Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

40. Circulatory System

Gas Exchange

General Biology

40. Circulatory System

Gas Exchange

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0:47 minutes

Problem 12b

Textbook Question

During exercise, the cardiovascular system must supply muscles with large amounts of oxygen and fuel and get rid of a lot of waste.
How do the cardiovascular systems of athletes respond to prolonged exercise?
When athletes exercise, what is the primary physiological variable responsible for their sustained increase in ventilation rate?
a. Decreased blood PO₂
b. Increased blood PCO₂
c. Increased blood pH
d. Increased body temperature

Verified step by step guidance

Understand that during exercise, the cardiovascular system must efficiently deliver oxygen and nutrients to muscles and remove waste products like carbon dioxide (CO2).

Recognize that the primary physiological variable responsible for increased ventilation rate during exercise is related to the body's need to expel CO2, a waste product of metabolism.

Consider the role of blood gases: Partial pressure of carbon dioxide (PCO2) increases in the blood during exercise due to enhanced metabolic activity, which stimulates ventilation to expel excess CO2.

Analyze the options: (a) decreased blood PO2, (b) increased blood PCO2, (c) increased blood pH, (d) increased body temperature. Increased blood PCO2 is directly linked to increased ventilation rate as the body attempts to maintain homeostasis by removing CO2.

Conclude that the primary physiological variable responsible for the sustained increase in ventilation rate during exercise is the increased blood PCO2, as it triggers the respiratory centers in the brain to increase breathing rate to expel CO2.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Cardiovascular System Adaptations

During prolonged exercise, the cardiovascular system adapts by increasing heart rate and stroke volume to enhance blood flow to muscles. This ensures efficient delivery of oxygen and nutrients while facilitating the removal of metabolic wastes. Athletes often have a more robust cardiovascular response due to training, which improves their endurance and performance.

Ventilation Rate Regulation

Ventilation rate, or the rate of breathing, is primarily regulated by the levels of carbon dioxide (PCO2) in the blood. During exercise, increased muscle activity leads to higher CO2 production, which stimulates chemoreceptors to increase ventilation rate to expel excess CO2 and maintain blood pH balance. This physiological response is crucial for sustaining prolonged physical activity.

Blood Gas Levels and pH

Blood gas levels, including PO2 and PCO2, and blood pH are critical in respiratory physiology. During exercise, increased PCO2 due to heightened metabolic activity is the primary driver for increased ventilation. This helps maintain homeostasis by preventing acidosis, ensuring that oxygen delivery and CO2 removal are optimized to meet the demands of active muscles.

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Related Practice

Textbook Question

What is the primary feedback used by the brain to control breathing?

a. Heart rate

b. Partial pressure of O₂

c. Blood pH, which indicates O₂ level

d. Blood pH, which indicates CO₂ level

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Textbook Question

What are two advantages of breathing air, compared with obtaining dissolved oxygen from water? What is a comparative disadvantage of breathing air?

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Textbook Question

During exercise, the cardiovascular system must supply muscles with large amounts of oxygen and fuel and get rid of a lot of waste.

How do the cardiovascular systems of athletes respond to prolonged exercise?

During athletic training, the oxygen–hemoglobin dissociation curve

a. Shifts to the right, unloading more oxygen to tissues.

b. Shifts to the right, unloading less oxygen to tissues.

c. Shifts to the left, unloading more oxygen to tissues.

d. Shifts to the left, unloading less oxygen to tissues.

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views

Textbook Question

Carbon monoxide (CO) is a colorless, odorless gas found in furnace and automobile engine exhaust and cigarette smoke. CO binds to hemoglobin 210 times more tightly than does O₂. CO also binds with an electron transport protein and disrupts cellular respiration. Explain why CO is such a deadly gas.

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Textbook Question

Partial pressure reflects the relative amount of gas in a mixture and is measured in millimeters of mercury (mm Hg). Llamas are native to the Andes Mountains in South America. The partial pressure of O₂ (abbreviated P_O₂) in the atmosphere where llamas live is about half of the P_O₂ at sea level. As a result, the PO₂ in the lungs of llamas is about 50 mm Hg, whereas that in human lungs at sea level is about 100 mm Hg. A dissociation curve for hemoglobin shows the percentage of saturation (the amount of O₂ bound to hemoglobin) at increasing values of P_O₂ As you see in the graph below, the dissociation curves for llama and human hemoglobin differ. Compare these two curves and explain how the hemoglobin of llamas is an adaptation to living where the air is 'thin.'

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Textbook Question

Mountain climbers often spend weeks adjusting to the lower partial pressure of oxygen at high altitudes before and during their ascent of high peaks. During that time, their bodies begin to produce more red blood cells. Some runners and cyclists prepare for competition by training at high altitudes or by sleeping in a tent in which P_O₂is kept artificially low. Explain why this training strategy may improve an athlete's performance.

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Textbook Question

One of the many mutant opponents that the movie monster Godzilla contends with is Mothra, a giant mothlike creature with a wingspan of 7–8 m. Science fiction creatures like these can be critiqued on the grounds of biomechanical and physiological principles. Focusing on the principles of gas exchange that you learned about in this chapter, what problems would Mothra face? Why do you think truly giant insects are improbable?

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Textbook Question

E-cigarettes pose a dilemma for public health officials. Because e-cigarettes produce fewer toxic chemicals than regular cigarettes, they may be a safer alternative for people who want to quit smoking but still crave nicotine. On the other hand, e-cigarettes may encourage nicotine addiction among teenagers. Evaluate the scientific evidence. Are e-cigarettes an effective aid for quitting cigarettes? What evidence supports the assertion that e-cigarettes are especially harmful to adolescents? The Centers for Disease Control website is a good place to start. cdc.gov/tobacco/basic_information/e-cigarettes/

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