What is a neuron? Function, classification, structure

Neurons are called neurons. They have three distinct parts, including the cell body, axon, and dendrites. These parts help them send and receive chemical and electrical signals.

1. What is a Neuron?

Neurons, also known as neurons, send and receive signals from your brain. Although nerve cells have a lot in common with other cell types, they have distinct structures and functions.
Specialized dendrites called axons allow neurons to transmit electrical and chemical signals to other cells. Neurons can also receive these signals through stem-like extensions called dendrites.
At birth, the human brain consists of an estimated 100 billion neurons. Unlike other cells, neurons do not reproduce or regenerate. They are not replaced when they die.
The creation of new nerve cells is called neurogenesis. Although this process is not well understood, it can occur in certain parts of the brain after birth.
As researchers gain insight into both neurons and neurogenesis, many are also working to uncover links to neurodegenerative diseases like Alzheimer's and Parkinson's.

2. Parts of a nerve cell

Neurons vary in size, shape and structure depending on their role and location. However, nearly all neurons have three essential parts: cell body, axon, and dendrites.

2.1. Cell body

Also known as the soma, the cell body is the core of the neuron. Cell bodies carry genetic information, maintain the structure of neurons, and provide energy to drive activities.
Like other cell bodies, somatic neurons contain a nucleus and specialized organelles. It is enclosed by a membrane that both protects it and allows it to interact with its surroundings.

2.2. Axon

The axon is a long, tail-like structure that joins the cell body at a specialized junction known as the axon thalamus. Many axons are isolated by a fatty substance called myelin. Myelin helps axons conduct electrical signals. Nerve cells generally have an axon.

Neuron thần kinh là gì? Chức năng, phân loại, cấu trúc — Sợi trục là một cấu trúc dài, giống như đuôi, kết hợp với cơ thể tế bào tại một điểm nối chuyên biệt được gọi là đồi sợi trục

2.3. dendrites

Dendrites are fibrous roots that branch out from the cell body. Like antennae, dendrites receive and process signals from the axons of other neurons. Neurons can have more than one set of dendrites, called dendrites. In general, how many they have depends on their role.
For example, Purkinje cells are a special type of nerve cell found in the cerebellum. These cells have highly developed dendrites that allow them to receive thousands of signals.

3. Function of nerve cells

Neurons send signals using action potentials. An action potential is the change in the electrical potential of a neuron caused by the flow of ions into and out of the nerve membrane.
Action potentials can activate both chemical and electrical synapses.

3.1. Chemical neural synapses

In chemical synapses, action potentials affect other neurons through a space between neurons called a synapse. Neurosynapses include a presynaptic terminus, a synaptic cleft, and a postsynaptic terminus.
When an action potential is generated, it is carried by the axon to a presynaptic terminus. This triggers the release of chemical messengers called neurotransmitters. These molecules cross the synaptic cleft and bind to receptors at the postsynaptic end of a dendrite.
Neurotransmitters can stimulate the postsynaptic neuron, causing it to generate an action potential on its own. In addition, they can inhibit the postsynaptic neuron, in which case it does not generate an action potential.

3.2. Electrical nerve synapse

Electrical synapses can only be excitable. They occur when two neurons are connected through a gap junction. This gap is much smaller than that of a neural synapse and consists of ion channels that help direct the transmission of positive electrical signals. As a result, electrical synapses are much faster than chemical synapses. However, the signal fades from one neuron to the next, making them less efficient to transmit.

4. Types of nerve cells

Neurons differ in structure, function and genetic makeup. With the sheer number of neurons, there are thousands of different types, just like there are thousands of species of living things on Earth.
Functionally, scientists classify neurons into three broad categories: sensory, motor, and mid-neurons.

4.1. Sensory neurons

Sensory neurons help you:
Taste, Hearing, Hearing, and Perception Sensory neurons are activated by physical and chemical inputs from your environment. Sound, touch, heat, and light are physical inputs. Smell and taste are input chemicals.
For example, stepping on hot sand activates sensory neurons in the soles of your feet. Those neurons send a message to your brain, helping you perceive heat.

4.2. Motor neurons

Motor neurons have a motor role, including both voluntary and involuntary movements. These nerve cells allow the brain and spinal cord to communicate with muscles, organs, and glands throughout the body.
There are two types of motor neurons: inferior and superior. Lower motor neurons carry signals from the spinal cord to smooth and skeletal muscle. Upper motor neurons carry signals between your brain and spinal cord.
For example, when you eat, lower motor neurons in your spinal cord send signals to smooth muscles in your esophagus, stomach, and intestines. These muscles contract, allowing food to move through your digestive tract.

4.3. Interneurons

Interneurons are nerve mediators found in your brain and spinal cord. They are the most common type of neuron. They transmit signals from sensory neurons and other medial neurons to motor neurons and other medial neurons. Normally, they form complex circuits that help you respond to external stimuli.
For example, when you touch something hot, the sensory neurons in your fingertips send signals to nerve cells in your spinal cord. Some brain neurons transmit signals to the motor neurons in your hand, which allows you to move your hand away. Other interneurons send signals to the pain centers in your brain and you feel pain.

5. Recent Research

Although research has enhanced our understanding of neurons over the last century, there is still much we don't understand.
For example, until recently, researchers believed that neurogenesis occurred in adults in an area of the brain called the hippocampus. The hippocampus is involved in memory and learning.
But a recent Trusted Source study is questioning beliefs about hippocampal neurogenesis. After analyzing hippocampal samples from 37 donors, the researchers concluded that the adults produced relatively few new hippocampal neurons.
Although the results are yet to be confirmed, they are a significant step back. Many researchers in the field had hoped that neurogenesis could help treat diseases such as Alzheimer's and Parkinson's, which cause nerve cell damage and death.

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References: mayoclinic.org, healthline.com

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Bài viết này được viết cho người đọc tại Sài Gòn, Hà Nội, Hồ Chí Minh, Phú Quốc, Nha Trang, Hạ Long, Hải Phòng, Đà Nẵng.