BIOL 0800 Reading- Chapter 13 Flashcards Preview

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Flashcards in BIOL 0800 Reading- Chapter 13 Deck (113)
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What is the lower half of the VRG?

Expiratory neurons: important for large increases in ventilation like in exercise: active expiration through contraction


How is medullary inspiratory nerve activity modulated?

By the pons: apneustic center in lower pons, pneumotaxic center in uppon pons


What is the apneustic center?

In the lower pons: modulates medullary inspiratory activity, inhibitory to end inspiration


What is the pneumotaxic center?

In the upper pons: modulates apneustic center; smooths transition between inspiration/expiration


What are pulmonary stretch receptors for?

Cutting off inspiration: activated by large lung inflation: afferent nerve fibers send action potentials to inhibit medullary inspiratory neuron activity


What is the Hering-Breuer reflex?

When afferent nerve fibers from stretch receptors send action potentials to the brain to inhibit medullary inspiratory behavior and end inspiration; BUT only under conditions of large TV like during exercise


What are peripheral chemoreceptors for respiration?

Located in neck by common carotid arteries and in thorax on aortic arch: carotid bodies and aortic bodies (distinct from carotid and aortic baroreceptors); stimulated by decrease in arterial PO2 or increase in H+; provide excitatory input to medullary respiratory systems


What are the central chemoreceptors for respiration?

Located in medulla oblongata; provide excitatory input to medullary respiratory systems; stimulated by increase in H+


Why do changes in PCO2 trigger ventilation control reflex?

Mostly through increases or decreases in H+ concentration, which is detected by the central chemoreceptors and dealt with accordingly


Which chemoreceptors respond to H+ concentration changes, peripheral or central?

Peripheral for metabolic acidosis/alkalosis (not caused by CO2 changes), and central for respiratory acidosis/alkalosis (caused by CO2 changes)


How does H+ concentration affect chemoreceptor activity?

Increase in H+ increases chemoreceptor activation of medullary respiratory neurons, which increases respiration


What is associated with hyper/hypoventilation, metabolic alkalosis or acidosis?

Metabolic acidosis triggers hyperventilation (reduces arterial PCO2, so H+ back to normal); metabolic alkalosis triggers hypoventilation (increases arterial PCO2, so H+ back to normal)


Why doesn't arterial PCO2 increase during exercise?

Because arterial PCO2 depends on alveolar PCO2, and alveolar PCO2 depends on ratio of CO2 production to alveolar ventilation: ventilation increase proportionally with CO2 production during exercise, so no increase in alveolar PCO2


What is the limiting factor in strenuous exercise, ventilation or cardiac output?

CO: ventilation can increase enough to maintain PO2


Why is lactic acid partially responsible for hyperventilation during exercise?

Because it increases blood H+ concentration, which triggers the peripheral chemoreceptors to innervate the medullary inspiratory neurons to increase ventilation


How do J receptors act as a protective respiratory reflex?

In capillary walls/interstitium: stimulated by increase in lung interstitial pressure cased by fluid collection: rapid breathing, dry cough


What are the four kinds of hypoxia?

Hypoxic hypoxia (hypoxemia); anemic hypoxia (CO hypoxia); ischemic hypoxia; histotoxic hypoxia


What is hypoxic hypoxia?

Hypoxemia: arterial PO2 reduced


What is anemic hypoxia?

CO hypoxia; arterial PO2 normal but total oxygen content of blood is reduced because of inadequate numbers of RBCs, deficient Hb, or CO poisoning


What is ischemic hypoxia?

Blood flow to tissues is too low


What is histotoxic hypoxia?

Normal quantity of oxygen to tissues, but cell can't use it properly because of toxic agent interference


What is hypercapnea?

Increased retention of CO2 that leads to increased arterial PCO2


Why does ventilation-perfusion inequality affect O2 more than CO2?

Because of the oxyhemo dissoc curve: increasing ventilation doesn't really increase PO2 because of the curve, so PO2 remains low (hypoxia); but CO2 is linear: poor ventilation does increase PCO2, but then increased ventilation brings it right back down again