousand synapses , although some types have a very large number Thus, when a nerve impulse reaches the synaptic button (the end of the axon), the release of specific neurotransmitters that transport the signal to the dendrite of the following neuron occurs , which, in turn, transmits the signal by an action potential and so on.

As for 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 by multiple layers of membrane called Myelin and which is produced by glial cells. Thus, gray substance is spoken of as that rich in neuronal somas and white substance as the part rich in axons (that is, nerve fibers).

Human brain morphology

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

  • The frontal lobeis limited by Silvio’s , Rolando’s, and subfrontal clefts .
  • The parietal lobeis delimited from the front by the Rolando fissure, from below by the Silvio fissure and from behind by the occipital fissure; inside, through the subparietal groove. It extends on the external face of the hemisphere, occupying only a small part of the internal face.
  • The occipital lobeis limited by the external and internal perpendicular fissures, in front; there is no limit on the inside of it. It is located at the back of the brain.
  • The temporal lobeis delimited by Silvio’s fissure and is located in a lateral position.

Even though the two human hemispheres are opposite, they are not the inverted geometric image of each other. From a purely morphological point of view they are asymmetric . 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 human phylogeny , such as the chimpanzee . For this reason, the study of cranial impressions of ancestors of the Homo genus has among its objectives to determine the presence or not of asymmetry in the telencephalon, since it is a feature of increased specialization, of cognitive ability . more complex.

The functional differences between hemispheres are minimal and only in a few areas have differences been found in terms of functioning, there being exceptions in people who did not observe differences. The difference in skills between the two cerebral hemispheres seems to be unique to the human being. It has been said that Language and Logic (the currently best-known areas specialized in language are the Broca and Wernicke’s , although when doing a linguistic process it is likely that the whole brain is involved – almost certainly the areas of memoryparticipate in the language process-, the Broca and Wernicke areas are found in most individuals in the left hemisphere; For their part, the areas most involved in logic and intellectual activities are located mainly in the prefrontal cortex , with the left temporal areas perhaps having great importance for processes of analysis and synthesis, such as those that allow mathematical calculations to be made), these areas provide the individual with greater ability 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 may prioritize homeostatic bodily functions , such as heart beat , blood pressure , fluid balance, and body temperature . However, the one 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 surpasses even the best computers today. Some scientists believe that a brain that performs more Synapses can develop greater Intelligence than one with less neuronal development.

Until not many years ago, it was thought that the brain had exclusive zones of operation until it was determined through imaging that when a function is performed, the brain acts in a similar way to a symphony orchestra interacting several areas 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

In the parietal lobes, the emotional system and the value system develop. The emotional system is although it involves the entire brain – and in feedback, to 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 in the activity that we are doing outside are focused. On the other hand there is the valuation system, this is the relationship that exists between the prefrontal lobes(which as its name implies is behind the forehead) and the brain tonsils, that ” physical ” relationship is called the hippocampus .

Brain and language

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

Wernicke’s area, in charge of decoding the ear and preparing possible responses, then gives way to Broca’s area, where the actuation of the phonary muscles is activated to ensure the production of articulated sounds, which has place in the primary motor area, from where the orders to the phonary muscles depart.

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. The stem cells , the source of these neurons may 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, given the need for damaged regions, glial cells duly stimulated by T cells or thymocytes, could receive the information encoding a change in their structure; coming to transform into a neuron.

Pathology

The brain, along with the heart, is one of the two most important organs of 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 loss of neurochemical transaction, making it difficult to express behavioral traits in need of intelligence , memory and body control. In most cases, these damages are usually due to inflammations, edema , or impacts to the head . The stroke caused by blockage of blood vessels in the brain are also a major cause of death and brain damage.

Other brain problems can be better classified as diseases than as damage. The neurodegenerative diseases such as Alzheimer’s , the Parkinson ‘s disease , the amyotrophic lateral sclerosis and Huntington ‘s disease are caused by the gradual death of individual neurons and currently can only treat your symptoms. The mental illnesses such as clinical depression , the schizophrenia , the disorder bipolar have a theoretical biological basis in the brain and usually treated with psychiatric therapy .

Some infectious diseases that affect the brain are caused by viruses or bacteria . Meninges infection can lead to Meningitis . The Bovine Spongiform Encephalopathy , also known as mad cow , is a fatal disease between cattle and is associated with prions . Furthermore, multiple sclerosis , Parkinson’s disease and Lyme disease , as well as encephalopathy and encephalomyelitis, have been verified to have viral or bacterial causes.

Some disorders of the brain are Congenital . The Tay-Sachs disease , the Fragile X syndrome , the syndrome 22q13 deletion , the Down Syndrome and Tourette syndrome are associated with errors Genetic or chromosome .

