Anatomy and Physiology

4 Types of Breathing

Breathing Mechanisms

Q: What mechanisms are involved in breathing?

• Movements of the diaphragm and rib cage change air pressure in the chest cavity during inhalation and exhalation.

4 Steps of Respiration in Humans

1. Breathing- This involves the inspiration of air into the lungs.
2. External Respiration- This is the diffusion of O₂ and CO₂ between air and blood in the alveoli.
3. Internal Respiration- When the blood gives O₂ to the cells and receives CO₂ to be carried away. (We will revisit in our study of circulation.)
4. Cellular Respiration- The mitochondria in cells use oxygen to break down sugar to produce water, ATP, energy and CO₂ .

Inhalation

• The lungs are sealed in two sacs, called pleural membranes, inside the chest cavity.

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• At the bottom of the chest cavity is a large dome-shaped muscle known as the diaphragm.

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Inhalation

• When you inhale, the diaphragm contracts and flattens. Muscles between the ribs also contract, raising the rib cage.

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• These actions increase the volume of the chest cavity and create a partial vacuum inside the cavity.

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• Atmospheric pressure fills the lungs as air rushes into the breathing passages.

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Exhalation

• During exhalation, both the rib cage and the diaphragm relax, decreasing the volume of the chest cavity and making air pressure in the chest cavity greater than atmospheric pressure.

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• Air rushes back out of the lungs.

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Exhalation

• Exhalation is usually a passive process, but to blow out a candle, speak, sing, or yell, you need more force than passive exhalation provides.

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• The extra force is provided by muscles between the ribs and abdominal muscles, which contract vigorously as the diaphragm relaxes.
• Breathing works only because the chest cavity is sealed.

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• If a wound punctures the chest—even if it does not affect the lungs directly—air may leak into the chest cavity and make breathing impossible. This is one reason chest wounds are always serious.

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Control of Breathing

• Breathing is controlled by the medulla oblongata (brain stem); it is an involuntary process.

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• When CO₂ levels get too high, the medulla oblongata sends a message to the rib cage muscles to contract.

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Breathing and Homeostasis

• You have some conscious control over your breathing—when you swim or play an instrument, for example—but breathing is not purely voluntary.

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• Your nervous system has final control of your breathing muscles whether you are conscious or not.

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Breathing and Homeostasis

• Breathing is initiated by the breathing center in the part of the brain stem called the medulla oblongata.

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• Sensory neurons in or near the medulla and in some large blood vessels gather information about carbon dioxide levels in the body and send the information to the breathing center.

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• When stimulated, the breathing center sends nerve impulses that cause the diaphragm and chest muscles to contract, bringing air into the lungs.

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