The central nervous system (CNS) is comprised of the brain and spinal cord. The three broad functions of the CNS are to take in sensory information, process information, and send out motor signals. Show
The CNS receives sensory information from the nervous system and controls the body's responses. The central nervous system plays a primary role in receiving information from various areas of the body and then coordinating this activity to produce the body's responses. The CNS is differentiated from the peripheral nervous system, which involves all of the nerves outside of the brain and spinal cord that carry messages to the CNS. This article discusses the structures that make up the central nervous system and how they function. It also explores some of the diseases and conditions that can affect the CNS. Central Nervous System StructureThe CNS has three main components: the brain, the spinal cord, and the neurons (or nerve cells). Each part of the CNS plays an important role in how the body functions, and the three components of the CNS work together to take in information and control how the body responds. The BrainThe brain controls many of the body's functions including sensation, thought, movement, awareness, and memory. The surface of the brain is known as the cerebral cortex. The surface of the cortex appears bumpy thanks to the grooves and folds of the tissue. Each groove is known as a sulcus, while each bump is known as a gyrus. The largest part of the brain is the cerebrum. It is responsible for functions such as memory, speech, voluntary behaviors, and thought. The cerebrum is divided into two hemispheres, the right hemisphere and the left hemisphere. The right hemisphere controls movements on the body's left side, while the left hemisphere controls movements on the body's right side. While some functions do tend to be lateralized, researchers have found that there are not "left brained" or "right brained" thinkers, as the old myth implies. Both sides of the brain work together to produce various functions. Each hemisphere of the brain is then divided into four interconnected lobes:
Other important areas of the brain include the basal ganglia, cerebellum, Broca's area, corpus callosum, medulla oblongata, hypothalamus, thalamus, and amygdala. RecapThe brain is the part of the central nervous system that controls many of the functions of the body, including movement, thought, learning, and awareness. Spinal CordThe spinal cord connects to the brain via the brain stem and then runs down through the spinal canal, located inside the vertebrae. The spinal cord carries information from various parts of the body to and from the brain. While it varies from one individual to the next, the spinal cord is about 18 inches in length. At the brainstem, 31 spinal nerves enter into the spinal cord. The nerves of the spinal cord consist of:
In the case of some reflex movements, responses are controlled by spinal pathways without involvement from the brain. Examples include the Golgi tendon reflex, the crossed extensor reflex, and the stretch reflex. RecapThe spinal cord carries information from the brain to the rest of the body and transmits signals from the body to the brain. NeuronsNeurons are the building blocks of the central nervous system. Billions of these nerve cells can be found throughout the body and communicate with one another to produce physical responses and actions. Neurons are the body's information superhighway. An estimated 86 billion neurons can be found in the brain alone. Most neurons are divided into three basic sections: dendrites, cell body, and axon. These cells also differ in terms of function. The three types of neurons are afferent neurons, efferent neurons, and interneurons. Efferent neurons are motor neurons that carry signals from the brain to the peripheral nervous system. Afferent neurons are sensory neurons that bring information from the senses to the brain. Interneurons are association neurons that connect efferent and afferent neurons to the central nervous system. RecapNeurons are the cells that make up the central nervous system. They are responsible for communicating information throughout the body. Protective StructuresSince the CNS is so important, it is protected by a number of structures. First, the entire CNS is enclosed in bone. The brain is protected by the skull. The spinal cord is encased by the vertebrae that make up the spinal column. The brain and spinal cord are both covered with a protective tissue known as meninges. There are three layers of meninges protecting the brain and spinal cord:
The entire CNS is also immersed in a substance known as cerebrospinal fluid, which forms a chemical environment that allows nerve fibers to transmit information effectively as well as offering yet another layer of protection from potential damage. RecapThe CNS is protected by structures including the skull, spinal vertebrae, meninges, and cerebrospinal fluid. Diseases of the Central Nervous SystemThere are a number of problems and diseases that can affect the CNS. Damage or disease to the central nervous system can produce a range of effects. Some of the conditions that can impact the CNS include:
RecapA variety of diseases and other problems can affect the CNS, including infections, trauma, tumors, and degenerative conditions. Such diseases and damage can lead to impairment and sometimes death. What Is Central Nervous System (CNS) Depression? Frequently Asked Questions
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