Respiratory physiology

The role of respiration in heat dissipation mechanisms

During vital activity, the body needs to constantly dissipate excess heat into the external environment. This process is provided by physical thermoregulation, which combines both purely physical phenomena and complex physiological reactions.

One of the most important physiological mechanisms is the intensity of external respiration. Heat loss through the lungs occurs due to the constant evaporation of moisture from the surface of the respiratory tract. This process works in a single system with other heat release mechanisms.

Additionally, the body loses heat with excreta. It is important to note that heat loss with feces (defecation) and urine (urination) accounts for exactly 1% of the total heat dissipation volume.

Respiration during intense physical activity

Any intense muscular work requires a global restructuring of autonomic functions. During this period, pulmonary ventilation increases sharply, occurring in parallel with an increase in stroke volume, cardiac output, and coronary blood flow.

A key role in stimulating the respiratory system is played by humoral regulation. In response to exercise, hormones and biologically active substances (BAS) are released into the blood:

• Adrenaline and noradrenaline.
• Vasopressin and angiotensin.
• Bradykinin and cholecystokinin.

These substances alter the intensity of cellular metabolism. Their effects manifest as increased cardiac activity, digestive tract motility, and most importantly, a powerful enhancement of both external and tissue respiration.

Preparation of the respiratory and muscular apparatus begins even in the pre-work state. Nerve impulses from the cerebral cortex and brainstem activate cells of the sympathetic division of the ANS (localized in the lateral horns of the thoracic spinal cord segments). This causes a fourfold increase in muscle blood flow. During the performance of the work itself, local metabolic regulatory mechanisms begin to play the leading role.

The link between respiration and the self-regulation of cognitive activity

The respiratory system participates not only in metabolic processes, but also in higher cognitive functions. System quanta of cognitive activity consist of external and internal links of self-regulation.

The internal link determines the processes of inner speech. It is formed on the basis of memory mechanisms and the manipulation of the informational integral—the so-called internal "Self". The results of such inner speech are:

1. Semantic concepts (reflecting real objects and the relationships between them).
2. Key words.
3. Results of mathematical operations.

Physiologically, these processes are accompanied by micro-changes in the activity of oral and vocal muscles, somatoautonomic reactions, and specific changes in respiration.

The leading mechanism for organizing this process is feedback (afferentation). Signals enter the central nervous system via two channels:

• From the vocal cords and muscles (including respiratory ones) that physiologically support inner speech.
• From special brain structures responsible for the semantic and emotional evaluation of the obtained mental result.

Class and exam questions

What else to study on this topic

• Mechanisms of feedback from brain structures during emotional evaluation
• The role of the sympathetic division of the ANS in thoracic segments during the pre-work state
• Local metabolic regulatory mechanisms in a working muscle
• Formation of semantic concepts and manipulation of the internal "Self"
• The effect of BAS on digestive tract motility during exercise

Other topics in the "Thermoregulation" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.