How Is Respiration Regulated in Humans?

Reflex

Breathing, or respiration, is reflexive in humans. The reflex is normally automatic, meaning that it happens without being controlled. However, it can be overridden and be controlled when necessary. This gives humans the ability to hold their breath or change their breathing rates. The automated breathing is controlled by the brain, based on the body's need for oxygen and the amount of air that is provided at the time in the atmosphere.

Breathing

The brain is the primary control for respiration. It receives information from the lungs as well as cells telling how much air is needed to do whatever action the body is doing at the time. The brain signals the body to breathe, based on this information, at the rate needed to pull in the required oxygen and expel carbon dioxide. Inhalation is active, with muscles being used to expand and fill the lungs. The exhale is passive in that muscles are not generally used to force the air out. The expansion of the lungs stretches them out, and an exhale is mainly the lungs just moving back into their normal state much like a balloon that deflates. However, with heavy exercise or controlled breathing, muscles are sometimes used by the body to regulate the breathing.

Carbon Dioxide

A need for oxygen is not the only variable controlling air flow. A build up of gases in the body can also signal the brain to breathe. Carbon dioxide is a gas that the body creates as a by-product of taking in oxygen, and it cannot stay. When levels of the gas reach a certain point in the blood, neurons signal the brain to breathe to exchange the gas for oxygen. The exhalation is the removal of the carbon dioxide

Other Helpers

A safety feature in the reflex of breathing is the hering-breuer reflex. This reflex stops inhalation and keeps the lungs from expanding too much. Also, the spinal cord reflex controls muscles that help with gasping and increased need for air, such as when a person is exercising.

References

• Breathing Coordination
• Regulation of Respiration
• Control of ventilation