Respiration and Gas Transport

Respiration is the biological process by which organisms exchange gases with their environment. Oxygen is the central gas involved in this process - organisms take in oxygen and release carbon dioxide. Among the options: mouth is just an entry point for air, circulation is the transport system, carbon monoxide is actually toxic to respiration, while oxygen is the essential gas that drives cellular respiration.

During inhalation, humans take in oxygen which is essential for cellular respiration. This oxygen binds to hemoglobin in red blood cells and is transported throughout the body to produce energy.

Despite accounting for a very small fraction of total body weight, the metabolic activity of the brain is immense. It consumes about 20 percent of the body's resting oxygen and glucose calories.

Although the brain represents only about 2% of body weight, it receives approximately 20% of the body's blood supply and consumes about 20% of oxygen intake. This disproportionate allocation reflects the brain's high metabolic demands and constant need for oxygen and nutrients to function properly.

Carbon monoxide (CO) is produced by incomplete combustion in automobile engines. CO binds to hemoglobin in red blood cells about 200 times more strongly than oxygen, preventing oxygen transport and causing hypoxia, which is especially dangerous for people with heart or lung conditions.

During respiration, humans inhale oxygen from air which is used for cellular respiration. Carbon dioxide is exhaled as a waste product, not carbon.

Yawning is an involuntary physiological response that occurs when oxygen levels in the brain drop and carbon dioxide levels rise. The deep inhalation during a yawn increases oxygen intake while the exhalation helps expel more carbon dioxide, helping restore proper gas balance in the blood and brain. Eating, drinking water, or running do not directly address this specific physiological need for gas exchange in the brain.

CO causes hypoxia because it has 200-250 times higher affinity for hemoglobin than oxygen, forming carboxyhemoglobin and preventing oxygen transport. Options A, C, and D are incorrect because CO is not converted to CO2, does not destroy hemoglobin structure, and primarily affects oxygen transport at the molecular level rather than the respiratory center in the brain.

The human brain consumes about 20% of the body's oxygen despite being only 2% of body weight. This high metabolic rate supports continuous neural processing. The 40% and 15% figures are commonly cited but incorrect.

The brain consumes about 20% of the body's oxygen supply despite representing only about 2% of body weight. This high oxygen demand reflects the brain's intense metabolic activity as it constantly processes information.

This is the correct option. In exhaled air, the percentage of carbon dioxide is 4.4%.

Oxygenation of blood occurs in lungs

A condition in which an extreme decrease in the concentration of oxygen in the body accompanied by an increase in the concentration of carbon dioxide leads to loss of consciousness or death. Asphyxia can be induced by choking, drowning, electric shock, injury, or the inhalation of toxic gases.

Capnography is a noninvasive procedure. It is used to measure exhaled carbon dioxide concentrations of client receiving mechanical ventilation. Capnography requires continuous sampling of exhaled air. The test is noninvasive and painless. Client who require capnography already have an endotracheal tube or tracheostomy tube in place for mechanical ventilation or airway management. A sensor is attached to the endotracheal tube or tracheostomy tube to measure end tidal carbon dioxide.