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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1:56 minutes

Problem 5

Textbook Question

When you inhale, the diaphragm
a. Relaxes and moves upward.
b. Relaxes and moves downward.
c. Contracts and moves upward.
d. Contracts and moves downward.

Verified step by step guidance

Understand the role of the diaphragm in breathing: The diaphragm is a dome-shaped muscle located below the lungs. It plays a crucial role in the process of inhalation and exhalation by changing the volume of the thoracic cavity.

Recall the mechanics of inhalation: During inhalation, the thoracic cavity needs to expand to allow air to flow into the lungs. This expansion is achieved by the diaphragm's movement and the intercostal muscles.

Determine the diaphragm's action during inhalation: The diaphragm contracts during inhalation, which causes it to flatten and move downward. This increases the volume of the thoracic cavity and decreases the pressure inside, allowing air to flow into the lungs.

Eliminate incorrect options based on the diaphragm's movement: Options that describe the diaphragm relaxing or moving upward are incorrect because relaxation occurs during exhalation, not inhalation.

Select the correct answer: The correct description of the diaphragm's action during inhalation is that it contracts and moves downward.

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Key Concepts

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

Diaphragm Function

The diaphragm is a dome-shaped muscle located at the base of the thoracic cavity. During inhalation, it contracts and moves downward, increasing the volume of the thoracic cavity and allowing air to flow into the lungs. Understanding this function is crucial for grasping how breathing mechanics operate.

Inhalation Process

Inhalation is the process of taking air into the lungs, which occurs when the diaphragm contracts and moves downward. This contraction creates a negative pressure in the thoracic cavity, drawing air in through the respiratory tract. Recognizing this process is essential for understanding respiratory physiology.

Pressure Changes in Breathing

Breathing involves changes in pressure within the thoracic cavity. When the diaphragm contracts and moves downward, the volume of the cavity increases, leading to a decrease in pressure relative to the outside atmosphere. This pressure differential is what drives air into the lungs during inhalation.

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Textbook Question

When you hold your breath, which of the following first leads to the urge to breathe?

a. Falling CO₂

b. Falling O₂

c. Falling pH of the blood

d. Rising pH of the blood

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Textbook Question

Which of the following promotes oxygen release from hemoglobin?

a. A decrease in temperature

b. An increase in O₂ level.

c. A decrease in pH

d. A decrease in carbonic anhydrase activity

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Textbook Question

When you hold your breath, which of the following blood gas changes first leads to the urge to breathe?

a. Rising O₂

b. Falling O₂

c. Rising CO₂

d. Falling CO₂

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Textbook Question

Countercurrent gas exchange in the gills of a fish

a. Maintains a gradient that enhances diffusion.

b. Enables the fish to obtain oxygen without swimming.

c. Means that blood and water flow at different rates.

d. Allows O₂ to diffuse against its partial pressure gradient.

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Textbook Question

Explain how each parameter in Fick's law of diffusion is reflected in the structure of the mammalian lung.

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Textbook Question

Frog lungs have a smaller surface area for gas exchange than mammalian lungs. How do frogs compensate for this difference?

a. Frog tissue absorbs more oxygen from the blood than mammalian tissue does.

b. Frogs breathe more quickly than mammals.

c. Frogs also obtain oxygen via diffusion across the skin.

d. Frog lung tissue has a greater density of capillary beds than mammalian lung tissue.

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Textbook Question

Compared with the interstitial fluid that bathes active muscle cells, blood reaching these cells in arterioles has a

a. Higher PO₂.

b. Higher PCO₂.

c. Greater bicarbonate concentration.

d. Lower pH.

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Textbook Question

Carp are fishes that thrive in stagnant-water habitats with low oxygen partial pressure. Compared with the hemoglobin of many other fish species, carp hemoglobin has an extremely high affinity for O₂.

Draw an oxygen–hemoglobin equilibrium curve showing separate lines for carp and a fish that lives in water with a higher oxygen partial pressure.

Explain why they differ.

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