21.1 General characteristics of external breathing regulation
21.2 Types of pulmonary respiration (in a healthy person)
21.3 Respiratory center
21.4 Role of brainstem
21.5 Functional system maintening blood gas composition, its central and peripheral components
21.6 Breath-holding functional tests
21.7 Features of breathing in different conditions
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21.1. General characteristics of external breathing regulation
Regulation of respiration is coordinating the respiratory minute volume with the metabolic needs of the body in various conditions. There are two types of such regulation: involuntary (from the respiratory center of the medulla oblongata through motor neurons of respiratory muscles) and voluntary (along the cortical-spinal pathways through motor neurons of respiratory muscles).
The main regulated indices. For pulmonary ventilation there are evolutionarily selected indices of arterial
blood and cerebrospinal fluid: O2 tension (pO2) (90- 100 mm Hg), CO2 tension (pCO2) (38-42 mm Hg), and the concentration of H+ (pH) (normal range 7.4±0.04,
or 40 nmol H+/l).
The effectiveness of regulation of pulmonary ventilation is estimated by the ratio of respiratory rate to depth of breathing in different conditions.
The main components of the regulation system include chemoreceptors, mechanoreceptors, and central and executive parts (Fig. 21.1).
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Fig. 21.1. Schematic representation of regulation of respiration. See the text for more details
The chemoreceptor component provides the respiratory center with information about the level of pulmonary ventilation required at any given moment. If the value of pO2 is reduced, and pCO2 is increased, the respiratory center receives information that the body needs a higher level of ventilation. Mechanoreceptors provide the respiratory center with information about actual ventilation of the lungs based on the change of activity in the respiratory muscles.