CHAPTER 21. REGULATION OF RESPIRATION

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

Profile materials Control questions Situational tasks

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).

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.