Microglia
Microglia are a specialized type of neuroglia, functioning as the primary immune cells within the central nervous system (CNS), which comprises the brain and spinal cord. These small cells play a crucial role in protecting the CNS by detecting and eliminating pathogens, clearing away dead cells, and supporting overall neural health. Microglia originate from the mesoderm, unlike other neuroglia that arise from the neuroectoderm, which informs their unique immune functions.
In their resting state, microglia monitor their environment with spindly projections, but when they encounter threats, they transform into active microglia, characterized by a larger size and a more defined role in the immune response. While essential for maintaining homeostasis, prolonged activation of microglia can lead to inflammation and potential damage to healthy neurons, particularly in neurodegenerative diseases like Alzheimer’s and Parkinson's.
Recent research is focusing on the dual roles of microglia, both protective and potentially harmful, as scientists strive to understand how to leverage their functions to promote healing and address CNS disorders. As they are pivotal in shaping neural activity and monitoring synaptic function, microglia remain a critical area of study in neuroscience.
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Microglia
Microglia are a type of neuroglia, or glial cell. Microglia are located in the central nervous system (CNS). These cells are the main immune cells of the CNS. They help attack and destroy pathogens in the CNS, and they help clear away dead cells in the system. Microglia may also play a role in the development of some diseases and disorders, such as Alzheimer's disease, that affect the CNS. Microglia got their name because they are the smallest neuroglia.
Background
Microglia are cells in the CNS. The CNS is the system that sends sensory and motor signals between the brain and the rest of the body. It is made up of the brain and spinal cord. The types of cells that make up matter in the CNS are neurons and neuroglia. Neurons are the cells that send electrical impulses and messages to and from the brain. Many types of neurons exist, but they all have the same basic structure. The main part of the neuron is the cell body, which includes a nucleus. Dendrites are thread-like projections that branch out from one side of the neuron. These projections are relatively small, and they receive information from the axons of other neurons. Each neuron has one axon that projects out from the other side of the cell body. The axons can be quite long, and they transmit the electric impulse from one neuron to the next. Neuroglia are the other type of cell in the CNS. Neuroglia include astrocytes, oligodendrocytes, microglia, and ependymal cells. These different types of neuroglia play different roles in the CNS, but neuroglia are best known for supporting neurons, which send the electrical impulses in the CNS. Scientists are beginning to understand that some neuroglia also play a role in communicating signals in the brain. Neuroglia are vital to the function of the CNS, and they outnumber neurons about ten to one. Without the neuroglia, the neurons would not be able to function.
Overview
As neuroglia, microglia have been best known for their support of the neurons in the CNS. Although some neuroglia provide nutrients to neurons or give them physical support, microglia are best known for being the immunological cells in the CNS. These cells help protect other cells in the CNS from pathogens and other dangers. As immune cells, microglia originate in the same way other immune cells in the body do, and they do not originate in the same place other neuroglia do. Most neuroglia originate from the embryonic layer called the neuroectoderm; however, microglia most likely originate from the embryonic layer called the mesoderm. This is the same layer where other immunological cells originate. By understanding where the microglia originate, scientists can better understand their function in the body.
Microglia have a specific form that also helps differentiate them from other neuroglia. These cells have a main cell body that includes a nucleus. The nucleus is dark and elongated. They also have irregularly shaped bodies. Most microglia have small, spindly projections that branch out from the cell body. They are usually found adjacent to neurons, though they are often separated from neurons by projections of astrocytes, another type of neuroglia. Microglia are in this shape until they have to take action. Then they convert from resting microglia to active microglia.
Microglia are vital to maintaining homeostasis and keeping the CNS healthy, and they make up about 12 percent of entire CNS. They help protect the CNS from pathogens and repair damage. When the microglia detect unwanted substances in the CNS, they react similarly to other immune cells, or microphages. Microglia are a type of microphage. Microphages are located throughout the body, and they help rid the body of toxins and dead cells.
Microglia use their projections to monitor the fluid around them. They check for dead or damaged cells, foreign cells, or CNS damage or inflammation. If the microglia finds one of these warning signs, they will transform into active microglia. Active microglia look different from resting microglia. They became larger and lose definition. They travel to the site of the injury or infection. Microglia can secrete cytokines and chemokines, which are chemicals that can kill pathogens. Then the microglia perform phagocytosis. In this process, they break up and consume dead cells. This important function helps keep the CNS clear of debris. If microglia remain active for too long, they can cause dangerous inflammation in the brain. This prolonged inflammation can cause cell dysfunction or even cell death.
Although microglia play a vital role in maintaining a healthy CNS, these cells can also cause damage. In a typical CNS, microglia destroy only harmful cells and pathogens. Furthermore, they consume only dead cells and debris. However, in the CNS of a person with a disease such as Alzheimer's disease, microglia may kill or destroy healthy cells. Scientists are still learning about the role of microglia in diseases such as Alzheimer's disease and Parkinson's disease. They hope to prevent or treat these types of diseases by studying microglia and their functions.
Microglia are best known for their role in the CNS's immune response, but they also have other functions. Scientists have found that the microglia interact with neurons. They help shape neural activity when they are in their resting form. Microglia seem to be especially involved in monitoring the function of synapses in the brain. Scientists must learn more to fully understand the role of microglia in the brain. Some scientists hope that humans will one day be able to harness the power of the microglia to help heal the brain and reverse damage from disease.
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