Respiration

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 • 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 Image taken without permission from http://bcs.whfreeman.com/thelifewire/

8. Respiratory Systems: Gills • Why is countercurrent exchange an effective way to get O2 from water? (especially compared to concurrent flow) Image taken without permission from http://bcs.whfreeman.com/thelifewire/

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 Image taken without permission from http://bcs.whfreeman.com/thelifewire/

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 equivalentto 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 Image taken without permission from http://bcs.whfreeman.com/thelifewire/

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 5 slides left

33. Question… • How would holding your breath affect your blood pH? • It would cause pH to drop since CO2 is not being eliminated 4 slides left

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 3 slides left

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 2 slides left

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 1 slide left

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! 