Respiratory Lecture 7&8 Flashcards
What is the central controller of respiratory system in brain?
Pons, medullar, other parts of brain
Where does the central controller send output, receive input?
Output- effectors- respiratoyr muscles
Sensors- chemoreceptors, lung and other receptors
What is the brain stem’s role in respiration?
- Involuntary control: periodic inspirationa nd expiration controlled by neurons in pons and medulla (respiratory center)
- medullar has dorsal group which triggers inspiration
- ventral group is mainly with expiration
- normally quiet except during active expiration
- Rage or fear can alter breathing as well
What is cortical breathing?
- Voluntary
- intentional hyperventilation- reduce CO2, tetany, seizures, fainting
- Intentional hypoventilation- breath holding spells in toddlers
- co2 retention, hypoxemia, syncope, seizure
What are the 2 chemoreceptors to help regulate breathing?
Central chemoreceptors
peripheral chemoreceptors
What is role of central chemoreceptors in breathing?
- Located near the ventral surface of medulla
- Surrounded by ECF, and responds to changes in H concentration
- when blood pCO2 rises, more CO2 diffuses into CSF, liberates H ions, which stimulate chemoreceptors
- Resulting hyperventilation reduces pco2 in blood and CSF
- CENTRAL CHEMORECEPTORS ARE NOT SENSITIVE TO CHANGES IN PO2 of blood
What are peripheral chemoreceptors?
- Located in:
- carotid bodies at bifurcation of common carotid arteries
- aortic bodies above and below aortic arch
- Respond to:
- arterial pO2
- pH
- arterial pCO2
- Very little response until arterial pO2 is reduced below 100 mmHg, then rate rapidly increases.
What is ventilatory response to CO2?
Alveolar ventilation increases with increasing pCO2
- Decreased pH in CSF
- Narcotic suppress respiration, but also reduce slope of reponse to changes in pCO2 (shifts response to right, more CO2 needed to elicit response)
What are pulmonary stretch recepotrs?
- Lie between airway smooth muscle
- respond to lung distension in sustained fashion- slow adapting
- effect slows respiratory frequency by increasing expiratory tim
- HERING-BRUER REFLEX
- Important in newborns
- in adults triggered at high TV (>1L) during exercise
- HERING-BRUER REFLEX
What are irritant receptors in the lung?
- Lie b/w epithelial cells
- stimulated by noxious gases, cigarette smoke, inhaled dusts, cold air
- vagus- bronchoconstriciton, hyperpnea
- rapidly adapting
What are juxtacapillary receptors?
- in alveolar walls close to capillaries
- stimulated by hyperinflation of lungs and various cehmical stimuli
- reflexive rapid, shallow breathing occurs as result
Ventilatory response is more sensitive to _____ when combined with _____
hypoxemia; hypercarbia
What is ventilatory resposne to exercise?
- Oxygen consumption increases
- oxygen i ssupplied by increading ventilation
- CO2 production increases, blown off by increased ventilation
- Mean arterial pO2 and pCO2 do NOT change during exercise
- CO and pulmonary blood flow increases
- recruitment of pulmonary vessels decreases PVR and enhances blood flow
- Hb dissociation curve shifts to RIGHT, enhancing o2 delivery to tissues
Fetal circulation changes at birth?
- In utero- placental circulation in parallel with peripheral
- pO2 is lowat 30 mmHg
- Ductus arteriosus shunts blood from PA ot descneding aorta
- Newborn baby takes first breath
- dramatic fall in PVR
- lung expansion decreasing extra alveolar resistance
- oxygen increases
- increased pulmonary blood flow
- LA pressure rises, causing foramen ovale to close
- dramatic fall in PVR
What is cheyne stokes breathing?
- APnea for 10-20 seconds separated by equal periods of hyperventilation with waxing and waning tidal volumes
- Occurs in severe hypoxemia, high altitudes, during deep sleep, brain injury
