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The nervous system consists of the central nervous system (brain and spinal cord) and peripheral nervous system (nerve fibers that attach to and lie outside the brain and spinal cord). There are a number of differences between the CNS and PNS; one difference is the size of the cells. Central Nervous System Structure The Brain. Degeneration: in some cases, the spinal cord or brain can degenerate. This is because they do not synapse first on peripheral ganglia, but directly on CNS neurons. The brain is only required to stop and start the process, or make changes if, for instance, an object appears in your path. There are many CNS diseases and conditions, including infections such as encephalitis and poliomyelitis, early-onset neurological disorders including ADHD and autism, late-onset neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and essential tremor, autoimmune and inflammatory diseases such as multiple sclerosis and acute disseminated encephalomyelitis, genetic disorders such as Krabbe's disease and Huntington's disease, as well as amyotrophic lateral sclerosis and adrenoleukodystrophy. The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of … Thalamus: positioned in the center of the brain, the thalamus receives sensory and motor input and relays it to the rest of the cerebral cortex. The central nervous system is one of the two major divisions of the nervous system. Without glial cells, developing nerves often lose their way and struggle to form functioning synapses. [9], The hippocampus is involved in storage of memories, the amygdala plays a role in perception and communication of emotion, while the basal ganglia play a major role in the coordination of voluntary movement.[9]. The peripheral nervous system consists of all body nerves. [8] The spinal cord reaches from the base of the skull, continues through[8] or starting below[10] the foramen magnum,[8] and terminates roughly level with the first or second lumbar vertebra,[9][10] occupying the upper sections of the vertebral canal. The tectum, pretectum, cerebral peduncle and other structures develop out of the mesencephalon, and its cavity grows into the mesencephalic duct (cerebral aqueduct). [20] The basic pattern of the CNS is highly conserved throughout the different species of vertebrates and during evolution. Central nervous system (CNS): The central nervous system is that part of the nervous system that consists of the brain and spinal cord. The brain is roughly split into four lobes: Temporal lobe (green): important for processing sensory input and assigning it emotional meaning. The cerebrum is divided into two hemispheres which are connected by the corpus callosum. [6] Within the CNS, the interneuronal space is filled with a large amount of supporting non-nervous cells called neuroglia or glia from the Greek for "glue". Bottom image: CNS seen in a median section of a 3 month old embryo. More detail and supporting information is in the main article. [7], The CNS consists of the two major structures: the brain and spinal cord. Stroke: a stroke is an interruption of blood supply to the brain; the resulting lack of oxygen causes tissue to die in the affected area. However, many higher functions — reasoning, problem-solving, creativity — involve different areas working together in networks. [23], Schematic diagram showing the central nervous system in yellow, peripheral in orange. [9], The next structure rostral to the medulla is the pons, which lies on the ventral anterior side of the brainstem. Planarians, members of the phylum Platyhelminthes (flatworms), have the simplest, clearly defined delineation of a nervous system into a CNS and a PNS. [12][13][citation needed], The brainstem consists of the medulla, the pons and the midbrain. It is the largest white matter structure in the brain and allows the two hemispheres to communicate. [4] A large portion of the brainstem is involved in such autonomic control of the body. [11] The CNS is composed of white and gray matter. The thalamus acts as a linkage between incoming pathways from the peripheral nervous system as well as the optical nerve (though it does not receive input from the olfactory nerve) to the cerebral hemispheres. [9], Apart from its function of sorting information from the periphery, the thalamus also connects the cerebellum and basal ganglia with the cerebrum. Thalamus, For instance, if the brain of a cat is separated from its spine so that its brain has no contact with its body, it will start spontaneously walking when placed on a treadmill. MNT is the registered trade mark of Healthline Media. The peripheral nervous system (PNS) connects the central nervous system … When damaged, an individual finds it difficult to speak but can still understand speech. Medulla oblongata: extending below the skull, it is involved in involuntary functions, such as vomiting, breathing, sneezing, and maintaining the correct blood pressure. [4], The brain (cerebrum as well as midbrain and hindbrain) consists of a cortex, composed of neuron-bodies constituting gray matter, while internally there is more white matter that form tracts and commissures. All in all 31 spinal nerves project from the brain stem,[9] some forming plexa as they branch out, such as the brachial plexa, sacral plexa etc. The brain is the center of thoughts and interpret the signals that comes from the external stimulus in the environment. Central and peripheral nervous systems are the two components of the nervous system in animals. Oligodendrocytes: responsible for creating the myelin sheath — this thin layer coats nerve cells, allowing them to send signals quickly and efficiently. The author Michael Nikoletseas wrote: The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. Schematic image showing the locations of a few tracts of the spinal cord. If the cerebellum is damaged, the primary symptom is disrupted motor control, known as ataxia. The nervous system is responsible for sending, receiving, and interpreting information from all parts of the body. The autonomic system is subdivided into the sympathetic and parasympathetic systems. The brain is the central control module of the body and coordinates activity. Now we will look at some of the parts of the CNS in more detail, starting with the brain. During early development of the vertebrate embryo, a longitudinal groove on the neural plate gradually deepens and the ridges on either side of the groove (the neural folds) become elevated, and ultimately meet, transforming the groove into a closed tube called the neural tube. Radial glia: act as scaffolding for new nerve cells during the creation of the embryo’s nervous system. [9] [21] Corpus callosum: a broad band of nerve fibers that join the left and right hemispheres. The brain can be divided into four main lobes: temporal, parietal, occipital and frontal. The spinal cord reaches from the base of the skull, continues through or starting below the foramen magnum, and terminates roughly level with the first or second lumbar vertebra, occupying the upper sections of the vertebral canal. Pineal gland, It is often the main structure referred to when speaking of the nervous system in general. The central nervous system consists of the brain and the spinal cord. Third ventricle, Tectum, These connections have been shown by the use of medical imaging techniques, such as functional MRI and Positron emission tomography. Additionally, parts of the visual and auditory systems are located in the midbrain, including control of automatic eye movements. [22] The spinal cord is continuous with the brain and lies caudally to the brain. [9], The brainstem also holds the reticular formation, a group of nuclei involved in both arousal and alertness. The neural stem cells, principally radial glial cells, multiply and generate neurons through the process of neurogenesis, forming the rudiment of the CNS.[15]. The metencephalon becomes, among other things, the pons and the cerebellum, the myelencephalon forms the medulla oblongata, and their cavities develop into the fourth ventricle.[9]. As such, the olfactory epithelium is the only central nervous tissue in direct contact with the environment, which opens up for therapeutic treatments. We will look at the types of cells involved, different regions within the brain, spinal circuitry, and how the CNS can be affected by disease and injury. Their primitive brains, consisting of two fused anterior ganglia, and longitudinal nerve cords form the CNS; the laterally projecting nerves form the PNS. Another major difference between the CNS and PNS involves regeneration (regrowth of cells). All rights reserved. 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