The human brain: structure, functions and ways to keep it healthy
Miscellaneous / / April 02, 2023
Brain weighs about 1.2-1.3 kilograms and controls all body functions - from breathing and heartbeat to emotions and remembering information. This body consists of from different cell types. It has 86 billion neurons that communicate with each other using chemical and electrical signals. As well as about 85 billion glial cells. They provide an optimal environment in which neurons can grow and interact.
Nerve cells form different brain structures, each of which performs its own functions. However, they all work closely together. For example, to shake an outstretched hand, the brain activates several areas responsible for vision and movement at once. And perhaps emotions - if the hand belongs to a person that you do not like or, conversely, causes delight.
Neurons come in different shapes and sizes, but they all have the same structure. Cells are made up of a body, dendrites, and an axon and transmit information through electrical and chemical signals.
Dendrites are extensions of neurons. They work like antennas, receiving messages from other nerve cells.
When the signal enters the body of the neuron, it is transmitted further - to the axon process. That, in turn, releases neurotransmitter chemicals (neurotransmitters) into a small gap between neurons called the synaptic space.
Molecules of neurotransmitters cross the point of contact between two neurons (synapse) and are integrated into the receptors of the dendrite of the receiving nerve cell. And the reaction starts all over again.
in the brain There is There are many types of mediators, and each of them performs its function. For example, the main excitatory substance is glutamate: about 40% of all neurons communicate with it. If the brain does not need some kind of reaction, nerve cells secrete another mediator - gamma-aminobutyric acid (GABA). It inhibits the excitation of neurons and stops the transmission of signals.
There are also many other mediators, such as dopamine, which gives pleasure from the expectation of something pleasant. Or norepinephrine, necessary for concentration and activity during dangerous situations.
telencephalon
The largest part of the brain. It consists of two hemispheres, which are connected from below by the corpus callosum. The surface of the telencephalon - the cerebral cortex - is covered with folds (gyrus) and depressions (furrows). In the process of evolution, this structure allowed the cranium to accommodate a larger volume of cells, while not particularly increasing in size.
Each of the hemispheres controls the opposite part of the body and provides certain qualities and skills. For most people, the left hemisphere is responsible for oral and written speech, language understanding, counting, and the right hemisphere is responsible for creativity, spatial orientation, artistry, and musical skills.
Convolutions and furrows divide the cortex into lobes: frontal, temporal, parietal and occipital. Each of them consists of areas responsible for certain functions.
frontal lobe
- Personality, behavior, emotions.
- Judgment, planning, problem solving.
- Oral speech and writing.
- Body movements.
- Intelligence, concentration, awareness.
parietal lobe
- Speech interpretation.
- Sensation of touch, pain, temperature.
- Interpretation of signals from the organs of vision, hearing, motor and sensory information, memory.
- Spatial and visual perception.
Occipital lobe
- Processing of visual information.
temporal lobe
- Language comprehension (Wernicke's area).
- Memory.
- Hearing.
- Sequence and organization of actions.
Shells of the brain
These are three membranes: hard, arachnoid and soft. They envelop the brain, providing a transition from the bones of the skull to the soft nervous tissue, providing a supportive scaffold for the blood vessels, and protecting the nervous tissue from shock and vibration.
The dura mater is composed of tough connective tissue that resembles a thin sheet of flexible material. It covers the brain, and in some places its processes are embedded inside.
Under the hard shell lies the arachnoid, and under it - the soft one. The latter almost grows together with the surface of the brain, goes into all its cracks and furrows. Between these two membranes there is a space filled with cerebrospinal fluid. It creates a shock-absorbing layer to protect the nervous tissue from impacts, and also maintains a constant intracranial pressure and is involved in metabolic processes between the blood and the brain.
brain stem
This area acts as a relay center, connecting the cerebral cortex and cerebellum to the spinal cord. It provides many automatic functions such as breathing, heart muscle contraction, maintenance of body temperature, sleep and wake cycles, digestion, coughing and sneezing, nausea and swallowing.
The trunk contains three structures:
- Medulla. Controls breathing, blood pressure, heart rate and swallowing.
- Bridge. Involved in eye coordination, facial muscle movement and sensation, hearing and balance. In this structure is a blue spot - a cluster of neurons responsible for attention and response to anxiety and stress.
- Midbrain. Responsible for the control of body movements, vision and hearing, is involved in the regulation of sleep and wakefulness cycles.
Cerebellum
The cerebellum is responsible for coordinating movements. This structure transmits information from the spinal cord to the cerebral cortex and vice versa: shows "center" what is happening with the body at the moment, and then sends commands to the periphery about what is needed do.
The cerebellum helps to perform automatic movements like maintaining a posture. Thanks to him, you, without hesitation, maintain balance, keep your back straight and strain the right muscles.
Also, this structure is involved in the formation of muscle memory and planning of intentional movements, including complex and high-precision ones. For example, it sets up fine motor skills, which are necessary for writing or playing musical instruments.
If you're good at playing computer games with fast, precise joystick control, thank your cerebellum for that.
entorhinal cortex
This structure connects the cerebral cortex and the hippocampus.
The entorhinal cortex transmits various sensations, including sounds, smells and visual images, and the hippocampus collects this data into a big picture and stores it as a memory.
In the future, referring to one part of the impression can help to recreate the whole picture. For example, the smell of perfume can bring to mind the visual image of a person or the sound of his voice.
The entorhinal cortex and the hippocampus are involved in the formation of any memory, including life events, facts, words, and concepts. Also, these structures help to navigate in space and remember what and where is and how to get there.
Olfactory bulb
This is a paired formation in the forebrain responsible for the perception of odors.
