What differentiates the central and peripheral nervous system?

The nervous system can be defined as a set of organs and structures formed by nervous tissue, a tissue whose basic unit is the neuron, a type of highly specialized excitable cell. It also has other types of supporting cells and tissues, such as glial cells or the blood-brain barrier.

The nervous system originates from the ectoderm, the most distal or outer layer of the germ layers of the embryo, and this occurs in both diblastic animals (two germ layers) and triploblastic animals (three germ layers in the case of humans and the entire subkingdom). . bilateria which includes most animals).

The human nervous system is a very complex system that is responsible, in general terms, for capturing, processing, storing and transmitting information, as well as generating quick and coordinated responses between multiple organs when interacting with the environment, all using chemical signals and electrical.

To perform its function, the nervous system has organs and structures distributed throughout the body, including the brain, spinal cord and all the nerves that travel through the body. Depending on the distribution of these organs and structures, the nervous system can be studied in two major sections, the Central Nervous System and the Peripheral Nervous System.

central nervous system

The Central Nervous System (CNS) mainly consists of the brain and spinal cord; it can be said that it covers the part of the nervous system protected by bony structures. The brain is contained in the skull and the spinal cord in the vertebral column. The Central Nervous System also includes accessory tissues, such as the meninges, cerebrospinal fluid, or glial cells.

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Main structures of the central nervous system

The brain can be divided into three main regions: forebrain, midbrain, and hindbrain.

Forebrain: The main structures of the forebrain are the telencephalon, or cerebral croteza, and the diencephalon (epitalamus, thalamus, subthalamus, and hypothalamus). Midbrain or rhombencephalon midbrain: contains the metencephalon (cerebellum and pons) and myelencephalon (medulla oblongata).

Most muscle movements, sensory perceptions and executive functions They are located in the telencephalon. The brainstem, formed by the midbrain, pons and medulla, is the main communication route between the forebrain, spinal cord and peripheral nerves. In addition, it controls vital functions such as breathing, heart rate, sound localization and defensive physiological reflexes.

The spinal cord, the other major part of the Central Nervous System, is bounded by the medulla oblongata at the top. At the bottom, it ends at the first lumbar vertebra with the cauda equina, a group of nerves and nerve roots that will leave the spine to innervate organs of the pelvis and lower limbs.

The spinal cord transmits information from the brain to the peripheral nerves, it is the communication pathway between the peripheral nervous system and the brain. In addition, it is capable of developing its own effective responses, known as reflex responses, as they generally do not incorporate voluntary control.

The entire Central Nervous System is surrounded by the blood-brain barrier, a barrier of highly selective permeability that separates circulating blood from the extracellular fluid of the CNS.

peripheral nervous system

The Peripheral Nervous System (PNS) not protected by any specific bone structure It doesn’t even have a barrier. as the blood-brain barrier. It is made up of all the nerves and nerve ganglia outside the CNS.

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The SNP can be broken down based on several characteristics. One of the most common divisions separates peripheral nerves into motor, sensory, and autonomic nerves:

Motor nerves: These are nerves formed by motor neurons that innervate the muscles of different parts of the body. The somatic motor neurons they innervate the muscles of the musculoskeletal system and are usually voluntary actions. The visceral motor neurons they innervate the smooth muscles of the organs and are involuntary actions (they can be classified within the autonomic nerves). Sensory nerves: they transmit the information collected from the environment to the Central Nervous System, e.g. touch, temperature, pressure, proprioception, etc. Autonomic Nerves: These are nerves that are part of the Autonomic Nervous System, formed by the Sympathetic Nervous System and the Parasympathetic Nervous System. Both control the actions of organs and viscera, such as your muscles, glands or the tone of blood vessels, and have part made up of peripheral nerves and part of the Central Nervous System where information is processed and responses are elaborated.

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In yellow the CNS, in blue the PNS

Main differences

Both the Central and Peripheral Nervous System have neurons as a functional and structural basis. Both have similar physiology and share the way of transmitting information through electrical impulses and chemical signals across the synapse. The main differences between the two are in the proportion of support structures and the distribution of chemical signals used:

The central nervous system is protected by specific bone structures and the blood-brain barrier. The peripheral nervous system does not. The Central Nervous System is responsible for processing and storing information, as well as developing executive responses. The Peripheral Nervous System focuses more on transmission of information between different areas, such as the transmission of sensory information collected from the environment or internal organs to the CNS, or the transmission of orders from the CNS to the effector organs. An injury to the PNS will cause a problem located in the area supplied by damaged nerves. An injury to the CNS can lead to global problems and large areas. For example, a nerve branch injury can affect one limb, while a spinal cord injury can affect both limbs, even with intact peripheral nerve branches. Numerous neurotransmitters are involved in the Central Nervous System: acetylcholine, norepinephrine, glutamate, GABA, dopamine, serotonin, etc. Only two are involved in the Peripheral Nervous System: acetylcholine and norepinephrine.

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