Respiratory System Control of Breathing

Respiratory Areas Groups of neurons in the brain stem which control breathing

Respiratory Areas Medullary rhythmicity center Includes two groups of neurons that extend throughout the medulla oblongata Dorsal respiratory group Stimulate muscles for inspiration (primarily the diaphragm) Control the depth of inspiration (forceful breathing) Ventral respiratory group Stimulate other respiratory muscles such as the intercostals and abdominals Some increase inspiration and some increase expiration Control the basic rhythm of breathing

Respiratory Areas Pontine Respiratory Group Also located in the brainstem (specifically the pons) Make connections with the medullary rhythmicity center

Factors Affecting Breathing Partial pressure The amount of pressure that each gas in air contributes to the total air pressure Proportional to the concentration of the gas Ex: air consists of 21% oxygen Atmospheric pressure of air is 760 HG So, .21 x 760 = 160 mm Hg, which is the partial pressure of O2

Factors Affecting Breathing Breathing rate and depth are affected by the partial pressure of oxygen and carbon dioxide in body fluids, the degree to which lung tissues are stretched and emotional state.

Factors Affecting Breathing Changes in partial pressure of carbon dioxide in the blood are mainly detected indirectly by chemoreceptors in the medulla oblongata (chemoreceptors actually detect increases in hydrogen ions that are released when carbonic acid (formed by carbon dioxide combining with water in the fluid of the brain) is ionized in the brain) Increases in carbon dioxide (either through breathing in carbon dioxide or as cellular waste) trigger breathing rate and tidal volume to increase which increase alveolar ventilation and return the partial pressure of carbon dioxide to normal

Factors Affecting Breathing Changes in partial pressure of oxygen are detected mainly by peripheral chemoreceptors in specialized structures (carotid bodies and aortic bodies) located in the walls of the carotid sinuses and the aortic arch When stimulated these structures send impulses to the respiratory system which then increases breathing rate and alveolar ventilation This process is not usually triggered until the partial pressure of oxygen falls below 50% of normal

Factors Affecting Breathing

Factors Affecting Breathing Inflation reflex Occurs when stretch receptors in the visceral pleura, bronchioles, and alveoli are stimulated by stretching of lung tissue Sends impulses to the respiratory center which then shortens the duration of inspiratory movements Prevents overinflation of the lungs during forceful breathing

Factors Affecting Breathing Gasping and rapid breathing are normal responses to stimuli such as fear, anger, and excitement

Factors Affecting Breathing Because control of respiratory muscles is voluntary breathing patterns can be consciously altered

Factors Affecting Breathing Hyperventilation Rapid and deep breathing Lowers the blood carbon dioxide level below normal May result in loss of consciousness due to a decrease in oxygen supply to the brain