Brain: structure, function, and biological significance
An overview of the brain — its main parts, cellular components, functions, protection, evolution, and why it matters for behaviour, cognition and health.
The brain is the central organ that controls perception, movement, internal regulation and many aspects of thought in animals with nervous systems. It receives information from the senses, integrates those signals and issues commands that guide behaviour and physiological processes. In humans the brain supports complex capacities such as language and abstract thinking, but many basic control functions — breathing, balance, and circulation — are also coordinated by brain structures shared across vertebrates.
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Major parts and cellular makeup
Macroscopically the brain is commonly described in terms of several major divisions: the large outer cerebral hemispheres, the cerebellum at the back of the skull, and the brainstem that links the spinal cord to higher centres. These regions contain networks of specialised cells. The signalling units are neurons, which communicate at junctions called synapses, while supporting cells called glia maintain the chemical environment and supply nutrients. Collections of neural pathways connect the brain with peripheral nerves that carry sensory information in and motor commands out.
Functions and behaviour
The brain organizes behaviour at many time scales. It detects and interprets sensory inputs, plans and executes movements, and adjusts organ function to maintain internal balance. Higher-level functions include learning, memory, emotion and decision-making. Neural circuits can change with experience — a property known as plasticity — allowing adaptation after injury or during learning. The brain also supports culture and technology in humans through capacities for symbolic thought, communication and cultural transmission.
Protection, development and energy use
Because it performs vital functions, the brain is well protected. In vertebrates the brain sits inside the protective casing formed by the bones of the skull and is cushioned by membranes and fluid. Cerebrospinal fluid and the meninges reduce mechanical shock and help remove waste. The brain develops from an embryonic neural tube and continues to change throughout life. It consumes a substantial share of the body's resources to maintain rapid electrical signalling and biochemical upkeep.
Evolutionary and taxonomic diversity
Brains evolved from simpler arrangements of nerve cells. Many invertebrates use distributed ganglia rather than a single centralized brain; octopuses have large, highly organized brains but also rely on peripheral control in their arms. Vertebrates show a trend toward increasing centralization and complexity, with expansion of the forebrain supporting sensory processing and complex behaviour. Some species have special adaptations: for example, a woodpecker protects its brain with anatomical features including a reinforced skull and a specialized tongue arrangement that helps dissipate shock during pecking.
Applications, disorders and study
Understanding the brain is central to medicine, psychology and artificial intelligence. Neurology and psychiatry address conditions ranging from stroke and epilepsy to mood and cognitive disorders; rehabilitation and training exploit brain plasticity. Researchers use imaging, electrophysiology and computational models to map function and dysfunction. Knowledge about the brain also informs education, robotics and public health, because brain health affects learning, productivity and quality of life.
Quick reference: major divisions
- Cerebrum: involved in perception, voluntary movement and higher cognition.
- Cerebellum: coordinates balance and fine motor control.
- Brainstem: regulates basic life-support functions and relays information to and from the spinal cord.
- Limbic structures: support emotion, motivation and memory formation.
The brain remains one of biology's most studied yet still mysterious organs. Progress in basic research and clinical practice continues to reveal how networks of cells generate behaviour, how they fail in disease, and how interventions can restore or enhance function.
Vertebrate brain
Function
The vertebrate brain processes highly differentiated sensory perceptions and coordinates complex behaviors. It is thus the repository for most of the complex information that the organism processes.
Not all information reaches the cortex and leads to consciousness. Peripheral nerve plexuses and especially centers in the brainstem process most of the excitations arriving from receptors unconsciously. Reflex arcs take on tasks that are completed at top speed and without conscious processing or delaying influence. In humans, there is also such an autonomic nervous system. It coordinates autonomic functions such as respiration, cardiovascular system, food intake, digestion and output, fluid intake and excretion, and reproduction.
Highly interconnected neurons interact in the brain (see neural network and excitation conduction). Its activity is studied in vivo by measuring brain waves via electroencephalography (EEG) and the electric fields produced by the brain via magnetoencephalography (MEG).
Evolution
In the course of evolution, the brain of "higher" animals has achieved a considerable degree of differentiation and internal organization (cerebralization). This is reflected in the mental and physical development of the individual (see embryology). The structure and, to a lesser extent, the volume of the brain correlate with learning ability and intelligence. Only in the hierarchy of the nervous system is the performance of the brain understandable.
