How many neurons does the brain have?

Neurons are important tissues in the human body and play a decisive role in various functions of the human body. The brain is an important part of the human body, and its structure is also composed of neurons. And once these neurons become diseased, the impact on patients is immeasurable. So, how many neurons are there in the brain? The following is a detailed introduction to the relevant knowledge of neurons.

1. What is a neuron?

Neuron (neuron, neure), the basic structural and functional unit of the nervous system. The main parts include dendrites, cell body, axon and cell membrane. Dendrites are shaped like branches with many branches and have many branch-like processes, so they have the potential to receive input from many other cells. The cell body contains the nucleus, and most of the organelles that maintain cell life are also inside it. The axon is the output end of the cell, extending from the cell body and is generally very long. Many axons are wrapped in myelin, which serves to insulate them from the flow of information from other cells. There are many gaps along the sheath wall, called Ranvier nodes. The axon ends at the synaptic terminal.

How many neurons are there in the brain?

In fact, humans and baboon brains have the same number of neurons: 86 billion, according to Brazilian neuroscientist Suzana Herculano-Hölzer. With the help of her colleagues, she processed the four brains into "brain soup" in a rather horrifying way, then counted the number of neuron nuclei to determine the true number of neurons in the human brain. The brains belonged to four adult men aged 50, 51, 54 and 71, who donated their brains for scientific research. None of them had neurological diseases.

3. The main functions of neurons

Neurons are the structural and functional units of the nervous system. Neurons have diverse morphologies and functions, but structurally they can be roughly divided into two parts: the cell body and processes. Processes are divided into axons and dendrites. Dendrites are generally short and thick, with many branches; axons are often very long, branching out from the axon hillock of the cell, with uniform diameter. The first segment is called the initial segment, and it begins to acquire myelin and become a nerve fiber after leaving the cell body for a certain distance. It is customary to divide nerve fibers into two types: myelinated fibers and unmyelinated fibers. In fact, the so-called unmyelinated fibers also have a thin layer of myelin sheath, and are not completely unmyelinated.

Neurons have the function of receiving, integrating and transmitting information. Generally speaking, for neurons with long axons, dendrites and cell bodies receive and integrate information from other neurons, and then transmit the information to other neurons or effectors through the axons.

According to their function, neurons can be divided into three types: afferent neurons (sensory neurons), interneurons (communication neurons) and efferent neurons (motor neurons). If classified according to their influence on subsequent neurons, they can be divided into excitatory neurons and inhibitory neurons.