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
Adaptation of ventilation to high altitude?
- Hypoxemia occurs at high altitude
- severe reduciton in pO2 of inspired and alveolar air
- pulmonary vasoconstriciton due to hypoxemia
- high altitude sickness, attributed to hypoxia
- adaptaion by hyperventilation in response to hypoxemia levels leads to resp alkalosis
- polycythemia d/t hypoxic stimulation of erythropoietin producion, increasing RBC production
- increased 2,3, DPG shift to right, enhanving O2 release
What is forced expiratory volume?
Volume of gas exhaled by forced expiraiton after full inspiration in 1 second.
Also called FEV1
What is forced vital capacity?
Used to indicate that expiration is forces. May be slightly less than vital capacity
What does FEV1/FVC ratio tell us?
Gives us valuable information regarding fraction of FVC exhaled in first second
What is a normal FEV1/FVC ratio?
80%
What does FEV1/FVC ratio show in obstructive diseases?
Reduced (<80%)
Both FEV and FVC are lowered, but FEV lowered more significantly than FVC
What is FEV1/FVC in restrictive dieases?
Ratio may actually be increased. However, FVC volume is down and so is FEV1, but not as significant, thereby increasing ratio
What is characteristics of obstructive disease?
- FEV1 decreased
- FVC unchanged or reduced but less so
- ratio FEV1/FEC is decreased
- Asthma
- Chornic bronhicits
- emphysema
What is characteristic of restrictive disease?
- FVC decreased
- even if FEV1 reduced, ratio of FEV1/FVC is normal or may be increased
- ex:
- interstitial fibrosis
- sarcoidosis
- scoliosis
- weakness
Expiratory flow-volume curves are typiclally ___ ___ in obstructive disease
scooped out
What are characteristics of chornic bronchitis?
- “Blue bloater”
- blue
- not dyspneic
- cor pulmonale
- edematous
- reduced drive to breath
- severe hypoxemia
- elevated pCO2
- polycythemia
What are characteristics of emphysema?
- “pink puffer”
- increased drive to breath
- pink
- dyspneic
- no cor pulmonale
- not edematous
- mild hypoxemia
- normal pCO2
- normal RBC mass
