Need help on 2, 3a, 3b, & 4 Graph 2 The effect on ventilation of breathing low-o

Question

Need help on 2, 3a, 3b, & 4

Graph 2 The effect on ventilation of breathing low-oxygen mixtures. Graph 3 Effects on ventilation of increasing carbon dioxide in inspired air. Minute ventiliation (y-axis) is a measure of the amount of air breathed into and out of the lungs per minute. An increase in ventilatory drive would thus increase minute ventilation. v Recall that arterial P02 & Pco2 levels are important determinants of 02 and CO2 blood content 5. Does Graph 2 show how breathing affects or how PO2 affects breathing?

Explanation / Answer

2. PCO2 has more effect on the ventilation due to the changes in the ventilation increases exponentially with little change in the PCO2. But the change in the ventilation is very less with increase in PO2

3. a. This is mainly achieved by measuring the carbon dioxide content of the blood; normally, a high carbon dioxide concentration signals a low oxygen concentration, as we breathe in oxygen and breathe out carbon dioxide at the same time, and the body's cells use oxygen to burn fuel molecules, making carbon dioxide as a by-product. Low carbon dioxide levels cause the brain's blood vessels to constrict, resulting in reduced blood flow to the brain and lightheadedness. The gases in the alveoli of the lungs are nearly in equilibrium with the gases in the blood.

Hyperventilation has little effect on arterial pO2 and almost no effect on oxygen saturation which is nearly 100% under normal circumstances. Its main effect is to lower pCO2 and produce a respiratory alkalosis.

During the breath holding, the partial pressure of oxygen, of course, became lower, while the partial pressure of carbon dioxide increased. The body, in fact, possesses sensors that respond to changes in the blood of both oxygen (in the carotid and aortic bodies) and carbon dioxide (in the medulla).

b. The greater drop in the partial pressure of oxygen following hyperventilation also indicates that the hyperventilation did not affect the amount of oxygen in the blood very much. If the initial amount was about the same, the level would be expected to drop much further with a longer time of breath-holding.

Following hyperventilation, the breath-holding was for a longer period. But nonetheless the level of carbon dioxide did not rise higher than without the hyperventilation. This could only happen if the hyperventilation substantially reduced the amount of carbon dioxide in the blood.

4. When you breathe in and hold your breath, you have plenty of oxygen (which keeps you from blacking out) and little CO2. Over time, you run out of oxygen, but your blood CO2 levels rise. Your brain actually uses blood CO2 as an indicator for blood oxygen, so when CO2 levels are too high you are signaled to take a breath. If you find it hard to believe that low oxygen isn't what makes you want to breathe, consider carbon monoxide poisoning. It happens because you are breathing air with low oxygen, but the CO2 levels are the same and your body regulates your breathing as usual, so you die without ever realizing you were oxygen deprived.

When you exhale, you are forcing out the CO2. Why is holding your breath here harder? Because you've lowered your lung volume, the CO2 concentration of your lungs is now higher than your blood. Gasses diffuse from air to blood passively, from areas of high concentration to low. Lungs full of a breath of air have a higher oxygen concentration and lower CO2 concentration than your blood does, so oxygen flows into your blood and CO2 out of the blood. When the lungs become as concentrated as your blood with CO2, the CO2 no longer leaves your blood but builds up until your next breath.

empty lungs have lower volume, so fewer CO2 molecules are needed to get the same concentration as your blood. Thus, CO2 stops leaving your blood faster if the lungs are empty, meaning the CO2 levels in your blood reach critical faster and you need to breath sooner. Oxygen levels in your blood are likewise not rising fast enough (or at all, since you just exhaled), but it's the rise in CO2 that makes you gasp.

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