Parts of the neuron
It originates from the ectoderm and its main components are cells, surrounded by scarce intercellular material. The cells are of two different classes: neurons or nerve cells and neuroglia or supporting cells. (Fig 1).
The central nervous system (CNS) originates from the epithelium of the neural tube and its nervous tissue contains neurons, neuroglia cells and blood capillaries that form the blood-brain barrier. (Fig 2)
The peripheral nervous system (PNS), which connects sensory receptors to the CNS and the CNS to effector cells, develops from the neural crest and its cells are associated with other tissues of the organism. However, it is an extension of the nervous tissue of the CNS since areas of the sensory and effector neurons and all interneurons are found in the CNS, whereas the nerve ganglia and peripheral nerves correspond to the PNS’s own nervous tissue (Fig 3).
q specialized cell junctions called synapses, located at sites of close vicinity between the terminal boutons of axon branches and the surface of other neurons (Fig 4 and 5).
The nervous system also includes non-neuronal cells, called glial cells. Glial cells perform many important functions that keep the nervous system functioning properly. For example, glial cells:
The brain is composed of many networks of communicating neurons and glials. These networks allow different parts of the brain to “talk” to each other and work together to control bodily functions, emotions, thinking, behavior and other activities.1,2,3
Types of neurons
The synapse occurs at the moment when presynaptic and postsynaptic chemical-electrical activity is registered. If this condition is not present, there is no synapse. In this action, chemically based ionized neurotransmitters are released, whose charge cancellation causes the activation of specific receptors that, in turn, generate other types of chemical-electrical responses.
Synapses allow the neurons of the central nervous system to form a network of neural circuits. They are crucial for the biological processes underlying perception and thought. They are also the system by which the nervous system connects and controls all body systems.
These synapses are asymmetric in both structure and function. Only the presynaptic neuron secretes neurotransmitters, which bind to transmembrane receptors that the postsynaptic cell has in the cleft. The presynaptic nerve terminal (also called synaptic button or button) normally emerges from the end of an axon, while the postsynaptic area usually corresponds to a dendrite, cell body or other cellular areas. The area of the synapse where the neurotransmitter is released is called the active zone. In active zones, the membranes of the two adjacent cells are tightly bound by cell adhesion proteins. Just behind the membrane of the postsynaptic cell is a complex of intertwined proteins called the postsynaptic density. The proteins of the postsynaptic density serve numerous functions, ranging from the anchoring and movement of neurotransmitter receptors on the plasma membrane to the anchoring of various proteins that regulate the activity of these receptors.
The nervous system, as is known, is made up of neurons. These special cells are capable of receiving, storing and processing information; they are responsible for the body’s communication with the outside world and for the functioning of all the body’s systems. Memory, attention, thinking, imagination, creativity… are the result of the work of neurons. Thus, all these different activities could not take place without such an important element as the synapse in a neuron. To a certain extent, it is the synapses, and not the neurons themselves, that form the basis of the nervous system.
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