Receptors in the nose pick up chemicals in the air and relay the information to the glomeruli of the olfactory bulb, a plexus of "tails," or axons, of nerve cells.
From this structure, data on the chemical composition of the air enters different parts of the brain for analysis and comparison with what is already stored in memory. After that, a person recognizes the presence of chemicals as a certain smell.
limbic system
It is the center of our emotions, learning and memory. This system includes the hippocampus, amygdala (tonsil), hypothalamus, cingulate cortex, fornix, and mammillary bodies.
hippocampus
Responsible for creating long-term memories. Nerve cells in the hippocampus connect with other areas of the brain to form different aspects of memory. For example, episodic - memories of life events and personal facts such as the first kiss or the funeral of a relative, semantic - general knowledge about the world, events and objects, spatial - remembering places and directions.
Amygdala
Paired with the hippocampus, it creates long-term memories of specific and emotional events associated with people or places. The amygdala is associated with fear, aggression and anxiety.
Hypothalamus
Connects the nervous system with the endocrine system. It controls hunger and thirst, the body's response to environmental temperature, sleep and wake cycles, and sexual behavior. In addition, the hypothalamus is involved in the formation of memory and, along with other structures of the limbic system, is associated with the manifestation of emotions.
Belt bark
A group of interacting brain structures responsible for emotions. The anterior cingulate cortex is also involved in the processing of emotional stress from pain.
vault of the brain
bundles white matter that curves around the thalamus and connects the medial temporal lobe to the hypothalamus. The dome of the brain is part of the limbic system and plays a role in the formation of declarative, or explicit, memory - the one that you call consciously, as opposed to the implicit one, which "turns on" without conscious participation.
For example, if you remember how a driving instructor told you to drive through intersections, this is an explicit memory, and if your foot is pressing the brake itself at that moment, it is an implicit one.
Mastoid bodies
Two nucleilocated at the base of the hypothalamus. Participate in the consolidation and storage of the experience of spatial and episodic memory. The first contains information about places and directions, such as how to get to the store, and the second accumulates data on life events and personal facts - the case when in this store you got rude. Also, this part of the brain is involved in the emergence of emotions and regulates behavior aimed at achieving goals and receiving rewards.
optic chiasm (chiasm)
Plot partial crossing of the fibers of the optic nerves, located under the hypothalamus. Due to incomplete crossover, the image from the inner half of the retina enters the opposite part of the brain. And what fell on the outer part of the eye - in the same hemisphere.
As a result, the left hemisphere processes information from the right visual fields in both eyes, while the right hemisphere processes information from those on the left. In the occipital region of the cortex, all the information received is combined, and we see a deep three-dimensional picture.
Basal nuclei
This group of brain structures controls intentional body movements, habitual automatic actions and emotions.
The basal nuclei connect higher nervous activity with sensations and reflexes. They are involved in many processes, including decision making and motivation. For example, the nucleus accumbens and caudate nucleus help reinforce beneficial behavior through the release of dopamine, but may also be involved in the formation of addiction.
Other sites, such as the shell, the globus pallidus, or the substantia nigra, help initiate and suppress unnecessary physical activity so that a person can move smoothly and accurately.
Through the interaction of the basal ganglia with the cerebellum, you can master and memorize complex sequences of movements, for example, play a guitar solo or learn a dance with difficult choreography.
thalamus
Serves as a transmitter of information from most of the senses to other brain structures. Everything that you see, hear, taste, feel inside and outside the body, before reaching the cerebral cortex, passes through the thalamus.
The structure receives a command from the cortex, which is now important to pay attention to, and filters all sensory information. As a result, only what matters at the moment is sent for processing.
Thanks to this "secretary", the brain saves energy, and a person can focus on the task without being distracted by irrelevant sensory information. In addition, the thalamus is connected to other regions of the brain, such as the hippocampus and brain stem, and is involved in maintaining vigilance, memory processes, and retention of attention.
Ventricles of the brain
Fluid-filled cavities that produce cerebrospinal fluid, or cerebrospinal fluid. It flows in and around the brain, nourishing, cleansing and protecting it.
In the hemispheres there are two lateral ventricles, which communicate with the third through the foramen of Monro. He, in turn, is connected to the fourth through a long narrow tube - the Sylvius aqueduct.
From the fourth ventricle, the CSF is directed into the space between the shells and acts as a shock absorber, protecting the brain from injury.
Pituitary
This pea-sized structure, located at the base of the brain, controls most of the body's endocrine glands, including the thyroid, adrenal cortex, testicles, and ovaries.
The anterior lobe of the pituitary gland makes up 80% of the volume of the gland. It produces hormones that start the process of muscle and bone growth, stimulate the testicles to produce sperm, and the ovaries to produce eggs.
Also, the anterior pituitary gland determines the response to stress by causing the adrenal glands to release cortisol, with the help of prolactin stimulates the production of milk in women, and due to endorphins suppresses the feeling of pain and controls immunity.
The posterior pituitary gland produces only two hormones - vasopressin and oxytocin. The first maintains the water balance of the body, the second performs several functions, including contraction of the uterus during childbirth and the formation of a warm emotional bond between people.
corpus callosum
A thin wide bundle of axons that transmits signals between different structures of the left and right hemispheres and is the largest "federal route" of nerve impulses in the brain.
The corpus callosum is white because it contains a lot of myelin, a fatty substance. This substance envelops the nerve cells, improving the conduction of impulses, and provides a quick exchange of information between the hemispheres.
People with congenital pathology of the corpus callosum are poorly oriented in social situations and have difficulty recognizing emotions.