Chapter 28. Typical Pathological Forms of the Nervous System
11 topics with brief reviews: definitions, key facts, and class questions.
This chapter is dedicated to the fundamental mechanisms underlying nervous system dysfunction. Here, we analyze the pathogenesis from the cellular level (neuronal injury and the neurodystrophic process) to systemic dysfunctions. You will study the classification of disorders, the concept of pathological hyperactivation of the nervous system, and the mechanisms of neurosis development.
Special attention is paid to the motor and sensory systems. The section details disorders of efferent innervation: central paralysis and paresis, extrapyramidal disorders, and ataxia. Separate subsections cover sensory disorders and the pathophysiology of pain—a complex phenomenon that frequently transforms from a protective mechanism into a disease itself.
In classes and exams, the differential diagnosis of paralysis, the mechanisms underlying the formation of a generator of pathologically enhanced excitation, and the pathogenesis of the neurodystrophic process are evaluated most rigorously. Mastery of these topics is not only the key to successfully passing pathophysiology, but also a bedrock foundation for future clinical practice.
Due to ion channel malfunction, the neuron loses potassium while accumulating sodium. According to the laws of osmosis, water follows sodium into the cell, causing hyperhydration and swelling.
What is the basis for the classification of disorders by level of organization?
It is based on the separation of disorders depending on the damaged link of the reflex arc: afferent, central, or efferent.
What does the degree of motor recovery in paralysis depend on?
On two main factors: the true size of the organic lesion focus in the nervous tissue and the degree of protective inhibition of adjacent undamaged neurons.
What is denervation syndrome?
It is a complex of metabolic, neurotransmitter, and structural-functional changes in tissues that occurs due to a decrease or complete loss of neural control over them.
What is the difference between muscular hypertonia in central and extrapyramidal paresis?
In central paralysis, tone increases unevenly (predominantly in the flexors of the arm and extensors of the leg). In extrapyramidal damage, tone increases simultaneously in both flexors and extensors, causing the "lead-pipe rigidity" effect.
What is the main difference between extrapyramidal paralysis and central (pyramidal) paralysis?
In extrapyramidal lesions, pathological reflexes and marked hyperreflexia are absent. In addition, muscle tone increases evenly in all muscle groups of a rigid type.
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