Lecture 32/33: Control of Ventilation Flashcards
What are the 3 main areas for neural control of respiration?
1) medullary control center: dorsal respiratory group (nucleus tractus solitarius) = inspiration, ventral respiratory group = expiration
2) apneustic center - slower, longer breaths
3) pneumotaxic center - inhibits apneustic center. shortens/inhibits inspiration
Describe the nerve output of the phrenic nerve during inspiration and expiration
Phrenic nerve output to diaphragm is very active during inspiration, slight burst during expiration
Discuss the central chemoreceptors. What are they sensitive to? What modulates their sensitivity?
Sensitive to CO2 only. modulated by pH. Low pH results in higher sensitivity. stimulation by acidosis = release of serotonin, stimulation by alkalosis = release of GABA
Where are the peripheral chemoreceptors located? What modulates their sensitivity?
Located in the carotid and aortic bodies. Only O2 sensors, also sense CO2 and pH. high CO2, low pH will increase sensitivity to O2. low O2 will increase firing, high O2 won’t affect much. high Co2 alone, low pH alone will increase firing rate
How do glomus cells work? What happens when there is a change in pH, PCO2, or PO2?
Essentially, there is inhibition of K+ channels, depolarization, and release of neurotransmitter through nerves 9 and 10. low PO2 = more cAMP, more reduced glutathione, lower open probability of K+ channels. low pH inhibits NHE exchanger, more PCO2 = more H+, these also inhibit K+ channel.
Describe the 5 chest wall/lung reflexes
Hering-Breuer reflex - inspiration inhibitory reflex, senses stretch of thoracic cavity via vagus nerve
Diving reflex - cold water on facial and nasal receptors causes breath hold and bradycardia
Superficial larynx reflex: smoky room - irritants cause coughing, apnea, expectoration
sniff reflex - mechanoreceptors in pharynx and nasopharynx draws material to pharynx
Deep larynx receptors - control muscle fibre activation
Describe the 4 sensory receptors & reflexes
Fast-adapting pulmonary stretch receptors - activated by dust/irritants/smoke/histamine - cause coughing, airway resistance, apnea
Slow adapting pulmonary stretch receptors - activated by lung stretch, myelinated vagal nerves delay onset of next breath
Juxtaalveolar receptors - respond to chemical or mechanical stimulus, located in parenchyma. unmyelinated vagal fibres that cause shallow breathing, bronchoconstriction, mucus secretion to increase turublence
Somatic receptors - sense stretch, lung volume, change force of breathing
What is Cheyne-Stokes breathing?
lack of cerebral blood flow, lag in detection of low or high CO2 so high amplitudes of breathing patterns, O2, and CO2 levels
Apneustic breathing?
long periods of inspiration, short expiration. loss of inspiratory inhibition
What are the 2 forms of sleep apnea
obstructive - weight of tissue causes collapse of airway
central - brani stopped drive to breathe
What is Ondine’s curse?
no automatic control of breathing, requires conscious thought. need ventilator
