Classification of nervous system disorders

Classification by localization in the reflex arc

This type of classification (by level of organization) is based on dividing all disorders depending on which specific link of the reflex arc has been damaged. There are three main groups of pathologies:

1. Afferent disorders. They occur at the stage of information input. They are caused by receptor disorders (perception of primary impact) and impaired subsequent signal conduction from peripheral afferent structures directly to the nerve centers.
2. Central disorders. Associated with dysfunction of the nerve centers themselves. They manifest as impaired processing of incoming afferent signals, as well as malfunctions in the synthesis and generation of the response efferent signal by central nervous system neurons.
3. Efferent disorders. Characterized by problems on the pathway from the center to the periphery. They include impaired nerve impulse conduction from the centers to effector organs and impaired adequate perception of this impulse by the efferent structures themselves (target tissues).

Consequences of level-specific disorders

Any disruptions along the pathway of the nerve impulse—whether afferent, central, or efferent—inevitably affect the functioning of the entire organism.

Even local disorders lead to significant disruption of normal activity in physiological and functional systems. In cases of severe, profound damage to the nervous apparatus, a complete disintegration of these systems occurs, making it impossible to maintain adequate vital activity and adaptation.

Typical forms of pathology by the nature of disorders

In addition to topographic diagnosis, pathophysiology classifies nervous system function disorders based on three criteria. They reflect the very essence of the functional failure:

• By the abnormality of influence intensity. The strength of the nervous system's impact on target tissues and organs is evaluated. Pathology can manifest either as a pathological decrease in such influences (stimulation deficit) or their pathological increase (hyperstimulation).
• By response adequacy. The reaction to incoming afferent signals is evaluated. The main manifestation here is the development of so-called phase states—a specific alteration in the reaction of structures to stimuli of varying strength (when strong and weak stimuli elicit a perverted or paradoxical response).
• By the predominantly impaired type of activity. Specific functional deficits are distinguished: neurogenic movement disorders, sensory disorders, neurotrophic disorders (metabolic and regulatory nutrition of target tissues), as well as higher nervous activity (HNA) disorders.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Mechanisms of development of nervous system phase states
• Pathophysiology of neurogenic movement disorders
• Higher nervous activity (HNA) disorders
• Neurotrophic disorders of target tissues
• Mechanisms of impaired afferent signal analysis in the CNS

Other topics in "Chapter 28. Standard forms of pathology of the nervous system"

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