Receipt of pathogenic agents in the nervous system

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There are two basic ways of pathogens entering the CNS - from the blood (through the vascular wall), and the nerve trunks.

In the first case, the pathogenic agent (toxic agent, viruses, and other microbes.) Must overcome the blood-brain barrier (BBB), which is formed of the vascular wall (endothelial cells) and glial elements (astrocytes). BBB provides active and selective transport from the blood into the brain of nutrients and other biologically active substances required for the activity of the brain. At the same time it protects the brain from the direct action of pathogenic agents found in the blood. In fetuses and newborns go through the BBB more. Some toxic agents (strychnine, alcohols, some pharmacological agents) are relatively well BBB. For biological pathogens (viruses, bacteria) in the normal blood-brain barrier is almost impermeable. However, in pathological conditions by the action of a number of physical and chemical factors enhanced the permeability of the BBB that weigh down the disease process. Thus, a strong prolonged stress contributes to the entry of influenza virus into the brain.

Ways of receipt of a number of pathogenic agents in the central nervous system are nerve trunks. Neural pathway characteristic of tetanus toxin, polio virus, rabies and others. The input gate for the tetanus toxin is mionevralny synapse, where

toxin acts on the motor fibers in the spinal cord and the medulla oblongata. In the CNS, the toxins (tetanus), viruses, antibodies to nerve tissue can spread from neuron to neuron in neural processes (with axo- flow) and interneuronal spaces.