Regulation of Respiration Flashcards
In the lung where would you find the most compliant alveoli?
base
In the lung, where would you find the lowest arterial BLOOD pressure?
apex
Optimal gas exchange occurs when ventilation is matched to perfusion
awesome
Ventilation to perfusion ratio at the apex is
3.3
ventilation to perfusion ratio at the base is
0.6
V/Q ratio is highest at the apex, therefore,
the apex is “over ventilated and under perfused”
PAO2 difference between apex and base
apex is 132 mmHg and base is 89 mmHg
PACO2 difference between apex and base
apex is 28 mmHg and base is 42 mmHg
difference in O2 in at apex and base
apex is 4 ml/min and base is 60 ml/min
difference in CO2 out at apex and base
apex is 8 ml/min and base is 39 ml/min
The apex has high PAO2 because
all ventilation and no perfusion so O2 is accumulating in the lung due to the high V/Q ratio and no perfusion is moving it away throughout the body
Where in the lung would you find the lowest PACO2?
apex
where in the lung would you find the lowest PAO2?
base
where in the lung would you find the highest O2 uptake?
base
blood leaving the lung has a PaO2 slightly less than PAO2
due to V/Q mismatch and shunting
Control of Respiration
- respiratory muscles require neural stimulation for contraction
- brain establishes the breathing rhythm and force of contraction
- changes in ventilation are assessed by feedback sensors which adjust neural output
Medullary Respiratory Centers:
A. Regulate rhythmicity
B. Activate respiratory muscles
C. Three regulatory regions such as —>
- DRG
- VRG
- Pre-Botzinger
DRG
dorsal diaphragm
primary inspiratory neurons that synapse with motor neurons for inspiration
VRG
insp and exp neurons active with forced breathing
maximal exercise (VICTORY)
Pre-botzinger
respiratory rhythm generation (BPM)
Pontine Respiratory Centers
A. Located in pons
B. two regulatory regions.
1. apneustic center
2. Pneumotaxic center
Pontine Respiratory Centers:
1. Apneustic Center
prolongs inspiration by activating neurons in the pre-botzinger complex apneusis: sustained contraction
Pontine Respiratory Centers:
2. pneumotaxic center
halts inspiration by sending inhibitory signals to the apneustic center and pre-botzinger complex
Respiratory Control Centers:
Cortex
A. voluntary: modifies respiration for speech, yawning, coughing or breath holding
B. respiratory reflexes will over ride voluntary actions
Respiratory Control Centers:
Limbic system and hypothalamus
A. regulate emotional responses
B. control breathing patterns during emotional states
what region of brain is responsible for voluntary rates of ventilation?
cortex
what region of brain is responsible for inspiration at rest?
dorsal respiratory group
what region of brain is responsible for maximal ventilation
ventral respiratory group
what region of brain is responsible for rate of ventilation?
pro-botzinger complex
During quiet expiration,
there is no AP bc it is passive
As ventilation increases until maximum ventilation with forced expiration,
the increased frequency of nerve signals creates bigger contractions
Peripheral chemoreceptors:
Arterial chemoreceptors
detect changes in?
location?
regulate?
A. detect changes in PaO2, PaCO2, and pH
B. primary sensitivity is to changes in PaO2
C. location: carotid artery and aortic arch
D. do not regulate minute-to-minute changes
E. emergency response for very low PaO2 levels
F. do not respond to changes in O2 content
Central Chemoreceptors:
regulate?
found?
sensitive?
permeable?
- central chemoreceptors regulate minute-to-minute ventilation
- found within the medulla near the VPG
- very sensitive to PCO2 and H+
- BBB is permeable to CO2
A major factor that quickly influences ventilation is:
pH of arterial blood
arterial PCO2
arterial PO2
arterial bicarbonate conc.
arterial PCO2
Lung (pulmonary) receptors:
1. pulmonary stretch receptors
found?
prevents?
A. found within smooth muscle of lung airways
B. stretching of lung induces activation of receptors which send inhibitory signals to the medullary centers
C. negative feedback mechanism prevents over-inflation
D. active when tidal volumes are high during max. exercise
Lung (pulmonary) receptors:
2. irritant receptors
found?
mechanism?
a. found in airway epithelial cells
b. noxious gas, duct, and cold air can activate receptors which leads to bronchoconstriction and rapid shallow breathing = protective mechanism limiting exposure
c. irritant receptors may play a role in asthma
d. activation of receptors can induce sneezing or coughing
e. mechanical stimulation during intubation can lead to laryngeal spasm
Lung (pulmonary) receptors:
3. pulmonary C fibers
a. near alveolar capillaries
b. stimulated by interstitial edema which activates the J reflex that leads to laryngeal closure, apnea, followed by rapid shallow breathing
c. may be responsible for rapid breathing seen in patients with pulmonary: emboli, edema, or pneumonia
d. may also be responsible for feeling short of breath in patients with congestive heart failure
Other Respiratory Receptors:
- nose and nasal passages
- upper airways: contain irritant receptors
- joint and muscle receptors: give feedback to medullary centers and to increase ventilation
the pneumotaxic center and stretch receptors will
a. inhibit neurons in the apneustic center
b. cause contraction of the diaphragm
c. activate internal intercostal nerves
d. cause respiratory arrest, then shallow breathing
a
EXAM QUESTION
what stimulates the highest rate of ventilation?
low O2 and high CO2
what is the most important variable regulating ventilation?
PCO2 and usually maintained within 3 mmHg
responses to changes in PO2 are greater with
hypercapnia
responses to changes in PCO2 are greater with
hypocapnia
Hyperventilation
decrease PCO2 and increase PO2 result in respiratory alkalosis
low PCO2 is hypocapnia
Hypoventilation
increase PCO2 and decrease PO2 result in respiratory acidosis
high PCO2 = hypercapnia
