Looking at the Neuron; Its structures and their functions.
Cell body. There are around 100 billion neurons in the brain! Neurons are really small, measuring in microns (thousands of a millimetre) The smallest neuron measures around 4 microns (.004mm) and the largest measures 100 microns (.1mm). Neurons (also known as nerve cells) play an important role in controlling bodily functions, movements, emotions and cognition. Here’s all you need to know about the role and structure of a neuron; neuron dysfunction and cell death.
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Neurons are the building blocks of the central nervous system. A neuron’s primary role is to communicate information. It communicates via electrical impulses or using specific chemicals such as neurotransmitters (what are the different types of neurotransmitters?). The neuron has 3 distinct parts. The dendrites, the cell body and the axon. Each structure plays a specific role in ensuring neurons are able to send and receive signals and connect with other neurons.
The dendrites are connected to the cell body. They conduct messages from axon of other neurons and pass the message onto the cell body. The cell body sits between the dendrites and the axon. It determines the strength of the message it receives from the dendrites. If it is strong enough, it will send the message down the axon. The axon is connected to the cell body. It conducts the message from the cell body and passes it on to other neurons.
Dendrites are branch-like structures structures surrounding the cell body. They receive electrical and chemical messages from other neurons, which are collected in the cell body. These messages are either inhibitory or excitatory in nature. If the message is inhibitory, the cell body will not transmit the message to the axon. However, if the message is excitatory in nature, then the cell body will send the message down the axon and pass it to other neurons.
The cell body (or Soma)
Also known as the soma, the cell body is a ball-like structure. It contains the control centre of the neuron, also known as the nucleus. Together, the cell body and the nucleus control the functions of the nerve cell. To be able to do this, the cell body contains organelles, or really tiny organs in the nucleus. Each organelle has a unique job.
First and foremost, the most important organelle, the nucleus, regulates all cell functions. It also contains the cell’s DNA, which is essentially the neuron’s blueprint. The nucleus is another organelle that serves a vital purpose to the functioning of the neuron. It nucleolus produces ribosomes, which are essential to protein production. The cell body is also home to the endoplasmic reticulum, golgi apparatus and mitochondria. The mitochondria is the neuron’s fuel source, it produces all the energy needed for the nerve cell to function properly. The endoplasmic reticulum and the golgi apparatus, work together, with the rest of the organelles in the nucleus to produce and transport protein.
The protein produced by the cell body, are the key ingredients, to build new dendrites. Building new dendrites enables the neuron to make new connections with other neurons. As well as making proteins, the cell body is also responsible for making chemicals, also known as neurotransmitters, which neurons use as signals. Neurotransmitters can serve and inhibitory or excitatory function to the neuron.
The axon is long and slender, and it projects electrical impulses away from the cell body. The axon communicates with other neurons. When the electrical or chemical message reaches the axon terminal (end of the axon), The axon terminal release neurotransmitters into the synapse (small junction between two neurons). The neuron uses the synapse to communicate and send messages to other nerve cells.
Cell death and Neurodegeneration
Neurodegeneration is when the neuron loses its structure or ability to function properly. Damage to different parts of the neuron i.e. the cell body, dendrites or axon, can lead to a range of different neurodegenerative diseases. Parkinson’s disease, Alzheimer’s disease, Huntington’s disease and multiple sclerosis are as a result of neuron damage or death. Cell death, is the death of neurons. Once this occurs, nerves cells do not regenerate.
Two types of cell death
Apoptosis. This type of cell death is highly controlled and regulated and is often predictable. It is genetically programmed, and is a normal part of our bodily functions. Every day our bodies make new cells and kill off older cells to make room. When the processing of killing cells goes wrong, one of two things happen; the body doesn’t kill enough cells, or the body kills too many. The former leads to uncontrolled growth and can result in cancer. The latter leads to excessive cell death, a common cause of neurodegenerative diseases.
Necrosis. This type of cell death is also known as unnatural cell death. This means cell death isn’t a results of natural causes, like our bodies removing unwanted cells, but rather that the damage is a result of external force. This could be trauma, injury, virus, or reduced blood or oxygen supply. Necrosis leads to inflammation, which can spread and cause further damage. An example of cell death by necrosis is a stroke.
Nerve cell death in specific brain regions and neurodegenerative diseases
Huntington’s Disease is triggered by a genetic mutation. The mutation gives rise to an overproduction of the neurotransmitter glutamate. This leads to the death of neurons in the basal ganglia, which has been associated with causing uncontrollable movement.
Alzheimer’s Disease is caused by the build-up of beta amyloid and tau proteins around neurons in a few parts of the brain, like the neocortex and hippocampus. This leads to a reduced ability to carry out everyday tasks.
Cell body dysfunction
The cell body is responsible for controlling the neuron. It contains organelles which produce energy, protein and neurotransmitters for the nerve cell. When the cell body malfunctions in can results in no longer produce energy and protein in a way that is good for the neuron and the brain.
The mitrochondria, a small organelle in the cell body, is the neuron’s energy source. As the brain has extremely high energy demands, the nerve cell’s mitchondrial function needs to meet them. Mutations in the DNA of mitochondria, results in mitochondrial dysfunction. This has been linked to neurodegenerative diseases, such as Alzheimer’s, Parkinson’s, Huntington’s and Amyotrophic Lateral Sclerosis (Motor neuron disease).
Neuron’s are extremely small, but they have a mighty role to play. The dendrites, cell body and axon all play a vital role in brain communication and function. However, cell death or cell dysfunction can have a huge impact on our brains and can affect our ability to function. It is quite frankly amazing how such a small structure carries out.
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