Afferent Synthesis and Decision-Making
The foundation of the respiratory functional system is the activity of inspiratory neurons located at various levels of the nervous system. These cells act as a powerful integrator: they continuously collect and process incoming information (afferentation) to form a complete act of inspiration.
For the system to function correctly, it relies on several key sources of information:
- Chemoreceptors: These are the primary informants of the system, evaluating blood gas composition and transmitting baseline signals regarding the body's current respiratory demand.
- Somatic and Visceral Signals: Inspiratory neurons receive data on body temperature, alveolar stretch, and impulses from skeletal and respiratory muscles.
- Higher Nervous Activity and Emotions: Inspiration parameters are significantly influenced by pain, emotional bursts, and the specifics of human social activity (e.g., when respiratory coordination is required for lecturing, singing, or regular speech).
Based on the entire complex of collected data, inspiratory neurons trigger a complex cascade of molecular processes. The result is a physiological "decision" regarding the exact volume of air required by the body at that second. This decision is instantly converted into a series of nerve impulses sent to the respiratory muscles, initiating mechanical movement.
Action Acceptor and Automatisms of the Respiratory Act
A crucial link in the respiratory functional system is the apparatus for evaluating the achieved result — the action acceptor. Its main task is to continuously compare what the body needs with what it actually receives.
This mechanism constantly compares the calculated respiratory demand with the quantity and quality of air that has actually entered the lungs as a result of inspiration. Information is transmitted via specific neural and humoral codes.
Under normal physiological conditions, this evaluation and correction process occurs completely unconsciously. The respiratory act is strictly automated, and a person does not think about how often or how deeply they breathe. However, the situation changes cardinally in the event of a mismatch. If the volume or gas composition of the incoming air does not match the body's actual demands, automatism becomes insufficient. At this moment, a critical physiological shift occurs: consciousness mechanisms are recruited into respiratory regulation, and specialized behavior is formed.
Behavioral Self-Regulation Under Extreme Conditions
The behavioral link of the respiratory functional system is activated predominantly in extreme situations. This occurs when internal automatic self-regulation mechanisms are no longer sufficient to cover the arisen respiratory demand.
A classic example of a behavioral response can be observed when a person is in a confined, poorly ventilated room with a large crowd of people. The chain of reactions looks as follows:
- Environmental Change: The concentration of $O_2$ in the surrounding and inhaled air critically decreases while the level of $CO_2$ simultaneously rises.
- Sensory Reaction: The body automatically detects these changes, which manifests at the psychological level as strong emotional discomfort.
- Motivation Formation: Against the background of mounting discomfort, the person develops a powerful respiratory motivation — an irresistible desire to eliminate the impact of the extreme situation or escape it (e.g., immediately leaving the stuffy room).
- Action Implementation: Relying on the formed motivation, the person performs targeted behavioral acts that ultimately lead to the restoration of normal gas exchange.
Systemic Compensatory Mechanisms
The main principle of the system's operation under pathology or stress is that any compensatory readjustments are aimed at obtaining a useful adaptive result. Regardless of where the disturbance occurred, the ultimate goal of the system is to maintain normal $O_2$ and $CO_2$ blood levels.
According to research by P.K. Anokhin and E.L. Golubeva, removal of one lung (pneumonectomy) triggers a large-scale systemic reaction. The compensatory load falls not only on the remaining intact lung, as one might assume. The process of actively maintaining gas homeostasis urgently involves:
- The heart and vascular bed.
- The blood system (altering the oxygen-binding capacity of hemoglobin).
- Excretory organs, which correct the acid-base balance.
In addition to anatomical defects, individual regulatory adjustments can be provoked by external behavioral factors. This refers to work requiring prolonged maintenance of an awkward posture, performing monotonous operations, or manipulating very small parts. The etiology of such changes often lies in emotional overstrain and chronic stress, affecting both external and internal self-regulation links. Understanding these mechanisms is of immense clinical significance and is invariably taken into account by specialists when diagnosing the health status of professional athletes and industrial workers.