mechanisms that control respiration

What controls the respiratory rhythm?

nuclei in the brainstem, integrate sensory information, determine rate and depth of breathing

How do respiratory neurons reach the breathing muscles?

travel from brainstem, innervate diaphragm via phrenic nerve, innervate intercostal muscles via intercostal nerves

What factors influence the respiratory nuclei?

lung stretch receptors, emotional input via limbic system and hypothalamus, voluntary control from primary motor cortex

What chemical factors influence breathing?

CO2 levels, O2 levels, H+ concentration

What do central chemoreceptors detect?

changes in CO2 only, located in the brainstem, drive most of the CO2 response

What do peripheral chemoreceptors detect?

changes in CO2 O2 and H+, located in carotid and aortic bodies

Why does PO2 normally not drive breathing?

PO2 is usually 95 to 104 mmHg, provides little stimulus for respiration, only becomes important when PO2 drops below 60 mmHg

What is the main driver of normal breathing?

PCO2, small changes cause large changes in ventilation, decreased PCO2 depresses breathing

How does increased PCO2 affect breathing?

increases ventilation, stimulates chemoreceptors, increases respiratory drive

How does decreased PCO2 affect breathing?

depresses breathing, reduces respiratory drive, increases blood pH

Why is PCO2 the key regulator of breathing?

CO2 and pH are inversely related, increased CO2 increases H+ and lowers pH, decreased CO2 decreases H+ and raises pH

How does CO2 affect blood pH?

increased CO2 forms carbonic acid, increases H+ and lowers pH, decreased CO2 reduces H+ and raises pH

Why does pH matter for breathing control?

small pH changes alter protein function, affects cellular function, requires rapid respiratory compensation

How is increased arterial PCO2 corrected?

detected by central and peripheral chemoreceptors, signals sent to medullary respiratory centers, ventilation increases to exhale more CO2

What percentage of the CO2 response comes from central chemoreceptors?

about 70 percent, located in the medulla, respond to CO2 mediated pH changes

What percentage of the CO2 response comes from peripheral chemoreceptors?

about 30 percent, located in carotid and aortic bodies, respond to CO2 O2 and H+

What is the result of increased ventilation during hypercapnia?

more CO2 exhaled, arterial PCO2 returns to normal, pH returns to normal

What factors can increase breathing rate and depth?

chemoreceptor activation, emotional stimuli, voluntary choice to increase breathing

What factors can decrease breathing rate and depth?

inhibitory signals from higher brain centers, decreased CO2, voluntary choice to slow breathing