Control of Breathing

Control of respiration• Neural regulation:- The activity of the

respiratory muscles (diaphragm and external intercostals) is regulated by nerve impulses transmitted to them from the brain by the phrenic and intercostal nerves

- The neural centers that control respiratory rhythm and depth are located in the medulla and pons

Medulla and Pons

• The medulla sets the basic rhythm of breathing, contains a self-exciting inspiratory center, as well as other respiratory centers

• The pons centers appear to smooth out the basic rhythm of inspiration and expiration set by the medulla

• Medulla and pons maintain a impulse of 12-15 respirations/min

Factors influencing respiratory rate/depth

• Physical factors: talking, coughing, body temperature and exercise

• Volition (conscious control): Respiratory centers will ignore messages from the brain when the oxygen supply in the blood is getting low or blood pH is failing

• Emotional factors: fear, happiness, surprise

• Chemical factors: the levels of carbon dioxide (more important) and oxygen in the blood

- Increased level of CO2 and decreased level of pH leads to increase in the rate and depth of breathing

- Changes in O2 concentration in the blood are detected by chemoreceptors in the aorta and carotid artery

Factors influencing respiratory rate/depth

pH factors

• Low pH: breathe more deeply and more rapidly- this action blows off more CO2 and decrease the amount of carbonic acid

• High pH: breathe more shallow and slow- this action allows CO2 to accumulate in the blood

Hyperventilation

• Fast, deep breathing• Often brought on by anxiety attack, frequently

leads to brief period of apnea, brief stop of breathing, until CO2 builds up in the blood again

• Cyanosis: when breathing stop for a extended period of time

Nonrespiratory Movement• Sneezing: Involves using the uvula

to close the oral cavity off from the pharynx in order to clear the upper respiratory passages

• Coughing: Blast of upward rushing air that clears the lower respiratory passages

• Hiccupping: Sudden inspirations resulting from spasms of the diaphragm

• Yawning: A very deep inspiration formerly believed to be triggered by low oxygen

Nonrespiratory Movement

• Crying: Primarily an emotionally induced mechanism that involves release of air in a number of short breaths

• Laughing: An emotionally induced response that produces air movements similar to crying

Nonrespiratory Movement