Respiratory Case Study

Priya is a healthy 22-year-old woman who just graduated from BUand has lived in Boston her whole life. She goes to Colorado tovisit a friend and together they drive to the top of Pike’s Peak, amountain with a peak elevation of approximately 14,000 ft above sealevel. While walking around taking pictures at the top of the peakPriya finds that she needs to sit down and catch her breath severaltimes, even though she is not exercising intensively. During thosebreaks she also notices that she is taking breaths much more deeplyand frequently than normal. She walks to the weather station torest and glances at a barometer hanging overhead. It reads 450mmHg. She thinks back to what she learned in BI 315 and realizesthat she may be experiencing altitudesickness.

1. Relative to sea level, the P in Priya’s (1) alveoli, (2)systemic arterial blood, and (3) systemic venous blood is:

A (1) lower; (2) lower; (3) the same.

B (1) the same; (2) the same; (3) the same.

C (1) lower; (2) lower; (3) lower.

D (1) lower; (2) the same; (3) the same.

2. From a mechanistic perspective, what caused Priya tobegin breathing more quickly immediately when she arrivedat the top of the peak?

A Increased peripheral chemoreceptor firing rate caused by lowarterial P.

B #Increased peripheral chemoreceptor firing rate caused by higharterial P.

C Decreased peripheral chemoreceptor firing rate caused by lowarterial P.

D Increased peripheral chemoreceptor firing rate caused by higharterial ​[H].

3. Once Priya has been at high altitude for a short time (e.g.,a few hours), what do you predict will be true of the P of hersystemic arterial blood?

A It will be lower than when she was at sea level.

B It will be higher than when she was at sea level.

4. Once Priya has been at high altitude for a short time (e.g.,a few hours), what do you predict will be true of the pH of hersystemic arterial blood?

A It will be lower than when she was at sea level.

B It will be higher than when she was at sea level.

C It will be the same as when she was at sea level.

5. Holding all else equal, which of the following chronicresponses do you predict would be homeostatic and reducethe severity of Priya’s altitude sickness?

A A decrease in the amount of hemoglobin contained in each redblood cell.

B A reduction in capillary density in her metabolically activetissues (e.g. her skeletal muscles).

C Increased tonic level of constriction of her respiratoryairways due to elevated levels of smooth muscle contraction.

D Biochemical changes in her cells that increase the averagenumber of ATPs generated per O molecule by cellularrespiration.

6. One chronic change that occurs robustly when humans move tohigh altitude is an increase in red blood cell differentiation,leading to a very high red blood cell count in the plasma(polycythemia). This was long regarded as a clearexample of adaptive physiological acclimation to low atmospheric Oin humans. However, it has recently been argued that this isactually an instance where a physiological change (increased redblood cell differentiation) that might be homeostatic in somecontexts (e.g. low tissue O levels due to low red blood cell countsafter a hemorrhage) might in fact be harmful in the wrongcontext (e.g. low tissue O levels due to low atmospheric O levels).Which of the following scenarios is a plausible reason whypolycythemia might be harmful to Priya’s overallhealth?

A Polycythemia reduces the partial pressure of O freelydissolved in the blood plasma.

B Polycythemia increases the viscosity of her blood, whichincreases resistance to flow, which increases blood pressure andputs added strain on the chambers of her heart when pumpingblood.

C Polycythemia shifts the O-hemoglobin dissociation curve of theblood to the left, increasing the affinity of the blood for O.

D Polycythemia reduces the oxygen carrying capacity of herblood.

7. After a while, Priya’s friend Tenzin comes to visit her atthe visitor’s center. Tenzin’s family immigrated to the US fromTibet before Tenzin was born. Even though Tenzin has never livedanywhere but Boston, Priya and Tenzin notice that he experiencesrelatively mild symptoms of altitude sickness when he arrives atPike’s Peak. They do some research and find recent peer-reviewedstudies by evolutionary biologists demonstrating that several humanpopulations, including ethnic Tibetans, have adapted to life athigh altitudes over the past several thousand years. This getsPriya and Tenzin thinking about what those physiologicaladaptations could plausibly be.

Respiratory Case Study.07

HomeworkAnswered

All of the following evolutionary adaptations might be predictedto improve the physiological performance of human populationsliving at high altitude EXCEPT:

A Globally lower resistance to blood flow through thevasculature due to the effects of local vasodilators such as nitricoxide.

B Increased ability of the kidneys to filter out and excrete HCOin the urine.

C Increased chest circumference and higher lung volumes(including tidal volume and vital capacity).

D Lower endogenous bursting rates in the neurons of therespiratory rhythmicity centers in the medulla.