Key characteristics of external inhibition
Unconditioned inhibition is a basic protective and adaptive reaction of the organism. Its main distinctive feature is that it arises suddenly. No prior experience or acquisition of special skills is required to trigger it—it is a genetically determined, innate property of our nervous system.
Most commonly, this type of inhibition is clearly manifested when the organism finds itself in a new, unfamiliar environment. Any environmental factor characterized by novelty or high intensity is capable of instantly interrupting the conditioned reflex activity that was being carried out before its appearance.
Mechanism of development according to I.P. Pavlov
Academician I.P. Pavlov detailed the sequence of events leading to the development of external inhibition. This process can be divided into several logical stages:
- The impact of a novel stimulus immediately triggers orienting-exploratory activity. Pavlov aptly named this reaction the "What is it?" reflex.
- As a result, a new focus of excitation is formed in the central nervous system. Now, two competing foci exist simultaneously in the CNS: one associated with the current conditioned reflex, and the other with the new orienting reaction.
- The excitation generated by the "What is it?" reflex turns out to be significantly stronger.
- According to the principles of nervous system function, a stronger focus of excitation actively "inhibits" (suppresses) a weaker one. Thus, the execution of the current conditioned reflex is temporarily or completely halted.
Systems approach and localization
Examining the process from the standpoint of the theory of functional systems, the essence of unconditioned inhibition reduces to competition between systems. The stronger functional system, aimed at analyzing the novel stimulus and ensuring safety, suppresses the weaker functional system responsible for routine current activity.
A critically important aspect for understanding this type of inhibition is its localization. The physiological cause that halts activity is always located outside the arc of the conditioned reflex undergoing inhibition. For this reason, this type of inhibition is traditionally called external.
Briefly: answers to topical questions
What types of unconditioned inhibition are distinguished in physiology besides external inhibition?
In addition to external unconditioned inhibition, sources describe protective inhibition associated with transmessional/peassimal inhibition.
- Protective inhibition arises under the influence of an excessively strong stimulus.
- Its mechanism: the strength of the stimulus exceeds the optimum of functional lability of nerve cells, and neurons transition into a state of pessimum (transmarginal inhibition).
- Biological significance: protection of nerve cells from exhaustion and the damaging action of super-strong stimuli.
What is the complete biological role (significance) of unconditioned inhibition for the organism?
Sources directly indicate the biological significance of protective inhibition: it protects nerve cells from exhaustion and the damaging action of ultra-strong stimuli.
The clinical significance of protective inhibition is also noted: it accompanies a number of mental disorders, manifests in stuporous states and shock, and underlies physiological sleep.
What properties of the nervous system determine the capacity for unconditioned inhibition?
Sources classify strength, balance, and mobility as the main properties of nervous processes (excitation and inhibition).
- Strength characterizes the performance limit beyond which pessimal inhibition sets in.
- Balance reflects the ability to transition from the process of excitation to inhibition and vice versa.
- Mobility is designated as one of the three main properties of nervous processes.
To easily remember the essence of unconditioned inhibition, use the rule "The strong defeats the weak, and the new defeats the old." As soon as the "What is it?" signal sounds, all old tasks are canceled.
Class and exam questions
Is training required for unconditioned inhibition to occur?
No, it is not required. This is an entirely innate property of the central nervous system that is ready to function from birth.
What is the "What is it?" reflex?
This is an orienting-exploratory reaction of the organism to any novel or strong stimulus, first described by I.P. Pavlov.
Where is the cause of external inhibition localized?
The cause (focus of stronger excitation) is always located outside the reflex arc of the conditioned reflex being inhibited.
What else to study on this topic
- Detailed analysis of orienting-exploratory activity
- Interaction of excitation foci in the CNS: principles of dominance
- The concept of the functional system and its role in inhibition
- Differences between external inhibition and internal (conditioned) inhibition
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