What determines the respiratory rhythm in body?

The respiratory rhythm in the body is determined by a complex interaction of several factors, including:

1. Central Respiratory Pattern Generators:

The primary control of respiratory rhythm is exerted by specialized groups of neurons within the brainstem, known as the central respiratory pattern generators (CRPGs). These neurons are located in the medulla oblongata and the pons. The CRPGs generate and coordinate the basic rhythm of breathing.

2. Chemoreceptors:

Chemoreceptors are sensory receptors that are sensitive to changes in the chemical composition of the blood and cerebrospinal fluid. There are two types of chemoreceptors involved in respiratory control:

a. Peripheral Chemoreceptors:

Peripheral chemoreceptors are located in the carotid bodies, which are small clusters of cells situated near the carotid arteries in the neck, and the aortic bodies, which are located near the aortic arch in the chest. These chemoreceptors sense changes in the partial pressure of oxygen (PaO2), partial pressure of carbon dioxide (PaCO2), and pH of the blood. When PaO2 decreases, PaCO2 increases, or pH drops, the peripheral chemoreceptors send signals to the respiratory centers in the brainstem, leading to an increase in respiratory rate and depth.

b. Central Chemoreceptors:

Central chemoreceptors are located in the medulla oblongata, near the CRPGs. They respond primarily to changes in PaCO2 and pH of the cerebrospinal fluid. When PaCO2 increases or pH decreases, the central chemoreceptors stimulate the respiratory centers, resulting in increased respiratory activity.

3. Mechanoreceptors:

Pulmonary stretch receptors are mechanoreceptors located in the airways and lung tissues. They sense changes in lung volume and airway resistance. When the lungs are inflated during inhalation, the stretch receptors send signals to the brainstem, inhibiting the respiratory centers and leading to exhalation. This reflex is known as the Hering-Breuer reflex.

4. Higher Brain Centers:

Higher brain centers, including the cerebral cortex and limbic system, can also influence the respiratory rhythm. Voluntary control of breathing, such as holding one's breath or taking a deep sigh, is mediated through these higher brain regions. Emotions and stress can also affect respiratory patterns.

The respiratory rhythm is a dynamic process that results from the integration of signals from chemoreceptors, mechanoreceptors, and higher brain centers, under the control of the central respiratory pattern generators. This complex interplay ensures that the body maintains appropriate ventilation to meet the metabolic demands and oxygen supply to tissues while eliminating carbon dioxide.