1. Respiration
AP Biology
Unit 6

2. Types of Respiratory Systems
Animals typically do gas exchange through one (or more) of the following means:
Skin (body surface)
Gills (internal or external)
Lungs
Tracheal System

3. Respiratory Media
Both air and water can serve as respiratory media (what is being “breathed” in)
Ex. Fish respire water, humans respire air
What are the advantages of respiring air versus water?

4. Air as a respiratory media
Advantages
Lighter
Contains more O2
Disadvantages
Membranes dry out more easily (moisture needed)

5. Water as a media Advantages Disadvantages
Keeps membrane moist (so they continue functioning properly)
Disadvantages
Heavier
Contains less O2

6. Respiratory Systems: Gills
Fish use their gills as a respiratory surface
Water flows in through mouth, across the gills, then out through the operculum
As the water flows across the gills, O2 diffuses into the capillaries in the gills, CO2 diffuses out.

7. Respiratory Systems: Gills
Water flows across the gills in the opposite direction as the blood flowing in the capillaries = Countercurrent Flow
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8. Respiratory Systems: Gills
Why is countercurrent exchange an effective way to get O2 from water? (especially compared to concurrent flow)
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9. Respiratory Systems: Gills
Countercurrent flow is an effective way to get O2 because as the blood flows, it always meets water that is more highly oxygenated  allows O2 to diffuse into the blood along the entire length of the gills
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10. Tracheal Systems Insects have spiracles which open up to the outside
Air flows in from the spiracles and through the tracheae
The tracheal system is so extensive that this allows air to flow right next to the body cells

11. Question…
How does the tracheal system allow insects to maintain a high metabolic rate despite having an open circulatory system?
They don’t use their circulatory system to transport O2 to cells– flows directly from tracheae to cells  open circulatory system not a factor

12. Respiratory Systems: Birds
Birds have air sacs and lungs
Air sacs = for storing air (no gas exchange occurs here)
Lungs – where gas exchange (O2 into blood and CO2 out) occurs

13. Respiratory Systems: Birds
Birds have one way flow through their lungs
Animation

14. Question…
How does a bird’s respiratory system allow it to maintain high levels of activity, even at high altitudes (where there is less O2)?
One way flow means that the most oxygenated air is always flowing across the lung surfaces
There is no “old/stale” air left over in the lungs that takes up space

15. Mammalian Respiratory System
Pathway of air
Nasal cavity & mouth  pharynx (back of throat  trachea  bronchi  bronchioles  alveoli

16. Mammalian Respiratory System
Trachea
Windpipe
Lined with rings of cartilage for structural support
Bronchi
Main branches leading from trachea
Bronchioles
Smaller branches (no cartilage rings)

17. Alveoli Air sacs with very thin walls Surrounded by lung capillaries
Where gas exchange occurs
Random fact: You have approximately 300 million alveoli in your lungs– surface area is equivalent to ¼ of a basketball court

18. Inhalation Inhalation = taking air into the lungs
Diaphragm contracts (flattens)  space in chest cavity expands (pressure lowered)  air from outside is sucked in (flows from high to low pressure)

19. Exhalation Exhalation = air leaves the lungs
Diaphragm relaxes (moves up)  less space in chest cavity  air is pushed out of lungs

20. Diffusion of Gases in the Alveoli
Diffusion of O2 and CO2 in the lungs (alveoli) is caused by differences in partial pressure
Partial pressure = pressure due to one particular gas (kind of like concentration)
PO2 = partial pressure due to O2
PCO2 = partial pressure due to CO2

21. Diffusion of Gases
Oxygen diffuses into the capillaries from the alveoli (PO2 in the capillaries is lower than PO2 in the alveoli)
CO2 diffuse into the alveoli from the capillaries (PCO2 in the capillaries is higher than PCO2 in the alveoli)

22. Transport of Oxygen in the Blood
Oxygen is transported by hemoglobin in red blood cells
Each hemoglobin molecule can carry 4 O2 molecules
Cooperative binding = once the first O2 binds, the next 3 are able to bind more easily

23. Bohr Effect
pH changes hemoglobin’s affinity (ability to bind) for oxygen  Bohr effect
At lower pHs, hemoglobin doesn’t bind O2 as well  lets it go into the surrounding tissues

24. Question…
Why would it make sense to drop off more O2 when the pH is lower?
Lower pH is due to lactic acid from fermentation
This means the cells in that region need more O2  hemoglobin drops it off more readily

25. Hemoglobin affinity
Certain organisms also have hemoglobin with a high affinity for oxygen
Fetus has a higher affinity for O2 compared to its mother
Llamas have a higher affinity for O2 compared to animals who live at sea level
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26. Question…
Why would a fetus have hemoglobin with a higher affinity for O2 than its mother?
The only way for a fetus to get O2 is from its mother (umbilical cord)  it has to be able to have hemoglobin that can “grab” O2 from its mother’s bloodstream

27. Question…
Why would a llama have hemoglobin with a higher affinity for O2 compared to other mammals?
At higher altitudes, there is less O2 in the air (lower PO2)  llamas have to be able to grab more O2 at a lower PO2 to get enough to survive.

28. Transport of CO2
CO2 is mostly transported as HCO3- (bicarbonate ions) in the blood plasma
After CO2 diffuses into the blood from the body cells, carbonic anhydrase (enzyme in RBC) converts CO2 into bicarbonate ions

29. Transport of CO2
When the bicarbonate reaches the lungs, the carbonic anhydrase converts it back into CO2 gas  it diffuses out into the alveoli

30. Control of Respiration
Regulated by brain (medulla oblongata and pons) that controls the diaphragm and rib muscles to change rate or depth of breathing
Sensors send messages to brain from elsewhere in body

31. Control of Respiration
Messages include those about:
O2 concentration (only when very low)
pH of blood (related to CO2 concentration)

32. Control of Respiration
CO2 / blood pH has a much stronger effect on breathing rate than O2 levels
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33. Question… How would holding your breath affect your blood pH?
It would cause pH to drop since CO2 is not being eliminated
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34. Marine Mammal Diving Reflex
When marine mammals dive, their heart rate goes way down– sometimes it goes down to 3 or 4 beats a minute
This is the diving reflex
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35. Marine Mammal Diving Reflex
Blood is sent primarily to the brain, eyes and adrenal glands
Blood flow to muscles is shut off – it just uses the O2 stored in the myoglobin in muscles
Myoglobin is an oxygen carrying molecule in muscles
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36. Marine Mammal Diving Reflex
What adaptations does the marine mammal have to allow them to stay underwater for a long time (sometimes up to 2 hrs)?
Lots of myoglobin to store O2 in muscles
More blood to store more O2
Huge spleen
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37. Human Diving Reflex Humans have a similar reflex
When your face is submerged, your heart rate goes down
Might be a protective response during birth when the pressure can prevent O2 from getting to the baby from the umbilical cord  slowing down blood flow slows down O2 depletion in blood
Last slide! 