Mechanism of Respiration and Regulation of Respiration
Mechanism of Respiration:
Cells in the body require oxygen to survive, while carbon dioxide is a by-product of cellular respiration. The respiratory system ensures oxygen is taken in from the air and carbon dioxide is expelled from the body.
Inhalation:
- The diaphragm moves downward toward the abdomen.
- Rib muscles pull the ribs upward and outward, enlarging the chest cavity and drawing air into the lungs through the nose or mouth.
- Air fills the alveoli, and oxygen diffuses into the blood through capillaries lining the alveolar walls.
- Oxygen binds to hemoglobin in red blood cells and is transported to tissues via arteries.
Exhalation:
- The diaphragm moves upward, and chest wall muscles relax, reducing chest cavity size.
- Air is expelled from the lungs through the nose or mouth.
- In the tissues, oxygen is released from hemoglobin and enters the cells.
- Carbon dioxide produced by cells diffuses into capillaries, dissolves in plasma, and returns to the heart via veins, then to the lungs to be exhaled.
Regulation of Respiration:
Neural Regulation:
- Phrenic and intercostal nerves: Control activity of the diaphragm and external intercostal muscles.
- Medulla and Pons: Neural centers in the medulla set the basic rhythm of breathing. The medulla contains a self-exciting inspiratory center (pacemaker) and an expiratory center. Pons centers smooth out the rhythm.
- Eupnea: Normal respiratory rate of 12–15 respirations per minute.
- Hyperpnea: Increased rate and depth of breathing during exercise due to higher neural stimulation of respiratory muscles.
Non-Neural Factors:
Hypoventilation: Slow or shallow breathing allows CO2 to accumulate, restoring pH when blood becomes slightly alkaline.
Physical factors: Activities such as talking, coughing, exercise, and increased body temperature can modify breathing rate and depth.
Volition (conscious control): Voluntary control is limited; the brain overrides voluntary signals if oxygen is low or blood pH falls.
Emotional factors: Emotional stimuli via the hypothalamus can modify respiratory rate and depth.
Chemical factors: Levels of CO2, O2, and blood pH are major regulators. Increased CO2 and decreased pH stimulate faster and deeper breathing. Low oxygen levels stimulate breathing when critically low.
Hyperventilation: Rapid breathing removes excess CO2, reducing carbonic acid to restore normal blood pH.
Detailed Notes
For PDF style full-color notes, open the complete study material below: