The Human Brain
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What is the brain? The brain is a complex organ that forms part of our Central Nervous System (CNS) and makes up the biggest part of the encephalon. It is located in the anterior and superior region of the cranial cavity, and it's present in all vertebrae. In the cranium, the brain floats in a transparent liquid, called cerebrospinal fluid, which protects the brain both physically and immunologically.
Is the brain a muscle? We often hear that the brain has to be exercised so that it doesn't atrophy, just like muscles. However, it's important to understand that the brain is not a muscle. The brain is not made up of myocytes, the cells muscles are made of, but rather by millions of neurons that are interconnected by axons and dendrites. They regulate each and every one of our brain's and body's functions. From breathing, or eating or running, to the ability to reason, to fall in love, or to argue, everything passes through our brain's control.
What does our brain do? Functions of the brain
As a fundamental part of the encephalon and the CNS, the brain could be defined as the "manager" of controlling and regulating the majority or brain and body functions. From vital functions like breathing, to other functions like hunger, or thirst, and finally to superior functions like reasoning, attention, and memory, the brain is responsible for making sure all of these conscious and subconscious functions are being carried out.
Everything that happens in our lives, when we're awake or asleep, whether it be breathing, swallowing, seeing, hearing, touching, reading or writing, singing or dancing, thinking silently or talking out loud, loving or hating, walking or running, planning or acting spontaneously, imagining or creating, etc. To put it in a list, some of the functions our brain is responsible for are:
- Controlling vital funcions: Like controlling body temperature, blood pressure, heart rate, breathing, sleeping, eating...
- Receiving, processing, integrating, and interpreting all of the information that we receive through our senses: Sight, hearing, taste, touch, smell.
- Controlling movements and our posture: Walking, running, talking, standing.
- It is responsible for our emotions and behavior.
- It allows us to think, reason, feel, be...
- Controlling superior cognitive functions: Memory, learning, perception, executive functions...
"Men ought to know that from nothing else but the brain come joys, delights, laughter and sports, and sorrows, griefs, despondency, and lamentations. And by this, in an especial manner, we acquire wisdom and knowledge, and see and hear, and know what are foul and what are fair, what are bad and what are good, what are sweet, and what unsavory... And by the same organ we become mad and delirious, and fears and terrors assail us... All these things we endure from the brain, when it is not healthy...I am of the opinion that the brain exercises the greatest power in the man" Hippocrates(s.IV aC) On the Sacred Disease.
Hippocrates knew it then, that the human brain is one of the most complex, enigmatic, and at the same time, perfect creations in the universe. In his time, Hippocrates and his contemporaries couldn't begin to imagine everything that we've since learned about the brain. Thanks to technological advancements in neuroimaging, medicine, biology, psychology, and neuroscience, we have been able to uncover grand mysteries about anatomy and how we function. However, there are still many questions left to be answered.
Parts of the brain
All vertebrates (animals with bones) have a brain which is composed of the following parts:
- The Brainstem: made up of the spinal cord, the pons, and the midbrane. The brainstem controls automatic functions, like blood pressure and heart beat, limbic movements and visceral functions, like digestion or urination.
- Cerebellum: It is the second largest organ in the encehpalon, and it is mainly involved in controlling posture and movement.
- Hypothalamus and pituitary gland, responsible for visceral functions like regulating body temperature and basic behaviors, like eating, sexual response, pleasure, aggression...
- The Brain, made up of the cerebral cortex (hemispheres and cerebral lobes) and some deep structures, like the basal ganglia, amygdala, and the hippocampus. It is in charge of integrating all of the information collected by our sensory organs and organizing a response. It controls motor functions, emotions, and all of the superior cognitive functions: reasoning, emotional expression, memory, learning...
Characteristics of the human brain
How much does the human brain weigh? How big is it? How many neurons are in the brain?
- The cerebral cortex in humans is one of the most evolved and complex among all animal species. It's not only bigger, but it's also rolled and folded back over itself, forming grooves and folds which gives it that characteristic wrinkled appearance.
- The human encephalon weighs about 1.4-1.5 kilos (3.3 lbs), and has a volume of about 1130 cc (69 ci) in women and 1260 cc (77 ci) in men.
- The brain (and the brainstem) are covered by membranes, called meninges, that protect the skull when it is hit.
- For even more protection, the brain "floats" in cerebrospinal fluid.
- It is estimated that the human brain is made up of more than 100 billion nerve cells, mostly glial cells and neurons.
NEURONS: Are the cells that are specialized in receiving, processing, and transmitting information on intercelular and intracelular levels. This is done through electrochemical signals (nerve pulses) called action potential. Structurally, neurons have the same cytoplasmic elements and the same genetic information as the rest of the cells in the organism. Neurons are made up of three parts:
- Cell body or soma: is the main part of the cell that contains the nucleus (with DNA), the endoplasmic reticulum and ribosomes (produce proteins), and mitochondria (generate energy). The soma is where the majority of the cell's metabolic functions take place. If the soma dies, the cell dies.
