What Is a Nerve Cell?

[shén jng xì bo]

A nerve cell is a true endocrine cell. The nervous system has a large number

Cells of the nervous system, mainly including neurons and

Neuron is a highly differentiated cell, which is one of the basic structural and functional units of the nervous system. It has the function of feeling stimuli and transmitting excitement.

Neurons are the structural and functional units of the nervous system of higher animals. The nervous system contains a large number of neurons, and it is estimated that humans

Functions of neurons: The basic function of neurons is to exchange information by receiving, integrating, transmitting, and outputting information

Neurons are the main component of the brain. The neuron group realizes the analysis function of the brain through the information exchange of each neuron, and then realizes

Nerve fibers can play two roles in the tissues that they control: on the one hand, they release special neurotransmitters when the presynaptic membrane is reached by means of excitatory impulse conduction, and then act on the postsynaptic membrane, thereby changing the domination The functional activities of tissues. This effect is called functional effects. On the other hand, nerves can often release certain substances through the ends to continuously adjust the intrinsic metabolic activity of the dominated tissues.

Neurons have a high degree of differentiation, so once a neuron is injured, repair is very slow. If the injury is severe, it may cause irreparable damage, and the effect of the drug that repairs the neuron is not ideal. So, once there is damage, the consequences are serious.

Neurons: slice 40, slice 4, etc.

Under low magnification, some large blue-stained cells with protrusions-motor nerve cells in the ventral horn of the spinal cord can be seen. These nerve cells have many protrusions, but due to the slice relationship, only a few of them can be seen. There are lumps or granular substances with dark blue-purple color in the cytoplasm.

There are also a large number (tens of times as many neurons) of neurons in the nervous system, such as those in the central nervous system.

There are several classifications of neurons.

According to the number of protrusions

Neurons can be divided into three types according to the number of protrusions:

Multipolar neuron, which has one axon and multiple dendrites;

Bipolar neuron has two protrusions, one is a dendrite and the other is an axon;

Pseudounipolar neuron, a process emanating from the cell body, which is not far from the cell body and has a "T" shape. It is divided into two branches, one of which is an organ distributed to other tissues in the periphery. ; The other branch into the central nervous system, called the central process (central process). According to the direction of nerve impulses, these two branches of pseudounipolar neurons are axons and peripheral processes are dendrites; however, the peripheral processes are thin and long, similar to the axons, so they are often called axons.

According to the length of the axon

According to the length of axons, neurons can be divided into:

Cell and molecular biology of neuronal synaptic transmission

Large neurons with long axons are called Golgi type neurons, and the longest axons are more than 1m;

The small neurons of short axons are called Golgi type II neurons, and the axons are only a few microns short.

According to the function of the neuron

Divided according to the function of the neuron:

Sensory neurons, or afferent neurons, are mostly pseudounipolar neurons. The cell body is mainly located in the cerebrospinal ganglia, and the peripheral processes are located on the skin and muscles, and receive stimulation. To pass the stimulus to the center.

Motor neurons, or efferent neurons, are mostly multipolar neurons. The cell body is mainly located in the brain, spinal cord, and vegetative ganglia. It transmits nerve impulses to muscles or glands, producing effect.

Interneuron (interneuron), which is between the first two types of neurons, mostly multipolar neurons. The more animals evolve, the more intermediate neurons are. The intermediate neurons in the human nervous system account for about 99% of the total number of neurons, forming a complex network within the central nervous system.

Neurotransmitters released by neurons

According to the neurotransmitter or neuromodulator released by the neuron, it can also be divided into:

Cholinergic neuron;

aminergic neuron;

peptidergic neuron;

Amino acid energy neurons.