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The Mysterious Brain: How It Becomes the Control Center of Animal Nervous Systems
The brain is the central organ of the nervous system of all vertebrates and most invertebrates. The brain is composed of nervous tissue and is usually located in the head, often near special sense organs such as vision, hearing, and smell. As the most specialized organ, the brain is responsible for receiving information from the sensory nervous system, processing this information (thinking, cognition, and intelligence), and coordinating motor control (muscle activity and the endocrine system).
While invertebrate brains arise from paired segmental ganglia (each ganglion responsible for only a corresponding body segment) from the ventral nerve cord, vertebrate brains develop from the midline dorsal nerve cord, forming The expansion of the head end of the neural tube provides centralized control over all body segments.
The brains of all vertebrates can be divided in embryonic development into three parts: the forebrain (forebrain, further subdivided into the telencephalon and diencephalon), the midbrain (midbrain), and the hindbrain (hindbrain, further subdivided into For the hidden brain and medullary brain). The spinal cord interacts directly with bodily functions below the head and can be considered a caudal extension of the myelometrial brain embedded in the spinal column. The brain and spinal cord together form the central nervous system in all vertebrates.
In the human body, the cerebral cortex contains approximately 14 billion to 16 billion neurons, while the estimated number of neurons in the cerebellum is between 55 billion and 70 billion. Each neuron is connected to thousands of other neurons by synapses, often communicating through cytoplasmic processes called dendrites and axons. Axons are usually myelinated and transmit rapid pulses of tiny electrical signals called action potentials to other brain areas or to specific receptor cells in distant parts of the body.
The prefrontal cortex controls executive functions and is particularly well developed in humans. From a physiological perspective, the brain exerts centralized control over other organs. They do this both by generating patterns of muscle activity that affect the rest of the body, and by driving the secretion of chemicals called hormones.
This centralized control allows the brain to respond quickly and coordinatedly to changes in the environment. Some basic response abilities, such as reflexes, can be mediated by the spinal cord or peripheral ganglia, but precise control of meaningful behavior based on complex sensory input requires the concentrated brain's information integration capabilities. The workings of single brain cells are now well understood, but how they collaborate among millions of cells remains unresolved.
Some models in modern neuroscience view the brain as a biological computer whose mechanisms are distinct from, but similar to, those of a digital computer in that it can acquire information from the world around it, store it, and use it in a variety of ways way to process information. This article compares the properties of the brain across the entire range of animal species, with the greatest focus on vertebrates. The article also touches on the human brain because it shares many properties with other brains.
However, the human brain differs from other brains in ways that are specifically detailed in the text. In any case, a more in-depth exploration of these topics will be provided in the article on the human brain.
Structure of the brain
Brain shape and size vary greatly between species, and identifying common features is often difficult. However, there are some general principles of brain architecture that apply across species. Some aspects of brain structure are common across nearly all animal species; others distinguish "advanced" brains from more primitive ones, or between vertebrates and invertebrates.
The simplest way to obtain information about brain anatomy is visual inspection, but a variety of more sophisticated techniques have been developed. Because brain tissue is too soft in its natural state, it can be hardened by soaking in alcohol or other fixatives and then cut to examine its interior. The interior of the brain can be seen as areas of so-called gray matter - darker in color - separated by areas of white matter (lighter in color).
Cell structure
The brains of all species are primarily composed of two major types of brain cells: neurons and glia. Glial cells (also called glial cells or glial cells) come in several different types and perform a variety of key functions, including structural support, metabolic support, insulation, and developmental guidance. However, neurons are often considered the most important cells in the brain. The human cortex contains approximately 14 billion to 16 billion neurons, while the number of neurons in the cerebellum is estimated to be between 55 billion and 70 billion.
Each neuron is connected to thousands of other neurons through synapses. Neurons are unique in their ability to send signals to specific target cells, sometimes over long distances. They send these signals through the axon, a slender fiber of protoplasm extending from the cell body, often projecting in the form of many branches to other areas, whether adjacent or distant.
Understanding the vertebrate brain is a complex process because it involves millions of cells and the delicate and complex communication mechanisms between them. Does this make you think: What unsolved mysteries are there waiting for us to uncover in the evolution of the brain?
