The human brain is one of the most complex and mysterious structures in nature. It is the center at which we think, feel, remember, learn, create, and act, and it is the root of our identity and personality. However, despite the fact that humans have studied the brain for thousands of years, we still have many unknowns and questions about how it works and functions. Brain science, also known as neuroscience, is an interdisciplinary science dedicated to unraveling the mysteries and potential of the brain. It involves many fields such as biology, chemistry, physics, mathematics, psychology, philosophy, medicine, engineering, etc., using a variety of experimental methods and techniques, from the molecular to the system level, to explore the structure, function, development, evolution, disease, and ** of the brain.
The structure of the brain
The weight of the human brain is about 14 kilograms, which is about 2% of the body weight, but consumes about 20% of oxygen and blood. The brain is made up of two hemispheres, each of which is divided into four lobes: frontal, parietal, temporal, and occipital. These lobes are responsible for different cognitive functions like attention, language, vision, hearing, movement, sensation, etc. The surface of the brain is made up of gray neurons that form a folded cortex, also known as gray matter. The thickness of the cortex is about 2-4 mm, and if unfolded, the area is about 02 square meters. Underneath the cortex are internal structures made up of white nerve fibers, also known as white matter. White matter connects neurons in different regions, allowing them to relay information to each other. At the base of the brain is the brainstem made up of a number of smaller structures that connect the brain to the spinal cord and control some basic physiological functions such as breathing, heartbeat, sleep, and wakefulness. In the brain is the limbic system made up of nuclei that are involved in functions such as emotion, motivation, memory, and reward. Between the two hemispheres of the brain is the corpus callosum made up of bundles of fibers, which is the largest white matter structure of the brain and is responsible for coordinating the activities of both hemispheres.
Functions of the brain
The function of the human brain is made up of a complex neural network of billions of neurons and trillions of synapses. Neurons are the basic units of the brain, and they are capable of generating and transmitting electrical signals. Synapses are junctions between neurons that are able to regulate the intensity and direction of signals through chemicals or electrical currents. The combination and arrangement of neurons and synapses determine the function and plasticity of the brain. The function of the brain can be divided into two levels: local and whole. Local function refers to the response of a particular brain region or group of brain cells to a specific stimulus or task, such as the visual cortex's response to light, or the motor cortex's control of finger movement. Holistic function refers to the cooperation and integration between different brain regions or brain networks, such as attention, memory, emotion, language, consciousness, and other higher-level cognitive functions. The functions of the brain are dynamic, and they change with time, environment, experience, and learning. The brain is malleable, that is, it is able to change its structure and functions as needed to adapt to new challenges and opportunities. The plasticity of the brain is fundamental to human learning and adaptation, as well as the possibility of brain repair and recovery.
The development of the brain
The development of the human brain is a long and complex process that begins in the embryonic stage and continues into adulthood and even old age. The development of the brain is influenced by both genetics and the environment, which together determine the shape, size, connections, and function of the brain. The development of the brain can be divided into several stages: neurogenesis, nerve migration, nerve differentiation, synapse formation, synaptic pruning, and myelination. Neurogenesis refers to the production of neurons, which occurs in the first trimester of the embryonic stage, with about 250,000 neurons born every minute. Neuromigration refers to the movement of neurons, which occurs between the second and sixth months of the embryonic stage, where neurons migrate from where they were produced to their destinations, forming various areas of the brain. Neural differentiation refers to the specialization of neurons, which occurs from the fourth month of the embryonic stage to the months after birth, and neurons develop different shapes, sizes, types, and connections depending on their location and function. Synapse formation refers to the establishment of synapses, which occur between the fifth month of the embryonic stage and a few years after birth, when trillions of synapses begin to form between neurons, allowing them to communicate with each other. Synaptic pruning refers to the elimination of synapses, which occurs in the years after birth to adolescence, where the brain optimizes and stabilizes its own structure and function by eliminating some redundant or ineffective synapses. Myelination refers to the encapsulation of the myelin sheath, which occurs from a few months after birth to adulthood, myelin is a lipid substance that is able to encapsulate nerve fibers and increase the speed and efficiency of signaling.
The evolution of the brain
The evolution of the human brain is a long and amazing process that began with the primitive nervous system hundreds of millions of years ago and has evolved into today's complex and advanced brains. The evolution of the human brain is driven by both natural and cultural selection, which together determine the brain's adaptability and creativity. The evolution of the human brain can be divided into several stages: the primitive nervous system
The primitive nervous system refers to the collection of neurons and ganglia that first appeared in animals, and they are able to respond to external stimuli simply, such as contracting, stretching, avoiding, etc. The primitive nervous system appeared in spongy animals, about 700 million years ago, and they were the simplest multicellular animals, with no real neurons, only a few sensitive cells. With the evolution of animals, the primitive nervous system has gradually developed more complex structures and functions, such as nerve cords, neural networks, neural tubes, etc., which are able to control more movement and sensation.
The neural tube refers to the hollow neural structure that first appeared in chordates, which is located on the back of the embryo and is the precursor of the brain and spinal cord later. The neural tube appeared in jawless fishes about 500 million years ago, and they were the first vertebrates with a cartilage scaffold and a simple brain. As vertebrates evolved, neural tubes gradually differentiated into more complex structures and functions, such as forebrain, midbrain, and hindbrain, which were able to process more information and behavior.
The forebrain refers to the anterior part of the neural tube, which is a precursor to the later cerebral cortex and limbic system. The forebrain appeared in jawed fishes about 400 million years ago, and they were the first jawed vertebrates with a bony skeleton and a larger brain. With the evolution of jawed fishes, the forebrain has also gradually expanded and complexed, forming different regions and functions, such as the olfactory bulb, optic bed, cerebral hemispheres, etc., which are able to process more sensations and cognition.
The cerebral hemispheres refer to the two symmetrical parts of the forebrain, which are the main components of the later cerebral cortex. The cerebral hemispheres appeared in reptiles about 200 million years ago, and they were the first terrestrial vertebrates with a dry ** and a well-developed brain. With the evolution of reptiles, the cerebral hemispheres have gradually increased the number and area of the cortex, forming different lobes and functions, such as frontal, parietal, temporal, occipital, etc., which are able to support more movement and thinking.
The human brain refers to the most complex and advanced brain currently known, which is characteristic and dominant in humans. The human brain appeared in the genus Homo about 2 million years ago, and they were the earliest human ancestors, with an upright posture and a larger brain. With the evolution of human beings, the human brain has also gradually increased the ratio and connections of gray matter and white matter, forming different networks and functions, such as language, memory, emotion, consciousness, etc., which are able to achieve more creativity and culture.