- Axons: are an extension that comes off of the cellular soma. It is a type of "cable" that has terminal buttons (varicosities) at the end, which are the synaptic contact points, through which nerve pulses are transmitted (pre-synaptic element). The length of the axons can vary from neuron to neuron: there are somevery short ones (less than 1 mm), and others that are very long (more than a yard, which are usually peripheral nerves like motorneurons). Some axons (especially motor and sensory neurons) are covered by a layer of mylein which speeds it up and makes it easier to transmit information. The more myelin an axon has, the stronger it will arrive to the impulse nerve. The neurons that have the most myelin are the periphery neurons (sensory and motor), which is where the information has to travel the furthest.
- Dendrites: are some nerve endings that come off of the cellular soma which branch off into the shape of a tree. Dendrites make up the main component for information reception (post-synaptic element), and they are what make it possible to communicate between two neurons.
GLIAL CELLS: Are the most abundant type of cell in the CNS. They have the ability to divide in the adult brain (neurogenesis), and their presence is necessary for the brain to function properly. These cells make up the structural support for neurons, the cover axons with mylein for a better synaptic transmission (Schwann cells), they play a roll in the cell's nutrition, they participate in regeneration mechanisms and nerve reparation, in the immunization mechanisms, maintaining the blood brain barrier, etc. There are various types of glial cells, among of which are astrocytes, oligodendrocytes, and microglia. In the peripheral nervous system Schwann cells, satellite cells, and macrophages:
- Gray matter in the brain corresponds primarily to the neuron's somas and dendrites.
- White matter is the area where the neuron's axons are predominant. They have more of a whitish coating because most of them carry myelin.
How does the brain work?
The brain works by transmitting information between neurons (or other receptor or effector cells) through electrochemical pulses. This transmission of information is produced during synapsis. During synapsis, neurons and cells connect and through chemical charges and electric pulses and neurotransmitters are exchanged, which are in charge of activating or inhibiting the action of the other cell. The axon's terminal buttons are the pre-synaptic elements of neural communication, through which the neuron establishes communication with the dendrites, the soma, or even another axon.
All of this transmission of information by neurons happens in just milliseconds. Hundreds of connections that allow us to perceive, understand, and react appropriately are coordinated. We receive thousands of inputs, and we generated thousands of outputs in a matter of seconds, and everything works with the precision of a Swiss watch. We can imagine our brain as a big cable that connects our whole body to the brain.
Development of the human brain
How does the human brain develop? The development of the human brain starts in the embryonic stage and ends at youth. After only 4 weeks after conception, the brain starts forming a neural tube where the brainstem comes from. The vertiginous process starts after, where the proliferation, migration, and cell differentiation processes start, where the formation and development of the brain will take place. Neurons are produced in the neural tube and later migrate to form the important parts of the brain. Lastly, they are differentiated and specialized in the function they'll have.
It has been calculated that in the pre-natal stageup to 250,000 brain cells could be produced a minute. In fact, a baby's brain at birth already has all of the nerve cells that it will need, but they are yet to be connected. During the first two years, these connections begin to form mediated by a genetic component, but mainly by interaction with the environment and the stimuli that they received. The mylenization processes (process where the neural fibers are covered with an isolating layer of fat that transfers information) makes it easier to do this faster, and they are responsible for increasing the size of the encephalon.
From 0-12 months: Babies haven't developed the brainstem or spinal cord, which is why they only respond to reflex stimuli and basic survival functions like sleeping, eating, or crying. As they relate to their environment, new connections will be created, and they'll quickly learn things like how to direct their eyes, repeat sounds, understand language...
At 3 years: the brain already is already almost 80% of its adult size, and the limbic system and the cerebral cortex are quite developed. This allows children to express themselves and recognize emotions, play, and start counting and talking. This is why it is considered that at this age, the brain has its maximum brain plasticity, where even if an area is damaged it will regain functions (because it isn't completely specialized yet).
The brain doesn't stop developing until after youth: The area that takes longest to mature are the frontal lobes, which specialize in behavior, reasoning, problem solving, etc.
However, even when brain maturation ends in youth, the brain continues with its neurogenesis processes (creation of new neurons), and they can create new brain connections through training and reinforcement. This is the basis of brain plasticity.
Is it possible to train and improve the brain? How CogniFit helps
Thanks to brain plasticity and to our brain's ability to create new connections and strengthen old ones, we can improve our cognitive capacity. Cognitive stimulation and training through exercises like the ones that CogniFit provides can help you with this.