What causes breath to be taken?

Breathing is primarily controlled by the respiratory centre, a group of neurons located in the brainstem. The respiratory centre sends signals to the diaphragm and the intercostal muscles, which are responsible for the movement of the lungs and the inhalation of air.

The respiratory centre is influenced by several factors, including:

- Chemical factors: Blood levels of carbon dioxide and oxygen:

- Increased carbon dioxide levels (hypocapnia) stimulate breathing, while low levels (hypercapnia) depress it.

- Decreased oxygen levels (hypoxemia) also stimulate breathing.

- Lung receptors: Specialized receptors in the lungs, such as stretch receptors and chemoreceptors, provide feedback to the respiratory centre about lung inflation, airway resistance, and blood oxygen levels.

- Higher brain centres: The respiratory centre can be influenced by voluntary control from higher brain centres, allowing for conscious control of breathing.

- Reflexes: Certain reflexes, such as the diving reflex and the gag reflex, can modify the respiratory pattern temporarily.

- Emotional factors: Emotions such as fear, anxiety, and joy can influence the rate and depth of breathing.

- Exercise: Physical activity increases the demand for oxygen and carbon dioxide production, leading to increased respiratory rate and depth.

- Sleep: During sleep, the respiratory rate and depth generally decrease.

In summary, the control of breathing involves the interplay between the respiratory centre in the brainstem, chemical factors in the blood, signals from lung receptors, higher brain centres, reflexes, emotional influences, and physiological demands such as exercise and sleep.