Nerve cell – structure, types of neurons

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Neuron is the basic functional and anatomical unit of the nervous system. It is able to receive a signal, respond to it and pass it on using special contacts (synapses) with other neurons, effectors or receptors. Humans have 86 billion neurons and roughly 300 a billion synapses.

Structure[edit | edit source]

A nerve cell consists of a body' (soma, perikaryon) and two types of processes: afferent dendrites' and efferent neurites (axonss).

Soma[edit | edit source]

The body of the neuron is bounded by a plasma membrane, contains receptors and [ion channels]. This structure supports the creation and propagation of excitement. The neuron body contains a nucleus, Nissl substance (granular endoplasmic reticulum) and [[mitochondria].

Neuron - description

Outcrops[edit | edit source]

Dendrite[edit | edit source]

Dendrites receive input information (at the same time, it is also a trophic segment). They are mostly short, richly branched, extended into dendritic spines, which serve to modulate postsynaptic potential during its transition from synapse to dendrite. From a neurochemical point of view, they are very rich in chemically controlled ion channels. Neuron Axon wrapped in myelin

Neurites[edit | edit source]

Neurites are long projections leading impulses from the body of a neuron (to another neuron or effector), i.e. efferently. They contain ribosomes, a small amount of mitochondria and neurotubules. Neurochemically, they are rich in voltage-gated ion channels. The place where the neurite departs is the ``axon bump, which, together with the initial segment of the neurite, is the place where the action potential originates.

Myelinated neurite (= axon)[edit | edit source]

The Myelinated tract occurs along the entire length of the axon except for its beginning and terminal branching. It is important for the transmission of excitement, the stronger the axon, the faster the transmission. In the course, the myelin sheath is interrupted by Ranvier's notches, where the sections between individual notches are called internodes. The speed of conduction is directly proportional to the length of the internodes. In the PNS, the extracellular space at the site of the notch of Ranvier is separated from the surroundings by a continuous basement membrane that spans the notch area, in the CNS, the projections of astrocytes directly attach here.

Searchtool right.svg For more information see Nerve Fiber.
Unmyelinated neurite[edit | edit source]

The main function of the neurite is the transport of certain substances from the body to the telodendria, which is dependent on the developed system of neurofilaments and neurotubules. We distinguish between anterograde transport (from the cell body) and retrograde transport (into the cell body – spread of viruses and toxins).

Types of neurons
1. Unipolar
2. Bipolar
3. Multipolar
4. Pseudounipolar

Division of neurons[edit | edit source]

Neurons can be divided morphologically, according to the length of their axon, and functionally.

  1. Morphological:
    • multipolar (contain many tiny profusely branching dendrites);
    • bipolar (contains one relatively long dendrite and axon, we include sensory neurons (cutaneous, auditory, olfactory) and nociceptive fibers);
    • unipolar;
    • pseudounipolar (has a long dendrite that merges with the axon).
  2. According to axon length:
    • Golgi type I – neurons with a long neurite;
    • Golgi II. type – neurons with a short neurite.
  3. Functional:
    • principal (projection) - connect distant areas of the nervous system;
    • local (interneurons) - connect nearby areas.


Links[edit | edit source]

Related Articles[edit | edit source]

External links[edit | edit source]

References[edit | edit source]

  • yes. . Lékařská fyziologie. 4. edition. Praha : Grada Publishing, a.s., 2003. ISBN 80-247-0512-5.
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