In addition to vertebrates, squid possess highly complex brains that enable them to perform directed activities. In a broader sense, it is the central part of the nervous system of various invertebrates, such as annelids or insects. Depending on the type of brain, it is either a cerebral ganglion or a superior cerebral ganglion. Two groups of invertebrates have particularly complicated brains: arthropods (insects, crustaceans, and others), and cephalopods (octopuses, squid, and similar mollusks). The brains of arthropods and cephalopods arise from two adjacent nerve cords. Cephalopods such as the octopus and squid have the largest brains of any invertebrate.
The highly developed brain of vertebrates differs markedly from the rope ladder nervous system of arthropods. In insects, the digestive tract passes directly through the anterior nervous system (between the tritocerebrum and the subesophageal ganglion), so that the abdominal ganglia lie ventral (abdominal side) to the intestinal tube, whereas in vertebrates the spinal cord lies dorsal (dorsal side) to the intestine.
Structure
Different criteria can be decisive for a classification of the brain, so that different classifications into brain areas are possible, which do not have to be mutually exclusive. For a classification of the adult human brain, it can also be quite useful to take into account the knowledge gained from the study of its developmental steps.
For example, in the ontogenetic development of the human brain, after the neurulation of the central parts of the neural plate to form the neural tube as the early embryonic anlage of the central nervous system, successive stages in the formation of the brain become apparent in the further course. Thus, after the closure of the anterior opening of the neural tube at the end of the fourth week of development, three so-called primary cerebral vesicles are initially formed from the anterior third of the neural tube, the anlagen of prosencephalon, mesencephalon and rhombencephalon. They develop differently, so that five secondary brain vesicles can be distinguished in the over five-week-old embryo - these lead to the division of the brain into five main sections: telencephalon (end brain), diencephalon (midbrain), mesencephalon (midbrain), metencephalon (hindbrain) and myelencephalon (medullary brain).
| Week 4 | Week 5 | Week 6 - End of life | Ventricular system | |||
| Brain | anterior neural tube | TelencephalonEndbrain | Lateral ventricles | Rhinencephalon, amygdala, hippocampus, neocortex, basal ganglia | ||
| DiencephalonDiencephalon | Third ventricle | Thalamus dorsalis, | ||||
| MesencephalonMidbrain | MesencephalonMidbrain | mesencephalic aqueduct | Tectum (roof), | |||
| MetencephalonHindbrain | Fourth ventricle | Pons (bridge), | ||||
| MyelencephalonPosterior brain | Central Channel |
| ||||
The rough outline presented here follows the work of Pinel.
Other
In 2008, the remains of a 2500-year-old human skull were found on the grounds of the University of York (England), with most of its brain preserved. Researchers suspect that the brain of the man, who was probably 26-45 years old, has been so well preserved to this day partly because the head - no body was found - was buried in wet clay immediately after death. A complete explanation as to why the brain did not decay long ago has not yet been found.
Brain as a raw material is used in fat tanning.
Neurolinguistics studies how language is represented, processed and learned by the brain.
For brain diseases, see for example Central nervous system#Diseases.
Questions and answers
Q: What is the brain?
A: The brain is the part of the body which lets animals and humans think, and perform bodily functions, such as telling the rest of the body what to do. It gets input from sense organs, and changes behavior in response to this information. In humans, the brain also controls our use of language, and is capable of abstract thought.
Q: What does the brain control?
A: The brain is the main control centre of the whole body. It controls bodily functions such as movement, speech, emotions, memory and thinking.
Q: How is the brain made up?
A: The brain is made up of special cells called nerves, which are connected with each other and with other nerves in our body.
Q: How is it protected?
A: In all animals the brain is protected in some way. In ourselves, and all vertebrates, it is protected by the bones of the skull. In woodpeckers, for example, it is protected by their tongue which wraps around their brains.
Q: What does it do in humans?
A: In humans specifically, it controls our use of language and allows us to have abstract thought processes.
Q: Does it receive input from anywhere else?
A: Yes - it receives input from sense organs which helps inform its behaviour when responding to different stimuli or situations.
Related articles
Author
AlegsaOnline.com Brain: structure, function, and biological significance Leandro Alegsa
URL: https://en.alegsaonline.com/art/13660
Sources
- faculty.washington.edu : "Neuroscience For Kids - einstein's brain"