Human brain and artificial intelligence

There is a tendency to compare the brain with man’s electronic conduits. It should not be done, as it usually falls into demagoguery and even plot fallacies. There is no scientific basis that can demonstrate without margin of error that the data of the comparisons are 100% reliable, so these studies are estimates by comparison between equivalent concepts. Although the 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 for 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 out of the hands of some private entity, without agreement with a prestigious university that endorses those 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 RCA Corporation’s Advanced Technology Laboratories offers these comparisons, as published in the magazine “ Business Week”So that’s why, with all the existing human technology, the human brain still has a capacity 10 times greater than what is stored in the National Archives of the United States , 500 times greater than an advanced computer memory system and 10,000 times greater than what is recorded in the “ Encyclopedia Britannica .”

Given their great capacity to optimize energy, neurons always interact to avoid a higher cost, so that ‘unused’ regions become less 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 go blank.

In the field of Artificial Intelligence there is a Paradox called the Moravec Paradox . It dictates that, in an anti-intuitive way, human reasoned thinking requires little Computing , while sensory and motor skills, not conscious and shared with many other animals, require great 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 capabilities similar to that of an adult human in intelligence tests, and difficult or impossible to achieve that they possess the perceptual and motor skills of a one-year-old baby ».

The brain in data

  • The cerebral cortexof the human brain contains approximately 15,000 to 33,000 million neurons depending on gender and age.
  • Each of which are interconnected with up to 10,000 synapticconnections . Each cubic millimeter of the 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 this number to 10 billion and others to expand it to 100,000 million.
  • Of all the weight of our body, the brain only represents between 0.8% and 2% (approximately between 1,300-1,600 grams).
  • Consumption of energy(in the form of oxygen and glucose ) of the brain relative to the rest of the body is about 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 the activity ordered by the conscious.
  • If it is about studying while doing sports (for example), the same energy that the brain should be using for that activity, derives it to other functions related to learning, concentration and attention.
  • The more you train to perform multiple activities at the same time, the less energy the 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 quantity that the human being supports, more energy possibly ends up in mental pathologies; Less energy would cause an immediate disconnection of the less representative parts in preserving the homeostaticstate (analogous to what it would mean to plug a short-circuited appliance into its electronics or its electrical components, the brain that increases its consumption to more than 20% has something broken and the one that decreases it, is that it does not get enough, the brain has a nominal consumption depending on the work to be done).
  • Measurements of neuronal density per unit volume, suggest that in a human brain whose capacity ranges from 1,100 to 1,500 cc, they may contain an order of about 100 Billionneurons, each of which interconnects with others by a number of synapses ranging 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 suggests a neural count of about 86,000 million.
  • All sensory experience, conscious or unconscious, is registered in the neural apparatus and can be evoked later, if certain favorable conditions exist; and something similar happens with our unconscious hereditary knowledge that constitutes an even greater potential base (Popper, 1980, p. 136-7).
  • Likewise, the vastness and resources of the mind are so efficient that man can choose, at any given moment, each of the <math> 10,000,000,000 ^ 4 </math> different sentences available to a cultured language (Polanyi , 1969, p. 151).
  • The currently known fossil record (February 2009) of a brain has been found in skulls of fish of the genus Inioptengiusthat lived about 300 million years ago.
  • The human brain can store information that “would fill about twenty million volumes, as in the world’s largest libraries” ( 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).
  • Man’s brain “is endowed with a considerably greater potentiality than can be used during a person’s life” ( Encyclopedia Britannica, 1976, Macropedia, tome 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 machine for the transformation of energy and an example to be followed by students of thermodynamics. We can ask ourselves what meaning or meaning does this amazing capacity of the human brain have, that resides in its optimized way of memorizing and in 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 disposition that will allow the most evolved species to survive on earth for longer.

Neuroplasticity

Neurocity is the process of modifying the neural 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, it gives rise to neuroplasticity. Historically, neuroscience conceived during the 20th centurya static schematic of the oldest brain structures as well as the neocortex. However, it is now known that brain connections vary throughout the adult’s life, as well as the generation of new neurons in areas related to memory management ( Hippocampus , Toothed gyrus ). According to the scientific knowledge of neuroplasticity, mental processes (the fact of thinking, of learning ) are capable of altering the pattern of brain activation in neocortical areas. Thus, the brain is not an immutable structure, but responds to the individual’s life experience. This change in the Paradigmof neuroscience has been defined by Canadian psychiatrist Norman Doidge as “one of the most extraordinary discoveries of the 20th century”

 

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