öndunar

Öndunar is the physiological process by which living organisms exchange gases with the environment, supplying oxygen to tissues and removing carbon dioxide produced by metabolism. In humans and other vertebrates, breathing supports cellular respiration and energy production.

In humans, breathing is driven by the diaphragm and intercostal muscles. During inhalation, the diaphragm contracts and expands the chest cavity, creating negative pressure that draws air into the lungs. Exhalation follows as the muscles relax, pushing air out. Gas exchange occurs in the alveoli, where oxygen passes into the bloodstream and carbon dioxide is released to be exhaled.

Breathing is regulated primarily by the brainstem’s respiratory centers, which respond to chemical signals from chemoreceptors that monitor blood levels of CO2, O2, and pH. While its rhythm is automatic, voluntary control from the cerebral cortex allows breath-holding, speaking, and singing. Stress, activity, illness, and environment can alter rate and depth of breathing.

Normal resting breathing for adults is about 12 to 20 breaths per minute, though rates vary by age and condition. Patterns such as tachypnea (rapid breathing), bradypnea (slow breathing), and apnea (temporary cessation) may indicate health issues and require assessment. Deep, slow breathing is often used in relaxation and certain therapies.

Breathing is central to medicine, sport, and daily life. Respiratory diseases such as asthma, chronic obstructive pulmonary disease, and infections can impair function and may require medications, oxygen therapy, or ventilation. Breathing techniques and rehabilitation aim to improve efficiency, control, and overall respiratory health. In Icelandic usage, the concept corresponds to the term öndunar, with öndun as the common noun for breathing.