Classification by Localization in the Reflex Arc
This type of classification (by level of organization) is based on dividing all disorders according to which specific link of the reflex arc is damaged. Three main groups of pathologies are distinguished:
- Afferent disorders. These occur at the stage of information input. They are caused by receptor disorders (perception of primary impact) and impaired subsequent signal transmission from peripheral afferent structures directly to the nerve centers.
- Central disorders. These are associated with dysfunction of the nerve centers themselves. They manifest as impaired analysis of incoming afferent signals, as well as disruption in the synthesis and generation of the response efferent signal by central nervous system neurons.
- Efferent disorders. These are characterized by problems along the pathway from the center to the periphery. They include impaired nerve impulse conduction from 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 a nerve impulse—whether in the afferent, central, or efferent segment—inevitably affect the functioning of the entire organism.
Even localized disorders lead to significant impairment in the normal activity of physiological and functional systems. In cases of severe, deep lesions of the neural apparatus, 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 topical diagnosis, pathophysiology classifies nervous system function disorders based on three criteria. They reflect the very essence of the functional failure:
- By impairment of influence intensity. The strength of the nervous system's impact on tissues and target organs is assessed. Pathology may manifest either as a pathological weakening of such influences (stimulation deficit) or their pathological enhancement (hyperstimulation).
- By appropriateness of response. The reaction to incoming afferent signals is evaluated. The main manifestation here is the development of so-called phase states—a specific change in the reaction of structures to stimuli of varying strengths (when strong and weak stimuli elicit a distorted or paradoxical response).
- By predominantly impaired type of activity. Specific functional deficits are distinguished: neurogenic movement disorders, sensory disturbances, neurotrophic disorders (metabolic and trophic regulation) of target tissues, and higher nervous activity (HNA) disorders.