What Is the Difference Between Axons and Dendrites?

A neuron's protrusion is an extension of the neuron's cell body. Due to its morphological structure and function, it can be divided into dendrites and axons; dendrites are one or more protrusions from the cell body, which are radial. There is only one cell body in each axon. The cytoplasmic part of the axon that emits the axon is mostly conical. It is called axon mound. There is no Nissl body, and there are mainly neurofibrils.

Dendrites and axons

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The dendrites are one or more protrusions from the cell body, which are radial. The initial part of the cell body is thicker and thinner after repeated branching, like a dendritic shape. The structure of the dendrite is similar to that of the brain body, and the cytoplasm contains

Each neuron has only one axon, and the cytoplasmic part of the axon is mostly conical, called axon mound. There is no Nissl body, and there are mainly neurofibrils. After the axons protrude from the cell body, the first segment, called the initial segment, is about 15-25 m in length, usually thinner than dendrites, uniform in thickness, smooth on the surface, less branched, and unmyelinated. After a certain distance from the cell body, the myelin sheath is engulfed, that is, the myelinated nerve fiber. The axon ends are mostly slender branches, which means that the axon has not ended, and it is in contact with other neurons or effector cells. The cell membrane on the surface of the axon is called the axon membrane, and the cytoplasm inside the axon is called the axon or axoplasm. There are many neurofibrils and slender mitochondria in the axon that are parallel to the long sleeves of the axon. However, there is no Nissl body and Golgi complex. Therefore, proteins cannot be synthesized in the axon. The renewal of axon component metabolism and neurotransmitters in synaptic vesicles are synthesized in the cell and flow to the axon end through the microtubules and nerve filaments in the axon.

Under the electron microscope, there are many longitudinally parallel nerve filaments and nerve microtubules from the axillary to the axon, as well as a continuous long longitudinal tubular smooth endoplasmic reticulum and polyvesicles. Under high-power electron microscopy, it can also be seen that there are extremely fine fiber network connections between nerve filaments and neural microtubules. Such laterally connected ultrafine fibers are called microbeams to support. There are also synaptic vesicles at the end of the axon.

The cell body and axon of the axon transport neuron are structurally and functionally integrated. Most of the neuronal metabolic activities are formed in the cell body. The overall physiological activity of the neuron is metabolized by the continuous flow of axons.

Studies have shown that neuronal cytoplasm flows from the soma to the distal axon, and from the distal axon to the soma. This kind of biaxial flow with different directions and different speeds is called axonal transport. The transport from the cell body to the distal axon is called inclined transport because the transport direction is the same as the direction of the axonal flow. This type of transport is divided into fast and slow: fast transport, whose speed is 200 to 500 mm per day, is a neuronal cell body Synthetic neurotransmitters of various vesicles and related enzymes flow through the long tubular smooth surface endoplasmic reticulum and along the surface of the microtubules to the axonal end, and are released when the nerve impulses. Slow transport is also known as axonal flow. Its speed is 1 to 4 mm per day. It is mainly a protein synthesized by the neuron soma, which continuously flows to the axon end to renew the structural proteins such as the axonal matrix, nerve filaments, and microtubules. . Reverse transport is the metabolites of the axon end and proteins, neurotrophic factors, and some small molecular substances that are taken up by the axon end through human cells. The axon end is transported to the cell body. The transport direction is opposite to the axonal flow. The speed is 1-4mm per day. This kind of transportation is mainly realized by multi-bubbles. A multivesicular body is a large vesicle containing many vesicles, which contain metabolites or neurotrophic factors, respectively. After the metabolites are reversely transported to the cell body, the role of lysosomes can decompose digestion and renewal. After the neurotrophic factors enter the cell body, they can promote the metabolism of neurons and regulate the physiological functions of neurons. Whether it is forward or reverse transportation, it is realized by ATP provided by mitochondria. When infected for some reason, some viruses or toxins are transported by the reverse and turn into the brain of the neuron to cause the disease. Axonal transport is an important manifestation of the physiological functions of various organelles in neurons.

The main function of axons is to transmit nerve impulses from the soma to other neurons or effector cells. Axon conduction The start of nerve impulses is at the initial stage of the axon, which conducts along the axon membrane.