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7 Cards in this Set
- Front
- Back
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Cyclic respiration
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The site of rhythmic respiratory activity resides in the medullary region of the brainstem
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Medullary Rhythmiticity Area
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Medullary Inspiratory Neurons are main control of breathing
-Pons neurons influence inspiration, with Pneumotaxic area limiting inspiration and Apneustic area prolonging inspiration. -Lung stretch receptors limit inspiration from being too deep Medullary Expiratory Neurons -Only active with exercise and forced expiration Dorsal respiratory group primarily inspiratory activate phrenic nerves to diaphragm Ventral inspiratory group mixed inspiratory and expiratory neurons drive spinal neurons innervating intercostal and abdominal muscles and vagal input to accessory muscles of respiration |
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Control of rate and depth of respiration:
Arterial pO2 Arterial pCO2 Arterial pH |
Arterial PO2
-When PO2 is VERY low, ventilation increases -Level of alveolar pCO2 influences ventilation response (low pCO2 has less of a response in low pO2, and higher pCO2 has a higher respons to low pO2... synergistic relationship) Arterial PCO2 -The most important regulator of ventilation, small increases in PCO2, greatly increases ventilation Arterial pH -As hydrogen ions increase, alveolar ventilation increases, but hydrogen ions cannot diffuse into CSF as well as CO2 |
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Peripheral chemoreceptors
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Carotid and aortic bodies
- Detect changes in arterial PO2 and [H+] - Cause reflex stimulation of ventilation following significant fall in arterial PO2 (consider haemoglobin dissociation) or a rise in [H+] - Respond to arterial PO2 not oxygen content - Increased [H+] usually accompanies a rise in arterial PCO2 |
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Central chemoreceptors
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Medulla (on floor of 4th ventricle)
- Detect changes in [H+] in CSF around brain (from hydrated CO2 that has diffused into CSF and generated H+) - Cause reflex stimulation of ventilation following rise in [H+] (PCO2) |
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Ventilation and alveolar pCO2
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In a normal person, an increase in alveolar pCO2 generates an increase in pulmonary ventilation
This response is diminished when sleeping Also, for any given alveolar pCO2, a higher alveolar pO2 decreases ventilation In pregnancy, increases in serum progesterone decrease arterial pCO2. Therefore, progesterone is a stimulus for alveolar ventilation. |
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Respiratory reflexes
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Hering –Breuer inflation reflex
-Lung distension decreases inspiratory effort Hering –Breuer deflation reflex - Rapid lung deflation increases ventilation Both mediated by stretch receptors Cough and sneezing: a protective reflex -Receptors in larynx , the proximal tracheobronchial tree, lower part of the oropharynx, the smaller bronchi, the tympanic membrane and the external auditory meatus. -Respond to multiple stimuli |
