Neuroglia
Neuroglia, also known as glial cells, are essential components of the nervous system, often referred to as "nerve glue" due to their role in supporting and connecting neurons. Outnumbering neurons by approximately ten to one, neuroglia fulfill various critical functions, including providing nutrients, maintaining homeostasis, and facilitating signal transmission. While neurons are responsible for sending electrical impulses, neuroglia do not communicate via electrical signals; instead, they interact with neurons by absorbing and responding to chemical signals.
There are four main types of neuroglia: astrocytes, oligodendrocytes, microglial cells, and ependymal cells. Astrocytes support neurons, regulate chemical balance, and form the blood-brain barrier, which protects the central nervous system (CNS). Oligodendrocytes are involved in the formation of myelin, a protective sheath around neuron axons that enhances signal transmission. Microglial cells act as immune defenders in the CNS, removing dead cells and potentially harmful pathogens, though they may also play a role in certain neurodegenerative diseases. Lastly, ependymal cells line the brain's ventricles and the spinal canal, producing and managing cerebrospinal fluid that nourishes and protects the CNS. Understanding neuroglia is vital, as they play increasingly recognized roles beyond mere support of neurons, influencing overall nervous system health and function.
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Neuroglia
Neuroglia are cells that are part of the nervous system. The word neuroglia means "nerve glue." These cells got their name because they help connect and bind together all the cells in the nervous system, though they also play other vital roles. Neuroglia and neurons are the types of cells that make up the nervous system. Neuroglia—also called glial cells or glia—help provide nutrients and support to neurons. They outnumber neurons in the body by about ten to one. Neurons are the cells that send electrical signals throughout the body. Neuroglia provide neurons with the support they need to send the signals, and they help maintain homeostasis. Different types of neuroglia perform different functions in the body.
Background
The nervous system sends nerve impulses to different parts of the body. The central nervous system (CNS) is the main part of the nervous system, and it includes the brain and spinal cord. The CNS is made up of two types of cells: neurons and neuroglia. Neurons are the cells that send electrical impulses and form synapses among one another. They can send motor information and sensory information to and from the brain. For example, neurons are responsible for sending signals from the brain to the muscles to create movement. They are also responsible for receiving information from parts of the body to tell the brain about pain and other sensations. Neurons have three main parts. The cell body includes the nucleus and organelles. The dendrites branch out from the cell body and mainly receive electrical impulses from other cells. The axon stems out from the cell body in the opposite direction of the dendrites and mostly sends electrical signals to other cells. The axons can be quite long.
The other cells in the CNS are neuroglia. Neuroglia play many roles in the CNS. They are best known for supporting neurons by protecting them and providing them with nutrients. Neuroglia are often smaller than neurons, but they outnumber neurons in the body. Many more neuroglia are necessary to help support the neurons. Neuroglia are also different from neurons because they maintain the ability to divide, or reproduce.
Overview
Neuroglia are best known for supporting neurons in the nervous system. Yet, scientists are learning that these cells play other important roles as well. Neuroglia help send signals in the nervous system. They do not communicate among one another or other cells using electrical signals as neurons do; however, they "listen" to other cells by absorbing chemicals. When neurons send chemicals to one another, neuroglia receive some of the chemicals too. Scientists have learned that neuroglia sometimes strengthen signals sent by neurons in response to their "listening." Furthermore, neuroglia are required for neurons and synapses to function properly. Another vital role of neuroglia is that these cells clean up dead nerve cells and other debris in the nervous system.
Four types of neuroglia exist: astrocytes, oligodendrocytes, microglial cells, and ependymal cells. Astrocytes are located in the brain and the spinal cord. These cells have a cell body with many branching thread-like projections. Two different types of astrocytes exist: protoplasmic and fibrous. Protoplasmic astrocytes are located mostly in the gray matter of the CNS. They help balance chemicals so that signaling can occur effectively in the brain. These astrocytes can also join to form sheets that surround and protect neurons. Fibrous astrocytes are found mostly in the white matter. These cells have fewer but much longer projections. They also have feet that can attach to blood vessels, synapses, and other structures.
Astrocytes play a number of roles in the nervous system. Neurons need certain chemicals and nutrients to function properly, and astrocytes provide some of the nutrients and chemicals by transporting certain molecules into and out of the interstitial fluid (the fluid between cells in the brain). Astrocytes also help heal injuries to the nervous system. When an injury occurs, the astrocytes reproduce to heal the area. Additionally, astrocytes help make up blood-brain barrier (BBB), a structure in the body that regulates the molecules that come into and out of the CNS. It acts as a barrier between the blood and the neural cells. This helps the CNS maintain homeostasis. Astrocytes play an important role in maintaining the BBB's ability to keep out molecules, ions, and other materials that could disrupt the nervous system's homeostasis.
Oligodendrocytes are located in both the white and gray matter. They have fewer roles to play in the CNS, but they are also very important. Oligodendrocytes help form myelin that covers the axons of neurons. Myelin is a white material made mostly of lipids and proteins that covers and protects axons. The myelin also helps the axons send electrical impulses because it insulates them. Oligodendrocytes have cell bodies. They also have projections that branch out from the cell body. The myelin forms at the ends of these projections. One oligodendrocyte can help form the myelin sheath for more than one axon, as each oligodendrocyte may have many projections.
Microglial cells are immune cells in the CNS. They can identify and destroy some pathogens. They also remove dead cells. Although microglial cells are vital for the health of the CNS, scientists believe they may play a part in some neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease. These disorders might cause the microglial cells to destroy or harm healthy cells or synapses in the brain. Scientists are investigating microglial cells and their in role in the body so they can better understand how they might contribute to certain diseases.
Ependymal cells line ventricles in the brain and the canal in the spinal cord. These spaces in the brain and spinal cord are filled with cerebral spinal fluid (CSF). The CSF is fluid that protects and provides nutrients to the CNS. The ependymal cells create a barrier between the CSF and the fluid inside the brain. The ependymal cells also help create, secrete, and move CSF.
Bibliography
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