Breathing: physiology, regulation, delay possibilities
Here we will speak in the external respiration of a person – those very inhales and exhales that we all do, and which can be in the zone of our attention and certain control. How do we breathe, and what follows from this?
Phases of inhalation and exhalation
Breathing is known to be a reflex automatic process regulated by the central nervous system. During the inspiratory phase, contraction occurs:
- the diaphragm, which bends downward, puts pressure on the organs in the abdominal cavity, thereby increasing the volume of the sternum;
- the intercostal muscles, due to which the ribs move apart, and the chest cavity expands further.
When inhalation is carried out under standard natural conditions, at this phase the intra-alveolar pressure is approximately 3 millimeters of r.s. below atmospheric pressure, and, due to this discrepancy, air is freely directed into the respiratory tract, and the system itself finds equilibrium.
As for exhalation, this is already a reverse process, accompanied by an increase in intra-alveolar air and, accordingly, the withdrawal of exhaust air outside.
Two groups of cells of the central nervous system are responsible for regulating the automatism of respiration – the respiratory centers located:
- in the posterior part of the brain, or rather, in its bulbar zone;
- in the varoli bridge.
The bulbar center also has its own division into inspiratory and expiratory, which, respectively, are responsible for the implementation of inhalation or exhalation. Both of these centers are affected by chemical impulses associated with the concentration of carbon dioxide in the blood. It is here that the rhythm of breathing is established, and it is not surprising that this center, being sensitive to an increase in the amount of carbon dioxide, immediately responds by accelerating breathing.
As for the pons of varoli, it is possible to find apneustic and pneumotaxic centers in it, which are especially important in case of conscious cessation of breathing. The first of them is a kind of starting point of the inhalation impulse, and in the second, inhibitory signals are formed that balance the system.
The main function of this entire system is to maintain the content of carbon dioxide and oxygen at a level sufficient to ensure vital activity, and if the partial pressure of these vital gases changes during the regulation of respiration, this affects both the frequency and depth of respiration and the state of the body in the whole.
Of course, it is the concentration of carbon dioxide that affects the respiratory process more, since any change in it is immediately followed by the reaction of the respiratory centers. Bulbar receptors are stimulated, then one or both centers of the pons are stimulated, and they are already giving an impulse to one of the bulbar centers. Holding the breath can even be beneficial for the body, but exactly until the increase in carbon dioxide in the blood results in pronounced contractions of the diaphragm muscles. This means that the breath hold limit has been reached.